PURITAN BENNETT CORP
SC 14D1, 1994-10-25
ORTHOPEDIC, PROSTHETIC & SURGICAL APPLIANCES & SUPPLIES
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<PAGE>
 
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                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
 
                               ----------------
 
                                 SCHEDULE 14D-1
 TENDER OFFER STATEMENT PURSUANT TO SECTION 14(D)(1) OF THE SECURITIES EXCHANGE
                                  ACT OF 1934
 
                               ----------------
 
                          PURITAN-BENNETT CORPORATION
                           (NAME OF SUBJECT COMPANY)
 
                              PB ACQUISITION CORP.
                          THERMO ELECTRON CORPORATION
                                   (BIDDERS)
 
                               ----------------
 
                    COMMON STOCK, $1.00 PAR VALUE PER SHARE
            (INCLUDING THE ASSOCIATED COMMON STOCK PURCHASE RIGHTS)
                         (TITLE OF CLASS OF SECURITIES)
 
                                  746299 10 6
                     (CUSIP NUMBER OF CLASS OF SECURITIES)
 
                               ----------------
 
                            SETH H. HOOGASIAN, ESQ.
                          THERMO ELECTRON CORPORATION
                                81 WYMAN STREET
                                 P.O. BOX 9046
                               WALTHAM, MA 02254
                                 (617) 622-1000
 
                                    COPY TO:
                             DAVID E. REDLICK, ESQ.
                                 HALE AND DORR
                                60 STATE STREET
                                BOSTON, MA 02109
                                 (617) 526-6000
 
         (NAMES, ADDRESSES AND TELEPHONE NUMBERS OF PERSONS AUTHORIZED
           TO RECEIVE NOTICES AND COMMUNICATIONS ON BEHALF OF BIDDER)
 
                               ----------------
                           CALCULATION OF FILING FEE
 
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 Transaction Valuation*: $315,386,883 Amount of Filing Fee**: $63,077.38
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 * For purposes of calculating fee only. This amount is based upon (a)
   11,914,965 outstanding shares of Common Stock, $1.00 par value per share
   (the "Shares"), of the Subject Company (excluding Shares owned by the
   Bidders), as reported in the Quarterly Report on Form 10-Q of the Subject
   Company for the quarter ended July 31, 1994, (b) 957,969 Shares reserved for
   issuance upon the exercise of options outstanding as reported in the Annual
   Report on Form 10-K of the Subject Company for the year ended January 31,
   1994 and (c) the price offered per Share.
** The amount of the filing fee, calculated in accordance with Regulation
   240.0-11 under the Securities Exchange Act of 1934, as amended, equals 1/50
   of one percent of the Transaction Valuation.
 
[_]    Check box if any part of the fee is offset as provided by Rule 0-
       11(a)(2) and identify the filing with which the offsetting fee was
       previously paid. Identify the previous filing by registration statement
       number, or the form or schedule and the date of its filing.
 
<TABLE>
     <S>                        <C>
     Amount Previously Paid:    Not applicable
     Form or Registration No.:  Not applicable
     Filing Party:              Not applicable
     Date Filed:                Not applicable
</TABLE>
 
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<PAGE>
 
  This Tender Offer Statement on Schedule 14D-1 relates to the offer by PB
Acquisition Corp., a Delaware corporation (the "Purchaser") and a wholly owned
subsidiary of Thermo Electron Corporation, a Delaware corporation (the
"Parent"), to purchase all of the outstanding shares of Common Stock, $1.00 par
value per share (the "Shares"), of Puritan-Bennett Corporation, a Delaware
corporation (the "Company"), and (unless, on or before the Expiration Date (as
defined below), the associated Common Stock Purchase Rights (the "Rights") have
been redeemed by the Company's Board of Directors) the Rights issued pursuant
to the Rights Agreement dated as of May 2, 1989, between the Company and United
Missouri Bank of Kansas City, N.A., as Rights Agent, at a purchase price of
$24.50 per Share (and associated Right), net to the seller in cash, without
interest thereon, upon the terms and subject to the conditions set forth in the
Offer to Purchase dated October 25, 1994 (the "Offer to Purchase"), a copy of
which is attached hereto as Exhibit 11(a)(1), and in the related Letter of
Transmittal (which, together with the Offer to Purchase, constitute the
"Offer"), a copy of which is attached hereto as Exhibit 11(a)(2). Unless the
context requires otherwise, all references in this Tender Offer Statement to
"Shares" shall be deemed to refer also to the Rights, and all references to
"Rights" shall be deemed to include all benefits that may inure to the
shareholders of the Company or to holders of the Rights pursuant to the Rights
Agreement.
 
ITEM 1. SECURITY AND SUBJECT COMPANY
 
  (a) The name of the subject company is Puritan-Bennett Corporation and the
address of its principal executive offices is 9401 Indian Creek Parkway,
Overland Park, Kansas 66225.
 
  (b) The exact title of the class of equity securities being sought in the
Offer is Common Stock, $1.00 par value per share, (including the associated
Common Stock Purchase Rights), of the Company. The information set forth in the
Introduction (the "Introduction") of the Offer to Purchase is incorporated
herein by reference.
 
  (c) The information set forth in Section 6 ("Price Range of Shares;
Dividends") of the Offer to Purchase is incorporated herein by reference.
 
ITEM 2. IDENTITY AND BACKGROUND
 
  (a)-(d) and (g) This Statement is filed by the Purchaser and the Parent. The
information set forth in Section 8 ("Certain Information Concerning the
Purchaser and the Parent") of the Offer to Purchase and in Schedule I
("Directors and Executive Officers of the Purchaser and the Parent") thereto is
incorporated herein by reference.
 
  (e) and (f) During the last five years, neither the Purchaser nor the Parent
nor, to the best knowledge of the Purchaser or the Parent, any of the persons
listed in Schedule I to the Offer to Purchase, (i) has been convicted in a
criminal proceeding (excluding traffic violations or similar misdemeanors) or
(ii) was a party to a civil proceeding of a judicial or administrative body of
competent jurisdiction and as a result of such proceeding was or is subject to
a judgment, decree or final order enjoining future violations of, or
prohibiting activities subject to, federal or state securities laws or finding
any violation of such laws.
 
ITEM 3. PAST CONTACTS, TRANSACTIONS OR NEGOTIATIONS WITH THE SUBJECT COMPANY
 
  (a) and (b) The information set forth in Section 8 ("Certain Information
Concerning the Purchaser and the Parent") and in Section 10 ("Background of the
Offer; Contacts with the Company") of the Offer to Purchase is incorporated
herein by reference.
 
ITEM 4. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION
 
  (a) The information set forth in Section 9 ("Source and Amount of Funds") of
the Offer to Purchase is incorporated herein by reference.
 
                                       2
<PAGE>
 
  (b) and (c) Not applicable.
 
ITEM 5. PURPOSE OF THE TENDER OFFER AND PLANS OR PROPOSALS OF THE BIDDER
 
  (a)-(g) The information set forth in the Introduction, Section 10
("Background of the Offer; Contacts with the Company"), Section 11 ("Purpose of
the Offer; the Merger; Plans for the Company"), and Section 13 ("Possible
Effects of the Offer on the Market for the Shares, NNM Quotation and Exchange
Act Registration") of the Offer to Purchase is incorporated herein by
reference.
 
ITEM 6. INTEREST IN SECURITIES OF THE SUBJECT COMPANY
 
  (a) and (b) The information set forth in the Introduction and Section 8
("Certain Information Concerning the Purchaser and the Parent") of, and
Schedule I ("Directors and Executive Officers of the Purchaser and the Parent")
to, the Offer to Purchase is incorporated herein by reference.
 
ITEM 7. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT
       TO THE SUBJECT COMPANY'S SECURITIES
 
  The information set forth in the Introduction, Section 8 ("Certain
Information Concerning the Purchaser and the Parent"), Section 10 ("Background
of the Offer; Contacts with the Company") and Section 11 ("Purpose of the
Offer; the Merger; Plans for the Company") of the Offer to Purchase is
incorporated herein by reference.
 
ITEM 8. PERSONS RETAINED, EMPLOYED OR TO BE COMPENSATED
 
  The information set forth in the Introduction and Section 16 ("Fees and
Expenses") of the Offer to Purchase is incorporated herein by reference.
 
ITEM 9. FINANCIAL STATEMENTS OF CERTAIN BIDDERS
 
  The information set forth in Section 8 ("Certain Information Concerning the
Purchaser and the Parent") of the Offer to Purchase is incorporated herein by
reference.
 
  The incorporation by reference herein of the above-referenced financial
information does not constitute an admission that such information is material
to a decision by a shareholder of the Company whether to sell, tender or hold
Shares (and associated Rights) being sought in the Offer.
 
ITEM 10. ADDITIONAL INFORMATION
 
  (a) None.
 
  (b) and (c) The information set forth in the Introduction, Section 2
("Acceptance for Payment and Payment for Shares and Rights") and Section 15
("Certain Legal Matters and Regulatory Approvals") of the Offer to Purchase is
incorporated herein by reference.
 
  (d) The information set forth in Section 13 ("Possible Effects of the Offer
on the Market for the Shares, NNM Quotation and Exchange Act Registration") and
Section 15 ("Certain Legal Matters and Regulatory Approvals") of the Offer to
Purchase is incorporated herein by reference.
 
  (e) The information set forth in the Introduction and Section 15 ("Certain
Legal Matters and Regulatory Approvals") of the Offer to Purchase is
incorporated herein by reference.
 
  (f) The information set forth in the Offer to Purchase and the Letter of
Transmittal is incorporated herein by reference.
 
                                       3
<PAGE>
 
ITEM 11. MATERIAL TO BE FILED AS EXHIBITS
 
  (a)(1) Offer to Purchase dated October 25, 1994.
 
  (a)(2) Letter of Transmittal.
 
  (a)(3) Notice of Guaranteed Delivery.
 
  (a)(4) Letter from the Dealer Manager to Brokers, Dealers, Commercial Banks,
         Trust Companies and Nominees.
 
  (a)(5) Letter to Clients for use by Brokers, Dealers, Commercial Banks, Trust
         Companies and Nominees.
 
  (a)(6) Guidelines for Certification of Taxpayer Identification Number on
         Substitute Form W-9.
 
  (a)(7) Summary Advertisement as published on October 25, 1994.
 
  (a)(8) Press Release issued by the Parent on October 24, 1994.
 
  (b)    Not applicable.
 
  (c)    Not applicable.
 
  (d)    Not applicable.
 
  (e)    Not applicable.
 
  (f)    Not applicable.
 
                                       4
<PAGE>
 
                                   SIGNATURE
 
  After due inquiry and to the best of my knowledge and belief, I certify that
the information set forth in this Statement is true, complete and correct.
 
                                          Thermo Electron Corporation
 
                                                 
                                          By:    /s/ George N. Hatsopoulos 
                                              ---------------------------------
                                              Name:  George N. Hatsopoulos
                                              Title: Chairman of the Board,
                                                     President and Chief
                                                     Executive Officer
 
                                          PB Acquisition Corp.
 
                                                  
                                          By:    /s/ John W. Wood, Jr. 
                                              ---------------------------------
                                              Name:  John W. Wood, Jr.
                                              Title: President
 
Date: October 25, 1994
 
                                       5
<PAGE>
 
                                 EXHIBIT INDEX
 
<TABLE>
<CAPTION>
 EXHIBIT  DESCRIPTION
 -------- -----------
 <C>      <S>
 11(a)(1) Offer to Purchase dated October 25, 1994
 11(a)(2) Letter of Transmittal
 11(a)(3) Notice of Guaranteed Delivery
 11(a)(4) Letter from the Dealer Manager to Brokers, Dealers, Commercial Banks,
          Trust Companies and Nominees
 11(a)(5) Letter to clients for use by Brokers, Dealers, Commercial Banks,
          Trust Companies and Nominees
 11(a)(6) Guidelines for Certification of Taxpayer Identification Number on
          Substitute Form W-9
 11(a)(7) Summary Advertisement as published on October 25, 1994
 11(a)(8) Press Release issued by the Parent on October 24, 1994
</TABLE>
 
                                       6

<PAGE>
 
                          OFFER TO PURCHASE FOR CASH
                    ALL OUTSTANDING SHARES OF COMMON STOCK
            (INCLUDING THE ASSOCIATED COMMON STOCK PURCHASE RIGHTS)
 
                                      OF
                          PURITAN-BENNETT CORPORATION
 
                                      AT
                             $24.50 NET PER SHARE
 
                                      BY
                             PB ACQUISITION CORP.
 
                         A WHOLLY OWNED SUBSIDIARY OF
                          THERMO ELECTRON CORPORATION

- --------------------------------------------------------------------------------
 THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK
    CITY TIME, ON TUESDAY, NOVEMBER 22, 1994, UNLESS THE OFFER IS EXTENDED.
 -------------------------------------------------------------------------------
 
  THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS: (1) THERE BEING VALIDLY
TENDERED AND NOT WITHDRAWN PRIOR TO THE EXPIRATION OF THE OFFER THAT NUMBER OF
SHARES WHICH, TOGETHER WITH THE SHARES BENEFICIALLY OWNED BY THE PURCHASER AND
THE PARENT, CONSTITUTES AT LEAST A MAJORITY OF THE SHARES OUTSTANDING
(DETERMINED ON A FULLY DILUTED BASIS); (2) THE COMPANY'S COMMON STOCK PURCHASE
RIGHTS HAVING BEEN REDEEMED, OR MADE INAPPLICABLE TO THE OFFER AND THE
PROPOSED MERGER DESCRIBED HEREIN, BY THE COMPANY'S BOARD OF DIRECTORS; (3) THE
PURCHASER BEING SATISFIED, IN ITS SOLE DISCRETION, THAT SECTION 203 OF THE
DELAWARE GENERAL CORPORATION LAW IS INAPPLICABLE TO THE PROPOSED MERGER
DESCRIBED HEREIN; AND (4) THE PURCHASER BEING SATISFIED, IN ITS SOLE
DISCRETION, THAT THE SUPERMAJORITY VOTING REQUIREMENT CONTAINED IN ARTICLE
FIFTH OF THE COMPANY'S ARTICLES OF INCORPORATION IS INAPPLICABLE TO THE
PROPOSED MERGER DESCRIBED HEREIN. SATISFACTION OF ONE OR MORE OF THE FOREGOING
CONDITIONS WILL REQUIRE THE APPROVAL OF THE OFFER AND THE PROPOSED MERGER
DESCRIBED HEREIN BY THE BOARD OF DIRECTORS OF THE COMPANY. THE OFFER IS ALSO
SUBJECT TO CERTAIN OTHER TERMS AND CONDITIONS CONTAINED IN THIS OFFER TO
PURCHASE. SEE THE INTRODUCTION AND SECTIONS 1 AND 14.
 
  THE OFFER IS NOT CONDITIONED UPON THE PURCHASER OBTAINING FINANCING.
                               ---------------
 
                                   IMPORTANT
 
  Any shareholder desiring to tender all or any portion of such shareholder's
shares of Common Stock, $1.00 par value per share (the "Shares"), and the
associated Common Stock Purchase Rights (the "Rights"), of the Company should
either (1) complete and sign the enclosed Letter of Transmittal (or a
facsimile thereof) in accordance with the instructions in the Letter of
Transmittal, have such shareholder's signature thereon guaranteed if required
by Instruction 1 of the Letter of Transmittal, mail or deliver the Letter of
Transmittal (or such facsimile) and any other required documents to the
Depositary (as defined herein), and either deliver the certificates
representing the tendered Shares and, if separate, the certificates
representing the associated Rights and any other required documents to the
Depositary or tender such Shares (and Rights, if applicable) pursuant to the
procedure for book-entry transfer set forth in Section 3 of this Offer to
Purchase or (2) request such shareholder's broker, dealer, commercial bank,
trust company or other nominee to effect the transaction for such shareholder.
 
  Shareholders having Shares (and Rights, if applicable) registered in the
name of a broker, dealer, commercial bank, trust company or other nominee must
contact such broker, dealer, commercial bank, trust company or other nominee
if they desire to tender Shares (and Rights, if applicable) so registered.
Unless, on or before the Expiration Date, the Rights have been redeemed by the
Company's Board of Directors, holders of Shares will be required to tender one
Right for each Share tendered in order to effect a valid tender of such Share.
 
  A shareholder who desires to tender Shares (and Rights, if applicable) and
whose certificates representing such Shares (and Rights, if applicable) are
not immediately available, or who cannot comply with the procedure for book-
entry transfer on a timely basis, may tender such Shares (and Rights, if
applicable) by following the procedures for guaranteed delivery set forth in
Section 3.
 
  Questions and requests for assistance may be directed to Lehman Brothers
Inc. (the "Dealer Manager") or to D.F. King & Co., Inc. (the "Information
Agent"), at their respective addresses and telephone numbers set forth on the
back cover of this Offer to Purchase. Additional copies of this Offer to
Purchase, the Letter of Transmittal and all other tender offer materials may
also be obtained from the Information Agent or from brokers, dealers,
commercial banks or trust companies.
 
                               ---------------
                     The Dealer Manager for the Offer is:

                                LEHMAN BROTHERS
October 25, 1994
<PAGE>
 
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                                                            PAGE
                                                                            ----
<S>                                                                         <C>
INTRODUCTION..............................................................    1
THE TENDER OFFER..........................................................    5
   1. Terms of the Offer; Expiration Date.................................    5
   2. Acceptance for Payment and Payment for Shares and Rights............    6
   3. Procedure for Tendering Shares and Rights...........................    8
   4. Withdrawal Rights...................................................   11
   5. Certain Federal Income Tax Consequences.............................   12
   6. Price Range of Shares; Dividends....................................   12
   7. Certain Information Concerning the Company..........................   13
   8. Certain Information Concerning the Purchaser and the Parent.........   14
   9. Source and Amount of Funds..........................................   16
  10. Background of the Offer; Contacts with the Company..................   16
  11. Purpose of the Offer; the Merger; Plans for the Company.............   21
  12. Dividends and Distributions.........................................   28
  13. Possible Effects of the Offer on the Market for the Shares,
      NNM Quotation and Exchange Act Registration.........................   29
  14. Certain Conditions of the Offer.....................................   30
  15. Certain Legal Matters and Regulatory Approvals......................   34
  16. Fees and Expenses...................................................   37
  17. Miscellaneous.......................................................   37
Schedule I--Directors and Executive Officers of the Purchaser and the Par-
 ent......................................................................  I-1
</TABLE>
<PAGE>
 
To the Holders of Common Stock 
 (including the associated Common 
 Stock Purchase Rights) of 
 PURITAN-BENNETT CORPORATION
 
                                  INTRODUCTION
 
  PB Acquisition Corp., a Delaware corporation (the "Purchaser") and a wholly
owned subsidiary of Thermo Electron Corporation, a Delaware corporation (the
"Parent"), hereby offers to purchase all of the outstanding shares of Common
Stock, $1.00 par value per share (the "Shares"), of Puritan-Bennett
Corporation, a Delaware corporation (the "Company"), and (unless, on or before
the Expiration Date (as defined below), the associated Common Stock Purchase
Rights (the "Rights") have been redeemed by the Company's Board of Directors)
the Rights issued pursuant to the Rights Agreement, dated as of May 2, 1989
(the "Rights Agreement"), between the Company and United Missouri Bank of
Kansas City, N.A., as Rights Agent (the "Rights Agent"), at a purchase price of
$24.50 per Share (and associated Right), net to the seller in cash, without
interest thereon, upon the terms and subject to the conditions set forth in
this Offer to Purchase and in the related Letter of Transmittal (which together
constitute the "Offer"). Unless the context requires otherwise, all references
in this Offer to Purchase to "Shares" shall be deemed to refer also to the
Rights, and all references to "Rights" shall be deemed to include all benefits
that may inure to the shareholders of the Company or to holders of the Rights
pursuant to the Rights Agreement.
 
  Tendering shareholders will not be obligated to pay brokerage fees or
commissions or, subject to Instruction 6 of the Letter of Transmittal, stock
transfer taxes on the transfer and sale of Shares and Rights to the Purchaser
pursuant to the Offer. The Purchaser will pay all fees and expenses of Lehman
Brothers Inc., which is acting as Dealer Manager for the Offer (in such
capacity, "Lehman Brothers" or the "Dealer Manager"), The First National Bank
of Boston (the "Depositary") and D.F. King & Co., Inc. (the "Information
Agent") incurred in connection with the Offer. See Section 16.
 
  The purpose of the Offer and the Merger (as defined below) is to acquire
control of, and the entire equity interest in, the Company. The Offer, as the
first step in the acquisition of the Company, is intended to facilitate the
acquisition of all outstanding Shares. As soon as practicable following
consummation of the Offer, the Purchaser intends to seek the maximum
representation obtainable on the Company's Board of Directors and to propose,
and to seek to have the Company consummate as soon as practicable after
consummation of the Offer, a merger or similar business combination with the
Purchaser or another direct or indirect wholly owned subsidiary of the Parent
(the "Merger"), pursuant to which each then outstanding Share (other than (1)
Shares held by the Parent, the Purchaser or any other direct or indirect wholly
owned subsidiary of the Parent, (2) Shares held in the treasury of the Company
and (3) Shares held by shareholders who properly exercise appraisal rights
under Section 262 of the Delaware General Corporation Law (the "DGCL")) would
be converted into the right to receive in cash the same price per Share paid by
the Purchaser in the Offer.
 
  Although the Purchaser intends to seek to have the Company consummate the
Merger as soon as practicable after consummation of the Offer, if the Board of
Directors of the Company opposes the Offer and the Merger, certain provisions
of the Rights, the DGCL, the Company's Articles of Incorporation (the
"Articles") and the Company's By-Laws (the "By-Laws") will affect the ability
of the Purchaser to obtain control of the Company and to effect the Merger.
Accordingly, the timing and details of the Merger will depend on a variety of
factors and legal requirements, the actions of the Board of Directors of the
Company, the number of Shares acquired by the Purchaser pursuant to the Offer,
and whether the Minimum Condition, the Rights Condition, the Section 203
Condition and/or the Supermajority Voting Condition (each as defined below) is
satisfied or waived. Satisfaction of one or more of the foregoing conditions
will require the approval of the Offer and the Merger by the Board of Directors
of the Company. Upon consummation of the Offer, assuming the Minimum Condition,
the Rights Condition, the Section 203 Condition and the Supermajority Voting
Condition, and the other conditions to the Offer set forth in Section 14, are
satisfied, the Parent and the Purchaser will own sufficient Shares, subject to
the procedures described in Section 11, ultimately to elect
<PAGE>
 
the members of the Company's Board of Directors and to approve the Merger
without the affirmative vote of any other shareholder of the Company. For a
discussion of certain appraisal rights available to shareholders upon
consummation of the Merger, see Section 11.
 
  The Parent has requested the opportunity to meet with the Company on several
occasions in order to negotiate a merger agreement with the Company. Although
the Company has sent a letter to the Parent requesting additional information
concerning the Parent's merger proposal, the Company has refused to meet in
person with the Parent to negotiate a merger agreement. As a result, the
Parent determined to commence the Offer. See Section 10. The Parent intends to
continue to seek to meet with the Company in order to negotiate a merger
agreement. However, there can be no assurance that the Company will agree to
meet with the Parent for such purpose or, if such negotiations do commence, as
to the outcome thereof. The Parent and the Purchaser reserve the right to
amend or terminate the Offer if the Company should agree to enter into a
merger agreement with the Parent and the Purchaser. The Parent believes that
the Offer provides the Company's shareholders with a method of expressing to
the Board of Directors of the Company that they wish to be able to accept the
Offer and to approve the Merger or a similar transaction with the Parent and
the Purchaser.
 
  THE OFFER IS CONDITIONED, AMONG OTHER THINGS, UPON SATISFACTION, IN THE
PURCHASER'S SOLE DISCRETION, OF THE FOLLOWING CONDITIONS: (1) THE MINIMUM
CONDITION, (2) THE RIGHTS CONDITION, (3) THE SECTION 203 CONDITION AND (4) THE
SUPERMAJORITY VOTING CONDITION, EACH OF WHICH IS DESCRIBED BELOW. SATISFACTION
OF ONE OR MORE OF THE FOREGOING CONDITIONS WILL REQUIRE THE APPROVAL OF THE
OFFER AND THE MERGER BY THE BOARD OF DIRECTORS OF THE COMPANY. CERTAIN OTHER
CONDITIONS TO THE OFFER ARE DESCRIBED IN SECTION 14.
 
  The Minimum Condition. The Offer is subject to the condition (the "Minimum
Condition") that there shall have been validly tendered and not withdrawn on
or prior to the Expiration Date (as defined below) that number of Shares
which, together with the Shares beneficially owned by the Purchaser and the
Parent, constitutes at least a majority of the Shares outstanding (determined
on a fully diluted basis).
 
  According to the Company's Quarterly Report on Form 10-Q for the quarter
ended July 31, 1994 (the "July 1994 Form 10-Q"), at September 7, 1994,
12,524,965 Shares were outstanding. According to the Company's Annual Report
on Form 10-K for the fiscal year ended January 31, 1994 (the "1994 Form 10-
K"), at January 31, 1994, options covering a total of 957,969 Shares were
outstanding under the Company's various stock option plans (collectively, the
"Company Option Plans"). The Parent currently beneficially owns an aggregate
of 610,000 Shares, representing approximately 4.9% of the Shares outstanding
(approximately 4.5% on a fully diluted basis), based on the number of Shares
outstanding at September 7, 1994 and the number of options outstanding at
January 31, 1994. See Section 8. Based on this information and assuming
exercise of all options outstanding under the Company Option Plans as of
January 31, 1994, the Purchaser believes that the total number of shares
outstanding (on a fully diluted basis) is 13,482,934, and, therefore, that the
Minimum Condition will be satisfied if approximately 6,131,468 Shares are
validly tendered pursuant to the Offer and not withdrawn.
 
  The Rights Condition. The Offer is subject to the condition (the "Rights
Condition") that the Rights shall have been redeemed, or made inapplicable to
the Offer and the Merger, by the Company's Board of Directors.
 
  The Rights are described in the Company's Registration Statement on Form 8-A
filed with the Securities and Exchange Commission (the "Commission") on May
15, 1989 (the "Form 8-A"). A summary of the Rights is contained in Section 11.
The Purchaser believes that the consummation of the Offer likely would trigger
certain provisions of the Rights and, as a result, cause significant dilution
to the Purchaser's interest in the Company and render the Offer and the Merger
economically unattractive to the Purchaser.
 
  According to the Company's filings with the Commission, at any time until a
person becomes an Acquiring Person (as defined in Section 11), the Company may
redeem the Rights in whole, but not in part,
 
                                       2
<PAGE>
 
at a price of $.01 per Right, subject to adjustment. According to such filings,
until the Distribution Date (as defined in Section 11), the Rights will be
represented by and transferred with and only with the Shares and the surrender
for transfer of any of the certificates representing Shares (the "Share
Certificates") will also constitute the surrender for transfer of the Rights
associated with the Shares represented by such Share Certificates. According to
such filings, as soon as practicable following the Distribution Date, separate
certificates representing the Rights ("Rights Certificates") will be mailed to
holders of record of Shares as of the close of business on the Distribution
Date. After the Distribution Date, such separate Rights Certificates alone will
represent the Rights.
 
  Based on publicly available information, the Purchaser believes that, as of
October 24, 1994, the Rights were not exercisable, Rights Certificates had not
been issued and the Rights were represented by the Share Certificates. The
Purchaser believes that, under the Rights Agreement, as a result of the
commencement of the Offer, the Distribution Date will be as early as November
3, 1994, unless prior to such date the Company's Board of Directors redeems the
Rights or takes action to delay the Distribution Date.
 
  Unless, on or before the Expiration Date, the Rights have been redeemed by
the Company's Board of Directors, holders of Shares will be required to tender
one Right for each Share tendered in order to effect a valid tender of such
Share. If separate certificates for the Rights are not issued, a tender of
Shares will also constitute a tender of associated Rights.
 
  The Purchaser believes that, under the circumstances of the Offer and under
applicable law, the Board of Directors of the Company is obligated by its
fiduciary responsibilities to redeem the Rights or to approve the Offer and
determine that the Offer is adequate and in the best interests of the Company
and its shareholders (following which approval and determination the key
unfavorable provisions of the Rights would be inapplicable to the Offer and the
Merger) in order to permit the Offer and the Merger to be consummated. However,
there can be no assurance that the Company's Board of Directors will do so. The
Purchaser is hereby requesting that the Company's Board of Directors redeem the
Rights or approve the Offer and make such determination.
 
  The Section 203 Condition. The Offer is subject to the condition (the
"Section 203 Condition") that the Purchaser shall be satisfied, in its sole
discretion, that the restrictions on business combinations contained in Section
203 ("Section 203") of the DGCL are inapplicable to the Merger.
 
  In general, Section 203 prevents an "Interested Stockholder" (defined
generally as any person that directly or indirectly beneficially owns 15% or
more of a corporation's outstanding voting stock), or any affiliate of an
Interested Stockholder, from engaging in a "Business Combination" (defined to
include a variety of transactions, including mergers) with a Delaware
corporation for three years following the date that such person became an
Interested Stockholder, unless (1) prior to the date such person became an
Interested Stockholder, the board of directors of the corporation approved
either the Business Combination or the transaction which resulted in the person
becoming an Interested Stockholder, (2) upon consummation of the transaction
which resulted in the person becoming an Interested Stockholder, the Interested
Stockholder owned at least 85% of the voting stock of the corporation
outstanding at the time the transaction commenced (excluding stock held by
directors who are also officers of the corporation and by employee stock plans
in which employee participants do not have the right to determine
confidentially whether shares held subject to the plan will be tendered in a
tender or exchange offer) or (3) on or subsequent to the date the Interested
Stockholder became such, the Business Combination is (a) approved by the board
of directors of the corporation and (b) authorized at an annual or special
meeting of shareholders, and not by written consent, by the affirmative vote of
the holders of at least 66 2/3% of the outstanding voting stock of the
corporation which is not owned by the Interested Stockholder.
 
  Consequently, under Section 203, unless the Board of Directors of the Company
approves the Offer and the Merger in advance of the consummation of the Offer
or, upon completion of the Offer, the Purchaser owns at least 85% of the
Shares, the Merger could not occur for three years unless it is approved by a
two-thirds vote of the Shares not owned by the Parent, the Purchaser or their
affiliates. This requirement
 
                                       3
<PAGE>
 
fundamentally interferes with the practical ability of the Purchaser to acquire
Shares in light of the financial and operational burdens that would be placed
on the Parent and the Purchaser if they were to consummate the Offer, but were
unable to consummate the Merger. A more detailed description of Section 203 is
contained in Section 11.
 
  The Purchaser believes that, under the circumstances of the Offer and under
applicable law, the Board of Directors of the Company is obligated by its
fiduciary responsibilities to approve, pursuant to Section 203, the acquisition
of Shares pursuant to the Offer and the Merger. However, there can be no
assurance that the Company's Board of Directors will do so. The Purchaser is
hereby requesting that the Company's Board of Directors approve the Offer and
the Merger for purposes of Section 203.
 
  The Supermajority Voting Condition. The Offer is subject to the condition
(the "Supermajority Voting Condition") that the Purchaser shall be satisfied,
in its sole discretion, that the 66 2/3% Charter Provision (as defined below)
of Article Fifth of the Articles is inapplicable to the proposed Merger.
 
  Article Fifth of the Articles provides that, in addition to any affirmative
vote required by applicable law (currently, the affirmative vote of holders of
at least a majority of the outstanding Shares), the affirmative vote of the
holders of not less than 66 2/3% of the voting power of all issued and
outstanding shares of voting stock of the Company (voting as a single class) is
required to approve certain business combinations (including mergers) between
the Company and a person who or which owns of record or beneficially, directly
or indirectly, or is otherwise entitled to vote shares constituting 5% or more
of the total votes which may be cast with respect to the matter (a "5%
Stockholder"), unless the business combination is approved and recommended to
the shareholders of the Company by the favorable vote of at least 66 2/3% of
the whole Board of Directors of the Company (the "66 2/3% Charter Provision").
The acquisition of in excess of 5% of the outstanding Shares by the Purchaser
as a result of the Offer would make the Purchaser a 5% Stockholder for purposes
of the 66 2/3% Charter Provision.
 
  The Purchaser believes that, under the circumstances of the Offer and under
applicable law, the Board of Directors of the Company is obligated by its
fiduciary responsibilities to approve and recommend the Merger to the
shareholders of the Company in order to permit the Offer and the Merger to be
consummated. However, there can be no assurance that the Company's Board of
Directors will do so. The Purchaser is hereby requesting that the Company's
Board of Directors approve and recommend the Merger to the shareholders of the
Company in order to make the 66 2/3% Charter Provision inapplicable to the
Merger.
 
                                     * * *
 
  The Purchaser expressly reserves the right to waive any one or more of the
conditions to the Offer. See Sections 11, 14 and 15.
 
  In the event that the Offer is not consummated, the Purchaser intends to
explore all options which may be available to it at such time, which may
include, without limitation, the acquisition of Shares through open market
purchases, privately negotiated transactions, a tender offer or exchange offer
or otherwise, upon such terms and at such prices as it shall determine, which
may be more or less than the price to be paid pursuant to the Offer. The
Purchaser also reserves the right to dispose of Shares.
 
  THIS OFFER TO PURCHASE AND THE RELATED LETTER OF TRANSMITTAL CONTAIN
IMPORTANT INFORMATION WHICH SHOULD BE READ BEFORE ANY DECISION IS MADE WITH
RESPECT TO THE OFFER.
 
 
                                       4
<PAGE>
 
                                THE TENDER OFFER
 
  1. TERMS OF THE OFFER; EXPIRATION DATE. Upon the terms and subject to the
conditions of the Offer (including, if the Offer is extended or amended, the
terms and conditions of any such extension or amendment), the Purchaser will
accept for payment and pay for all Shares validly tendered on or prior to the
Expiration Date and not properly withdrawn as permitted by Section 4. The term
"Expiration Date" means 12:00 midnight, New York City time, on Tuesday,
November 22, 1994, unless and until the Purchaser, in its sole discretion,
shall have extended the period during which the Offer is open, in which event
the term "Expiration Date" shall mean the latest time and date at which the
Offer, as so extended by the Purchaser, shall expire.
 
  THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, SATISFACTION OF EACH OF
THE CONDITIONS SET FORTH ABOVE IN THE INTRODUCTION AND IN SECTION 14. THE
PURCHASER RESERVES THE RIGHT (BUT SHALL NOT BE OBLIGATED) TO WAIVE ANY OR ALL
OF SUCH CONDITIONS.
 
  If by the Expiration Date, any or all of such conditions have not been
satisfied or waived, the Purchaser reserves the right (but shall not be
obligated) (i) to decline to purchase any of the Shares tendered and terminate
the Offer, (ii) to waive all of the unsatisfied conditions and, subject to
complying with applicable rules and regulations of the Commission, to purchase
all Shares validly tendered or (iii) to extend the Offer and, subject to the
right of shareholders to withdraw Shares until the Expiration Date, retain the
Shares which have been tendered during the period or periods for which the
Offer is extended.
 
  The Purchaser expressly reserves the right, in its sole discretion, at any
time and from time to time, to extend the period during which the Offer is open
for any reason, including the occurrence of any of the conditions specified in
Section 14, and thereby delay acceptance for payment of, or payment for, any
Shares, by giving oral or written notice of such extension to the Depositary.
During any such extension, all Shares previously tendered and not properly
withdrawn will remain subject to the Offer, subject to the rights of a
tendering shareholder to withdraw such shareholder's Shares. See Section 4.
 
  Subject to the applicable regulations of the Commission, the Purchaser also
reserves the right, in its sole discretion, at any time or from time to time to
(i) delay acceptance for payment of or, regardless of whether such Shares were
theretofore accepted for payment, payment for any Shares pending receipt of any
regulatory approvals specified in Section 15, (ii) terminate the Offer (whether
or not any Shares have theretofore been accepted for payment) if any of the
conditions referred to in Section 14 has not been satisfied or upon the
occurrence of any of the events specified in Section 14 and (iii) waive any
condition or otherwise amend the Offer in any respect, in each case, by giving
oral or written notice of such delay, termination, waiver or amendment to the
Depositary and by making a public announcement thereof. The Purchaser
acknowledges (i) that Rule 14e-1(c) under the Exchange Act requires the
Purchaser to pay the consideration offered or return the Shares tendered
promptly after the termination or withdrawal of the Offer and (ii) that the
Purchaser may not delay acceptance for payment of, or payment for (except as
provided in clause (i) of the preceding sentence), any Shares upon the
occurrence of any of the conditions specified in Section 14 without extending
the period of time during which the Offer is open.
 
  The rights reserved by the Purchaser above are in addition to the Purchaser's
rights pursuant to Section 14. Any extension, delay, termination, waiver or
amendment will be followed as promptly as practicable by public announcement
thereof, and such announcement, in the case of an extension, will be made no
later than 9:00 a.m., New York City time, on the next business day after the
previously scheduled Expiration Date. Without limiting the manner in which the
Purchaser may choose to make any public announcement, except as provided by
applicable law (including Rules 14d-4(c) and 14d-6(d) under the Exchange Act,
which require that material changes be promptly disseminated to holders of
Shares), the Purchaser shall have no obligation to publish, advertise or
otherwise communicate any such public announcement other than by issuing a
release to the Dow Jones News Service.
 
                                       5
<PAGE>
 
  If the Purchaser makes a material change in the terms of the Offer, or if it
waives a material condition of the Offer, the Purchaser will disseminate
additional tender offer materials (including by public announcement as set
forth above) and extend the Offer to the extent required by Rules 14d-4(c) and
14d-6(d) under the Exchange Act. The minimum period during which an offer must
remain open following material changes in the terms of the offer, other than a
change in price or a change in the percentage of securities sought or a change
in any dealer's soliciting fee, will depend upon the facts and circumstances,
including the materiality, of the changes. With respect to a change in price
or, subject to certain limitations, a change in the percentage of securities
sought or a change in any dealer's soliciting fee, a minimum ten business day
period from the day of such change is generally required to allow for adequate
dissemination to shareholders. Accordingly, if, prior to the Expiration Date,
the Purchaser decreases the number of Shares being sought, increases or
decreases the consideration offered pursuant to the Offer or adds a dealer's
soliciting fee, and if the Offer is scheduled to expire at any time earlier
than the period ending on the tenth business day from the date that notice of
such increase, decrease or addition is first published, sent or given to
shareholders, the Offer will be extended at least until the expiration of such
ten business day period. For purposes of the Offer, a "business day" means any
day other than a Saturday, Sunday or a federal holiday and consists of the
time period from 12:01 a.m. through 12:00 midnight, New York City time.
 
  A request pursuant to Rule 14d-5 under the Exchange Act is being made to the
Company for the use of its shareholder list, list of the holders of Rights, if
any, and security position listings for the purpose of disseminating the Offer
to holders of Shares. Upon compliance by the Company with such request, this
Offer to Purchase and the related Letter of Transmittal and, if required,
other relevant materials will be mailed to record holders of Shares and Rights
whose names appear on the Company's shareholder list and list of holders of
Rights, if applicable, and will be furnished to brokers, dealers, commercial
banks, trust companies and similar persons whose names, or the names of whose
nominees, appear on the shareholder list and list of holders of Rights, if
applicable, or who are listed as participants in a clearing agency's security
position listing for subsequent transmittal to beneficial owners of Shares.
 
  2. ACCEPTANCE FOR PAYMENT AND PAYMENT FOR SHARES AND RIGHTS. Upon the terms
and subject to the conditions of the Offer (including, if the Offer is
extended or amended, the terms and conditions of any such extension or
amendment), the Purchaser will accept for payment, and will pay for, Shares
validly tendered prior to the Expiration Date and not properly withdrawn in
accordance with Section 3 (including Shares validly tendered and not withdrawn
during any extension of the Offer, if the Offer is extended, subject to the
terms and conditions of such extension) as soon as practicable after the last
to occur of (i) the Expiration Date and (ii) the expiration or termination of
the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of
1976, as amended (the "HSR Act") in connection with the filings to be made
related to the Offer. In addition, the Purchaser expressly reserves the right,
in its sole discretion, to delay the acceptance for payment of, or payment
for, Shares in order to comply, in whole or in part, with any other applicable
law. Any such delays will be effected in compliance with Rule 14e-1 under the
Exchange Act. Any determination concerning the satisfaction of such terms and
conditions shall be within the sole discretion of the Purchaser and such
determination shall be final and binding on all tendering shareholders. See
Section 14.
 
  In all cases, payment for Shares tendered and accepted for payment pursuant
to the Offer will be made only after timely receipt by the Depositary of (i)
Share Certificates and, if applicable, Rights Certificates, or timely
confirmation (a "Book-Entry Confirmation") of a book-entry transfer of such
Shares and Rights, if applicable, into the Depositary's account at The
Depository Trust Company, the Midwest Securities Trust Company or the
Philadelphia Depository Trust Company (each a "Book-Entry Transfer Facility"
and, collectively, the "Book-Entry Transfer Facilities") pursuant to the
procedures set forth in Section 3, (ii) the Letter of Transmittal (or a
facsimile thereof), properly completed and duly executed, with any required
signature guarantees, or an Agent's Message (as defined below) in connection
with a book-entry transfer, and (iii) any other documents required by the
Letter of Transmittal.
 
  The term "Agent's Message" means a message, transmitted by a Book-Entry
Transfer Facility to, and received by, the Depositary and forming a part of a
Book-Entry Confirmation, which states that such Book-
 
                                       6
<PAGE>
 
Entry Transfer Facility has received an express acknowledgment from the
participant in such Book-Entry Transfer Facility tendering the Shares and, if
applicable, the Rights which are the subject of such Book-Entry Confirmation,
that such participant has received and agrees to be bound by the terms of the
Letter of Transmittal and that the Purchaser may enforce such agreement against
such participant.
 
  Unless, on or before the Expiration Date, the Rights have been redeemed by
the Company's Board of Directors, if Rights Certificates have been distributed
to holders of Shares, such holders are required to tender Rights Certificate(s)
representing a number of Rights equal to the number of Shares being tendered in
order to effect a valid tender of such Shares.
 
  The Parent intends to file on the date hereof with the Federal Trade
Commission (the "FTC") and the Antitrust Division of the Department of Justice
(the "Antitrust Division") a Premerger Notification and Report Form under the
HSR Act with respect to the Offer. Accordingly, it is anticipated that the
waiting period under the HSR Act applicable to the Offer will expire at 11:59
p.m., New York City time, on Wednesday, November 9, 1994. However, prior to the
expiration or termination of the waiting period, the FTC or the Antitrust
Division may extend the waiting period applicable to the Offer by requesting
additional information from the Parent. If such a request is made, the waiting
period applicable to the Offer will expire on the tenth calendar day after the
date of substantial compliance by the Parent with such request. Thereafter, the
waiting period may only be extended by court order or with the agreement of the
Parent. The waiting period under the HSR Act may be terminated by the FTC and
the Antitrust Division prior to its expiration. The Parent has requested early
termination of the waiting period applicable to the Offer, although there can
be no assurance that this request will be granted. See Section 15 for
additional information regarding the HSR Act and other potentially applicable
regulatory provisions.
 
  For purposes of the Offer, the Purchaser will be deemed to have accepted for
payment (and thereby purchased) Shares validly tendered and not properly
withdrawn as, if and when the Purchaser gives oral or written notice to the
Depositary of the Purchaser's acceptance for payment of such Shares pursuant to
the Offer. Upon the terms and subject to the conditions of the Offer, payment
for Shares so accepted for payment pursuant to the Offer will be made by
deposit of the aggregate purchase price therefor with the Depositary, which
will act as agent for tendering shareholders for the purpose of receiving
payment from the Purchaser and transmitting such payment to shareholders whose
Shares have been accepted for payment. UNDER NO CIRCUMSTANCES WILL INTEREST ON
THE PURCHASE PRICE FOR SHARES BE PAID BY THE PURCHASER, REGARDLESS OF ANY DELAY
IN MAKING SUCH PAYMENT. Upon the deposit of funds with the Depository for the
purpose of making payment to validly tendering shareholders, the Purchaser's
obligation to make such payment shall be satisfied and such tendering
shareholders must thereafter look solely to the Depository for payment of the
amounts owed to them by reason of the acceptance for payment of Shares pursuant
to the Offer.
 
  If any tendered Shares are not accepted for payment for any reason or if
Share Certificates are submitted for more Shares than are tendered, Share
Certificates representing unpurchased or untendered Shares will be returned,
without expense to the tendering shareholder (or, in the case of Shares
tendered by book-entry transfer into the Depositary's account at a Book-Entry
Transfer Facility pursuant to the procedures set forth in Section 3, such
Shares will be credited to an account maintained at such Book-Entry Transfer
Facility), in each case with the related Rights Certificates, if any, as
promptly as practicable following the expiration, termination or withdrawal of
the Offer.
 
  If, prior to the Expiration Date, the Purchaser increases the consideration
offered to shareholders pursuant to the Offer, such increased consideration
will be paid to all shareholders whose Shares are purchased pursuant to the
Offer, whether or not such Shares were tendered or accepted for payment prior
to such increase in consideration.
 
  The Purchaser reserves the right to transfer or assign, in whole or from time
to time in part, to one or more of its affiliates, the right to purchase all or
any portion of the Shares tendered pursuant to the Offer, but any such transfer
or assignment will not relieve the Purchaser of its obligations under the Offer
and will in
 
                                       7
<PAGE>
 
no way prejudice the rights of tendering shareholders to receive payment for
Shares validly tendered and accepted for payment pursuant to the Offer.
 
  3. PROCEDURE FOR TENDERING SHARES AND RIGHTS. Except as set forth below, in
order for Shares to be validly tendered pursuant to the Offer, the Letter of
Transmittal (or a facsimile thereof), properly completed and duly executed,
together with any required signature guarantees, or an Agent's Message in
connection with a book-entry delivery of Shares and Rights, and any other
documents required by the Letter of Transmittal, must be received by the
Depositary at one of its addresses set forth on the back cover of this Offer to
Purchase on or prior to the Expiration Date and either (i) Share Certificates
and Rights Certificates, if applicable, representing tendered Shares and Rights
must be received by the Depositary at such address or such Shares and Rights
must be tendered pursuant to the procedure for book-entry transfer described
below and a Book-Entry Confirmation must be received by the Depositary, in each
case on or prior to the Expiration Date, or (ii) the guaranteed delivery
procedures described below must be complied with.
 
  Rights Certificates. Unless, on or before the Expiration Date, the Rights
have been redeemed by the Company's Board of Directors, holders of Shares will
be required to tender one Right for each Share tendered in order to effect a
valid tender of such Share. Accordingly, shareholders who sell their Rights
separately from their Shares and do not otherwise acquire Rights may not be
able to satisfy the requirements of the Offer for a valid tender of Shares.
 
  If separate certificates for the Rights are not issued, a tender of Shares
will also constitute a tender of the associated Rights. If the Distribution
Date has occurred and Rights Certificates have been distributed to holders of
Shares prior to the date of tender pursuant to the Offer, in order for Rights
(and the corresponding Shares) to be validly tendered, Rights Certificates
representing a number of Rights equal to the number of Shares being tendered
must be delivered to the Depositary or, if available, a Book-Entry Confirmation
must be received by the Depositary with respect thereto. If the Distribution
Date has occurred and Rights Certificates have not been distributed prior to
the time Shares are tendered pursuant to the Offer, Rights may be tendered
prior to a shareholder receiving Rights Certificates by use of the guaranteed
delivery procedures described below. In any case, a tender of Shares without
Rights Certificates constitutes an agreement by the tendering shareholder to
deliver Rights Certificates representing a number of Rights equal to the number
of Shares tendered pursuant to the Offer to the Depositary within five business
days after the date such Rights Certificates are distributed. Unless, on or
before the Expiration Date, the Rights have been redeemed by the Company's
Board of Directors, the Purchaser reserves the right to require that the
Depositary receive such Rights Certificates, or Book-Entry Confirmation, if
available, with respect to such Rights, prior to accepting the related Shares
for payment. In that event, payment for Shares tendered and accepted for
payment pursuant to the Offer will be made only after timely receipt by the
Depositary of, among other things, Rights Certificates, or Book-Entry
Confirmation, if available, with respect to such Rights, if Rights Certificates
have been distributed to holders of Shares. See Section 2.
 
  THE METHOD OF DELIVERY OF SHARE CERTIFICATES OR OF RIGHTS CERTIFICATES, IF
APPLICABLE, AND ALL OTHER REQUIRED DOCUMENTS, INCLUDING DELIVERY THROUGH ANY
BOOK-ENTRY TRANSFER FACILITY, IS AT THE OPTION AND SOLE RISK OF THE TENDERING
SHAREHOLDER AND THE DELIVERY WILL BE DEEMED MADE ONLY WHEN ACTUALLY RECEIVED BY
THE DEPOSITARY. IF DELIVERY IS BY MAIL, REGISTERED MAIL WITH RETURN RECEIPT
REQUESTED, PROPERLY INSURED, IS RECOMMENDED. IN ALL CASES, SUFFICIENT TIME
SHOULD BE ALLOWED TO ENSURE TIMELY DELIVERY.
 
  Book-Entry Transfer. The Depositary will make a request to establish accounts
with respect to the Shares at the Book-Entry Transfer Facilities for purposes
of the Offer within two business days after the date of this Offer to Purchase.
Any financial institution that is a participant in the system of any Book-Entry
Transfer Facility may make book-entry delivery of Shares by causing such Book-
Entry Transfer Facility to transfer such Shares into the Depositary's account
at such Book-Entry Transfer Facility in accordance with such Book-Entry
Transfer Facility's procedures for such transfer. However, although delivery of
Shares may be effected through book-entry transfer at a Book-Entry Transfer
Facility, the Letter of Transmittal (or a facsimile thereof), properly
completed and duly executed, together with any required signature guarantees,
 
                                       8
<PAGE>
 
or an Agent's Message in connection with a book-entry transfer, and any other
documents required by the Letter of Transmittal, must, in any case, be received
by the Depositary at one of its addresses set forth on the back cover of this
Offer to Purchase on or prior to the Expiration Date, or the guaranteed
delivery procedures described below must be complied with.
 
  If the Distribution Date occurs, to the extent that the Rights become
eligible for book-entry transfer under procedures established by a particular
Book-Entry Transfer Facility, the Depositary will make a request to establish
an account with respect to the Rights at such Book-Entry Transfer Facility as
soon as practicable. No assurance can be given, however, that book-entry
delivery of Rights will be available. If book-entry delivery of Rights is
available, the foregoing book-entry transfer procedure will also apply to
Rights. If book-entry delivery is not available and if separate Rights
Certificates have been issued, a tendering shareholder is not relieved of
delivery requirements hereunder and thus will be required to tender Rights by
means of actual physical delivery of Rights Certificates or pursuant to the
guaranteed delivery procedures set forth below.
 
  DELIVERY OF DOCUMENTS TO A BOOK-ENTRY TRANSFER FACILITY DOES NOT CONSTITUTE
DELIVERY TO THE DEPOSITARY.
 
  Signature Guarantees. Signatures on Letters of Transmittal must be guaranteed
by a firm that is a bank, broker, dealer, credit union, savings association or
other entity which is a member in good standing of the Securities Transfer
Agents Medallion Program (an "Eligible Institution"), except in cases where
Shares or Rights are tendered (i) by a registered holder of Shares and Rights
who has not completed either the box entitled "Special Payment Instructions" or
the box entitled "Special Delivery Instructions" on the Letter of Transmittal
or (ii) for the account of an Eligible Institution. See Instruction 1 of the
Letter of Transmittal.
 
  If the Share Certificates or the Rights Certificates are registered in the
name of a person other than the signer of the Letter of Transmittal, or if
payment is to be made, or Share Certificates or Rights Certificates for Shares
or Rights not accepted for payment or not tendered are to be returned, to a
person other than the registered holder(s), then the tendered Share
Certificates or Rights Certificates, as the case may be, must be endorsed or
accompanied by appropriate stock powers, in either case, signed exactly as the
name(s) of the registered holder(s) appear on such certificates, with the
signature(s) on such certificates or stock powers guaranteed by an Eligible
Institution as provided above and in the Letter of Transmittal. See
Instructions 1 and 5 of the Letter of Transmittal.
 
  If Share Certificates and Rights Certificates are forwarded separately to the
Depositary, a properly completed and duly executed Letter of Transmittal (or a
facsimile thereof) must accompany each such delivery.
 
  Guaranteed Delivery. If a shareholder desires to tender Shares and Rights
pursuant to the Offer and such shareholder's Share Certificates or Rights
Certificates are not immediately available (including because Rights
Certificates have not yet been distributed by the Company), or such shareholder
cannot deliver the Share Certificates or Rights Certificates and all other
required documents to reach the Depositary on or prior to the Expiration Date,
or such shareholder cannot complete the procedure for delivery by book-entry
transfer on a timely basis, such Shares and Rights may nevertheless be
tendered, provided that all of the following conditions are satisfied:
 
    (i) such tender is made by or through an Eligible Institution;
 
    (ii) a properly completed and duly executed Notice of Guaranteed
  Delivery, substantially in the form made available by the Purchaser, is
  received by the Depositary, as provided below, on or prior to the
  Expiration Date; and
 
    (iii) the Share Certificates or Rights Certificates, as the case may be
  (or a Book-Entry Confirmation), representing all tendered Shares or Rights,
  in proper form for transfer, in each case together with the Letter of
  Transmittal (or a facsimile thereof), properly completed and duly executed,
  with any required
 
                                       9
<PAGE>
 
  signature guarantees (or, in the case of a book-entry transfer, an Agent's
  Message) and any other documents required by the Letter of Transmittal are
  received by the Depositary within (a) in the case of Shares, five Nasdaq
  National Market ("NNM") trading days after the date of execution of such
  Notice of Guaranteed Delivery or (b) in the case of Rights, a period ending
  on the later of (1) five NNM trading days after the date of execution of
  such Notice of Guaranteed Delivery and (2) five business days after the
  date the Rights Certificates are distributed to shareholders of the
  Company.
 
  The Notice of Guaranteed Delivery may be delivered by hand or transmitted by
telegram, facsimile transmission or mail to the Depositary and must include a
guarantee by an Eligible Institution in the form set forth in such Notice of
Guaranteed Delivery.
 
  Notwithstanding any other provision hereof, payment for Shares accepted for
payment pursuant to the Offer will in all cases be made only after timely
receipt by the Depositary of Share Certificates for, or of Book-Entry
Confirmation with respect to, such Shares, and if the Distribution Date has
occurred, Rights Certificates for, or a Book-Entry Confirmation, if available,
with respect to, the associated Rights (unless the Purchaser elects, in its
sole discretion, to make payment for such Shares pending receipt of the Rights
Certificates for, or a Book-Entry Confirmation with respect to, such Rights), a
properly completed and duly executed Letter of Transmittal (or a facsimile
thereof), together with any required signature guarantees (or, in the case of a
book-entry transfer, an Agent's Message), and any other documents required by
the Letter of Transmittal. Accordingly, payment might not be made to all
tendering shareholders at the same time, and will depend upon when Share
Certificates (or Rights Certificates) or Book-Entry Confirmations of such
Shares (or Rights, if available) are received into the Depositary's account at
a Book-Entry Transfer Facility.
 
  If, on or before the Expiration Date, the Rights have been redeemed by the
Company's Board of Directors, the guaranteed delivery procedure with respect to
Rights Certificates and the requirement for the tender of Rights will no longer
apply.
 
  Appointment as Proxy. By executing the Letter of Transmittal, a tendering
shareholder irrevocably appoints designees of the Purchaser, and each of them,
as such shareholder's attorneys-in-fact and proxies, with full power of
substitution, in the manner set forth in the Letter of Transmittal, to the full
extent of such shareholder's rights with respect to the Shares and Rights
tendered by such shareholder and accepted for payment and paid for by the
Purchaser (and with respect to any and all other Shares or Rights or other
securities issued or issuable in respect of such Shares on or after the date
hereof). All such powers of attorney and proxies shall be considered
irrevocable and coupled with an interest in the tendered Shares and Rights.
Such appointment will be effective when, and only to the extent that, the
Purchaser accepts such Shares and Rights for payment and deposits the purchase
price therefor with the Depositary. Upon such payment, all prior powers of
attorney and proxies given by such shareholder with respect to such Shares and
Rights (and such other shares and securities) will be revoked without further
action, and no subsequent powers of attorney and proxies may be given nor any
subsequent written consents executed by such shareholder (and, if given or
executed, will not be deemed effective). The designees of the Purchaser will be
empowered to exercise all voting and other rights of such shareholder as they
in their sole discretion may deem proper at any annual or special meeting of
the Company's shareholders or any adjournment or postponement thereof, by
written consent in lieu of any such meeting or otherwise. The Purchaser
reserves the right to require that, in order for Shares and Rights to be deemed
validly tendered, immediately upon the Purchaser's payment for such Shares, the
Purchaser must be able to exercise full voting rights with respect to such
Shares, Rights and other securities, including voting at any meeting of
shareholders.
 
  Determination of Validity. All questions as to the validity, form,
eligibility (including time of receipt) and acceptance for payment of any
tender of Shares and Rights will be determined by the Purchaser, in its sole
discretion, which determination shall be final and binding on all parties. The
Purchaser reserves the absolute right to reject any and all tenders determined
by it not to be in proper form or the acceptance of or payment for which may,
in the opinion of its counsel, be unlawful. The Purchaser also reserves the
absolute right to waive any of the conditions of the Offer or any defect or
irregularity in any tender of Shares and
 
                                       10
<PAGE>
 
Rights of any particular shareholder whether or not similar defects or
irregularities are waived in the case of other shareholders. No tender of
Shares will be deemed to have been validly made until all defects and
irregularities have been cured or waived. None of the Purchaser, the Parent,
any of their affiliates or assigns, the Dealer Manager, the Depositary, the
Information Agent or any other person will be under any duty to give
notification of any defects or irregularities in tenders or incur any liability
for failure to give any such notification. The Purchaser's interpretation of
the terms and conditions of the Offer (including the Letter of Transmittal and
the instructions thereto) will be final and binding.
 
  BACKUP FEDERAL TAX WITHHOLDING. UNDER THE FEDERAL INCOME TAX LAWS, THE
DEPOSITARY MAY, UNDER CERTAIN CIRCUMSTANCES, BE REQUIRED TO WITHHOLD 31% OF THE
AMOUNT OF ANY PAYMENTS MADE TO CERTAIN SHAREHOLDERS PURSUANT TO THE OFFER. TO
PREVENT BACKUP FEDERAL INCOME TAX WITHHOLDING WITH RESPECT TO PAYMENT TO
CERTAIN SHAREHOLDERS OF THE PURCHASE PRICE OF SHARES PURCHASED PURSUANT TO THE
OFFER, EACH SUCH SHAREHOLDER MUST PROVIDE THE DEPOSITARY WITH SUCH
SHAREHOLDER'S CORRECT TAXPAYER IDENTIFICATION NUMBER AND CERTIFY THAT SUCH
SHAREHOLDER IS NOT SUBJECT TO BACKUP FEDERAL INCOME TAX WITHHOLDING BY
COMPLETING THE SUBSTITUTE FORM W-9 INCLUDED IN THE LETTER OF TRANSMITTAL. SEE
INSTRUCTION 9 OF THE LETTER OF TRANSMITTAL.
 
  Other Requirements. The Purchaser's acceptance for payment of Shares and, if
applicable, Rights tendered pursuant to any of the procedures described above
will constitute a binding agreement between the tendering shareholder and the
Purchaser upon the terms and subject to the conditions of the Offer.
 
  4. WITHDRAWAL RIGHTS. Except as otherwise provided in this Section 4, tenders
of Shares and Rights made pursuant to the Offer are irrevocable, except that
Shares and Rights tendered pursuant to the Offer may be withdrawn at any time
on or prior to the Expiration Date and, unless theretofore accepted for payment
by the Purchaser pursuant to the Offer, may also be withdrawn at any time after
December 23, 1994 (or such later date as may apply in case the Offer is
extended). A withdrawal of Shares or Rights shall also constitute a withdrawal
of the associated Rights or Shares, as applicable.
 
  If the Purchaser extends the Offer, is delayed in its acceptance for payment
of Shares and Rights or is unable to purchase Shares and Rights validly
tendered pursuant to the Offer for any reason, then, without prejudice to the
Purchaser's rights under the Offer, the Depositary may nevertheless, on behalf
of the Purchaser, retain tendered Shares and Rights, and such Shares and Rights
may not be withdrawn except to the extent that tendering shareholders are
entitled to and duly exercise withdrawal rights as described in this Section 4.
Any such delay will be accompanied by an extension of the Offer to the extent
required by law.
 
  In order for a withdrawal to be effective, a written, telegraphic or
facsimile transmission notice of withdrawal must be timely received by the
Depositary at one of its addresses set forth on the back cover of this Offer to
Purchase. Any notice of withdrawal must specify the name of the person who
tendered the Shares or Rights to be withdrawn, the number of Shares or Rights
to be withdrawn and the name of the registered holder, if different from that
of the person who tendered such Shares or Rights. If Share Certificates or
Rights Certificates to be withdrawn have been delivered or otherwise identified
to the Depositary, then, prior to the physical release of such certificates,
the serial numbers shown on such certificates must be submitted to the
Depositary and the signature(s) on the notice of withdrawal must be guaranteed
by an Eligible Institution unless such Shares or Rights have been tendered for
the account of any Eligible Institution. If Shares or Rights have been tendered
pursuant to the procedure for book-entry transfer as set forth in Section 3,
any notice of withdrawal must specify the name and number of the account at the
Book-Entry Transfer Facility to be credited with the withdrawn Shares or Rights
and must otherwise comply with the procedures of such Book-Entry Transfer
Facility, in which case a notice of withdrawal will be effective if delivered
to the Depositary by any method of delivery described in the first sentence of
this paragraph.
 
  All questions as to the form and validity (including time of receipt) of any
notice of withdrawal will be determined by the Purchaser, in its sole
discretion, whose determination will be final and binding. None of the
Purchaser, the Parent, any of their affiliates or assigns, the Dealer Manager,
the Depositary, the
 
                                       11
<PAGE>
 
Information Agent or any other person will be under any duty to give
notification of any defects or irregularities in any notice of withdrawal or
incur any liability for failure to give any such notification.
 
  Any Shares or Rights properly withdrawn will thereafter be deemed not to have
been validly tendered for purposes of the Offer. However, withdrawn Shares or
Rights may be re-tendered at any time prior to the Expiration Date by following
one of the procedures described in Section 3.
 
  5. CERTAIN FEDERAL INCOME TAX CONSEQUENCES. The summary of tax consequences
set forth below is for general information only. The tax treatment of each
shareholder will depend in part upon his particular situation. Special tax
consequences not described herein may be applicable to particular classes of
taxpayers, such as financial institutions, broker-dealers, persons who are not
citizens or residents of the United States, shareholders who acquired their
Shares through the exercise of an employee stock option or otherwise as
compensation, and persons who received payments in respect of options to
acquire Shares. ALL SHAREHOLDERS SHOULD CONSULT WITH THEIR OWN TAX ADVISORS AS
TO THE PARTICULAR TAX CONSEQUENCES OF THE OFFER AND THE MERGER TO THEM,
INCLUDING THE APPLICABILITY AND EFFECT OF ANY STATE, LOCAL AND FOREIGN TAX
LAWS.
 
  The receipt of cash pursuant to the Offer or the Merger will be a taxable
transaction for federal income tax purposes and may also be a taxable
transaction under applicable state, local, foreign or other tax laws.
Generally, a shareholder will recognize gain or loss for federal income tax
purposes in an amount equal to the difference between the cash received and the
shareholder's adjusted tax basis in the Shares and the Rights. For federal
income tax purposes, such gain or loss will be a capital gain or loss if the
Shares are a capital asset in the hands of the shareholder, and a long-term
capital gain or loss if the shareholder's holding period is more than one year
as of the date the Purchaser accepts such Shares for payment pursuant to the
Offer or the effective date of the Merger, as the case may be. There are
limitations on the deductibility of capital losses.
 
  6. PRICE RANGE OF SHARES; DIVIDENDS. Based upon publicly available
information, the Shares are traded in the over-the-counter-market and quoted on
the NNM under the symbol PBEN. The following table sets forth, for the fiscal
quarters indicated, the high and low sales prices per Share on the NNM and the
amounts of cash dividends paid or declared per Share for each such quarter, all
based on publicly available sources.
 
<TABLE>
<CAPTION>
                                                    HIGH      LOW    DIVIDENDS
                                                    ----      ---    ---------
<S>                                                 <C>       <C>    <C>      
Fiscal Year Ended January 31, 1993:                                           
  First Quarter.................................... $26 3/4   $21       $.03  
  Second Quarter...................................  35 1/2    25        .03  
  Third Quarter....................................  35 3/4    26 1/4    .03  
  Fourth Quarter...................................  36        26 1/2    .03  
Fiscal Year Ended January 31, 1994:                                           
  First Quarter....................................  30        13 1/4    .03  
  Second Quarter...................................  22 3/4    16        .03  
  Third Quarter....................................  21 3/4    15 3/4    .03  
  Fourth Quarter...................................  21        14 1/2    .03  
Fiscal Year Ending January 31, 1995:                                          
  First Quarter....................................  22 3/4    19        .03  
  Second Quarter...................................  21 3/4    16 3/4    .03  
  Third Quarter (through October 24, 1994).........  24 1/2    15 1/4      *   
</TABLE>
- --------
* As of October 24, 1994, to the Parent's knowledge, no public announcement
 regarding the payment of a dividend with respect to the third quarter ending
 October 31, 1994 had been made by the Company. The Purchaser has no reason to
 believe that the Company plans to vary its current practice of paying a cash
 dividend of $.03 per Share per quarter.
 
  On October 24, 1994, the last trading day prior to the public announcement of
the Offer, the closing sale price per Share reported on the NNM was $23 1/2. On
October 6, 1994, the last trading day prior to the Company's issuance of a
press release announcing the receipt by the Company from the Parent of an offer
to
 
                                       12
<PAGE>
 
acquire the Company in a merger transaction in which shareholders would receive
$21 per Share in cash, the closing sale price per Share reported on the NNM was
$18.
 
  SHAREHOLDERS ARE URGED TO OBTAIN A CURRENT MARKET QUOTATION FOR THE SHARES.
 
  The Purchaser believes, based upon publicly available information, that the
Rights are currently attached to the outstanding Shares and may not be traded
separately. As a result, the sales prices per Share set forth above are also
the high and low sales prices per Share and associated Right. As a result of
the commencement of the Offer, the Distribution Date may be as early as
November 3, 1994, after which the Rights could begin trading separately from
the Shares. See Section 11. In such event, shareholders are urged to obtain a
current market quotation, if any, for the Rights. Unless, on or before the
Expiration Date, the Rights have been redeemed by the Company's Board of
Directors, holders of Shares will be required to tender one Right for each
Share tendered in order to effect a valid tender of such Share. Accordingly,
shareholders who sell their Rights separately from their Shares and do not
otherwise acquire Rights may not be able to satisfy the requirements of the
Offer for a valid tender of Shares.
 
  7. CERTAIN INFORMATION CONCERNING THE COMPANY. The Company is a Delaware
corporation, with its principal executive offices located at 9401 Indian Creek
Parkway, Building #40, Suite 300, P.O. Box 25905, Overland Park, Kansas 66225.
 
  According to the Company's 1994 Form 10-K, the Company is primarily engaged
in the development, manufacture and sale of products relating to respiration.
Such products are used in a wide variety of health care settings and on
aircraft. The Company is organized in three main business areas: (i) the
hospital market, (ii) the home respiratory care, medical gases and physician
markets and (iii) the general and commercial aviation market.
 
  The Company is subject to the disclosure requirements of the Exchange Act and
in accordance therewith is required to file reports and other information with
the Commission relating to its business, financial condition and other matters.
Such reports and other information are available for inspection at the
Commission's public reference facilities at 450 Fifth Street, N.W., Washington,
DC 20549 and should also be available for inspection and copying at prescribed
rates at the regional offices of the Commission located at Seven World Trade
Center, 13th Floor, New York, New York 10048 and Northwestern Atrium Center,
500 West Madison Street, Suite 1400, Chicago, Illinois 60661. Copies may also
be obtained by mail, upon payment of the Commission's customary fees, from the
Commission's principal office at 450 Fifth Street, N.W., Washington, DC 20549.
In addition, certain material filed by the Company should also be available for
inspection at the offices of the NASD, Reports Section, 1735 K Street, N.W.,
Washington, DC 20006.
 
  Except as specifically set forth herein, the information concerning the
Company set forth in this Section 7 and elsewhere in this Offer to Purchase has
been taken from, or is based upon, publicly available documents on file with
the Commission, and shareholders are urged to review the publicly available
information concerning the Company before acting on the Offer. Although neither
the Purchaser nor the Parent has any knowledge that would indicate that any
statements contained herein which are based on such documents are untrue,
neither the Purchaser nor the Parent takes any responsibility for the accuracy
or completeness of the information concerning the Company contained in such
documents or herein or for any failure by the Company to disclose events which
may have affected or may affect the significance or accuracy of any such
information but that are unknown to the Purchaser or the Parent.
 
  Set forth below is certain consolidated financial data with respect to the
Company and its subsidiaries excerpted or derived from the information in the
1994 Form 10-K and the July 1994 Form 10-Q. More comprehensive financial
information is included in such reports and in other documents filed by the
Company with the Commission (which may be inspected or obtained in the manner
set forth above), and the following data is qualified in its entirety by
reference to such reports and other documents and all of the financial
information (including any related notes) contained therein or incorporated by
reference.
 
                                       13
<PAGE>
 
                          PURITAN-BENNETT CORPORATION
 
                      SELECTED CONSOLIDATED FINANCIAL DATA
                     (IN THOUSANDS, EXCEPT PER SHARE DATA)
 
<TABLE>
<CAPTION>
                                                                TRANSITION
                             SIX MONTHS         YEAR ENDED      PERIOD: ONE     YEAR
                          ENDED JULY 31,(1)     JANUARY 31,     MONTH ENDED    ENDED
                          -----------------  ------------------ JANUARY 31, DECEMBER 31,
                            1994     1993      1994      1993      1992         1991
                          -------- --------  --------  -------- ----------- ------------
<S>                       <C>      <C>       <C>       <C>      <C>         <C>
STATEMENT OF OPERATIONS
 DATA:
Net Sales...............  $164,401 $153,305  $309,255  $300,060   $19,682     $256,122
Restructuring Charges...       --     9,014    43,169       --        --           --
Net Income (Loss) Before
 Cumulative Effect......     7,968   (3,114)  (31,779)   14,595    (2,291)         574
Cumulative Effect of
 Accounting Changes (Net
 of Income Taxes).......       --    (2,755)   (2,890)      --     (3,059)         --
Net Income (Loss).......     7,968   (5,869)  (34,669)   14,595    (5,350)         574
Pro Forma Net Income
 (Loss) Assuming the
 Effect of the Change in
 Accounting for Deferred
 Compensation is Applied
 Retroactively..........       --       --        --        --     (2,291)      (1,059)
PER SHARE DATA:
Net Income (Loss) Before
 Cumulative Effect Per
 Common Share...........       .64     (.26)    (2.66)     1.24      (.20)         .05
Cumulative Effect of
 Accounting Changes Per
 Common Share (Net of
 Income Taxes)..........       --      (.23)     (.24)      --       (.26)         --
Net Income (Loss) Per
 Common Share...........       .64     (.49)    (2.90)     1.24      (.46)         .05
Pro Forma Net Income
 (Loss) Per Common Share
 Assuming the Effect of
 the Change in
 Accounting for Deferred
 Compensation is Applied
 Retroactively..........       --       --        --        --       (.20)        (.09)
</TABLE>
 
<TABLE>
<CAPTION>
                                                JULY 31, JANUARY 31, JANUARY 31,
                                                1994(1)     1994        1993
                                                -------- ----------- -----------
<S>                                             <C>      <C>         <C>
BALANCE SHEET DATA:
Net Working Capital............................ $ 79,173  $ 51,882    $ 81,086
Total Assets...................................  265,649   256,594     244,408
Long-Term Debt, Less Current Maturities........   63,336    38,656      42,840
Stockholders' Equity...........................  115,952   107,712     133,723
</TABLE>
- --------
(1)Derived from unaudited financial statements.
 
  8. CERTAIN INFORMATION CONCERNING THE PURCHASER AND THE PARENT.
 
  The Parent is a Delaware corporation, with its principal executive offices
(as well as those of the Purchaser) located at 81 Wyman Street, Waltham,
Massachusetts 02254.
 
  The Parent and its subsidiaries develop, manufacture and market analytical
and environmental monitoring and analysis instruments, biomedical products
including heart-assist devices and emammography systems, papermaking and
recycling equipment, alternative-energy systems, industrial process equipment,
biomedical products and other specialized products. The Parent and its
subsidiaries also provide environmental and metallurgical services and conduct
advanced technology research and development. The Parent conducts its business
through its divisions and wholly owned subsidiaries, as well as majority-owned
subsidiaries that are partially owned by the public or private investors. The
Parent's common stock is listed on the New York Stock Exchange.
 
  The Purchaser, a Delaware corporation and a wholly owned subsidiary of the
Parent, was organized in connection with the Offer and has not carried on any
activities to date other than those incident to its
 
                                       14
<PAGE>
 
formation and the commencement of the Offer. Until immediately prior to the
time that the Purchaser will purchase Shares pursuant to the Offer, it is not
anticipated that the Purchaser will have any significant assets or liabilities
or engage in activities other than those incident to its formation and
capitalization and the transactions contemplated by the Offer. Because the
Purchaser has minimal assets and capitalization, no meaningful financial
information is available.
 
  The name, citizenship, business address, principal occupation or employment,
and five year employment history of each of the directors and executive
officers of the Purchaser and the Parent and certain other information are set
forth in Schedule I hereto.
 
  Except as described in this Offer to Purchase, none of the Purchaser, the
Parent nor, to the best knowledge of the Purchaser and the Parent, any of the
persons listed on Schedule I hereto or any associate or majority-owned
subsidiary of the Purchaser, the Parent or any of the persons so listed,
beneficially owns or has a right to acquire directly or indirectly any Shares,
and none of the Purchaser, the Parent nor, to the best knowledge of the
Purchaser and the Parent, any of the persons or entities referred to above, or
any of the respective executive officers, directors or subsidiaries of any of
the foregoing, has effected any transactions in the Shares during the past 60
days. The Parent has effected the following transaction in the Shares during
the past 60 days:
 
<TABLE>
<CAPTION>
                                                             NUMBER     PRICE
      TYPE OF TRANSACTION                            DATE   OF SHARES PER SHARE
      -------------------                           ------- --------- ---------
      <S>                                           <C>     <C>       <C>
      Open Market Purchase......................... 8/29/94   8,000    $17.00
</TABLE>
 
  The Parent currently beneficially owns an aggregate of 610,000 Shares,
representing approximately 4.9% of the Shares outstanding (approximately 4.5%
on a fully diluted basis), based on the number of Shares outstanding at
September 7, 1994 and the number of options outstanding at January 31, 1994.
 
  Except as set forth in this Offer to Purchase, none of the Purchaser, the
Parent nor, to the best knowledge of the Purchaser and the Parent, any of the
persons listed on Schedule I hereto, has any contract, arrangement,
understanding or relationship with any other person with respect to any
securities of the Company, including, but not limited to, contracts,
arrangements, understandings or relationships concerning the transfer or voting
of any of such securities, joint ventures, loan or option arrangements, puts or
calls, guaranties of loans, guaranties against loss or the giving or
withholding of proxies. Except as set forth in this Offer to Purchase, none of
the Purchaser, the Parent nor, to the best knowledge of the Purchaser and the
Parent, any of the persons listed on Schedule I hereto, has had since January
1, 1991, any business relationships or transactions with the Company or any of
its executive officers, directors or affiliates that are required to be
reported under the rules and regulations of the Commission applicable to the
Offer. Except as set forth in this Offer to Purchase, since January 1, 1991,
there have been no contacts, negotiations or transactions between any of the
Parent, the Purchaser, any subsidiary of the Parent or the Purchaser or, to the
best knowledge of the Purchaser and the Parent, any of the persons listed in
Schedule I hereto, on the one hand, and the Company or its affiliates, on the
other hand, concerning a merger, consolidation or acquisition, a tender offer
or other acquisition of securities, an election of directors, or a sale or
other transfer of a material amount of assets.
 
  The Parent is subject to the disclosure requirements of the Exchange Act and
in accordance therewith is required to file reports and other information with
the Commission relating to its business, financial condition and other matters.
Such reports are available for inspection and copying at prescribed rates at
the offices of the Commission as set forth in Section 7. In addition, such
material should also be available for inspection at the library of the New York
Stock Exchange, 20 Broad Street, New York, New York 10005.
 
  Set forth below is certain consolidated financial data with respect to the
Parent and its subsidiaries excerpted or derived from the audited consolidated
financial statements included in the Parent's Annual Report on Form 10-K for
the fiscal year ended January 1, 1994 and the unaudited consolidated financial
statements included in the Parent's Quarterly Report on Form 10-Q for the
fiscal quarter ended July 2, 1994. More comprehensive financial information is
included in such reports and in other documents filed by the Parent with the
Commission (which may be inspected or obtained in the manner set forth above),
and the following data is qualified in its entirety by reference to such
reports and other documents and all of the financial information (including any
related notes) contained therein or incorporated by reference.
 
                                       15
<PAGE>
 
                          THERMO ELECTRON CORPORATION
 
                      SELECTED CONSOLIDATED FINANCIAL DATA
                     (IN THOUSANDS, EXCEPT PER SHARE DATA)
 
<TABLE>
<CAPTION>
                         SIX MONTHS ENDED(1)             YEAR ENDED
                         ------------------- ----------------------------------
                          JULY 2,   JULY 3,  JANUARY 1, JANUARY 2, DECEMBER 28,
                           1994      1993       1994       1993        1991
                         --------- --------- ---------- ---------- ------------
<S>                      <C>       <C>       <C>        <C>        <C>
INCOME STATEMENT DATA:
 Revenues............... $ 745,442 $ 593,212 $1,249,718  $948,972    $805,484
 Income Before Cumula-
  tive Effect of Change
  in Accounting Princi-
  ple...................    46,691    33,054     76,633    60,594      47,054
 Net Income.............    46,691    33,054     76,633    59,156      47,054
PER SHARE DATA:
 Earnings per Share Be-
  fore Cumulative Effect
  of Change in Account-
  ing Principle:
  Primary...............       .97       .81       1.75      1.51        1.31
  Fully Diluted.........       .86       .73       1.57      1.41        1.23
 Earnings per Share:
  Primary...............       .97       .81       1.75      1.48        1.31
  Fully Diluted.........       .86       .73       1.57      1.38        1.23
</TABLE>
 
<TABLE>
<CAPTION>
                                                JULY 2,   JANUARY 1, JANUARY 2,
                                                1994(1)      1994       1993
                                               ---------- ---------- ----------
<S>                                            <C>        <C>        <C>
BALANCE SHEET DATA:
 Working Capital.............................. $1,120,032 $  828,297 $  503,364
 Total Assets.................................  2,933,961  2,473,710  1,818,265
 Long-term Obligations........................  1,132,948    647,461    494,152
 Minority Interest............................    298,898    277,681    164,293
 Shareholders' Investment.....................    892,711    858,523    552,901
</TABLE>
- --------
(1)Derived from unaudited financial statements.
 
  9. SOURCE AND AMOUNT OF FUNDS. The total amount of funds required by the
Purchaser to purchase all of the outstanding Shares (on a fully diluted basis)
and pay related fees and expenses is expected to be approximately $320,000,000.
The Purchaser will obtain such funds through capital contributions from the
Parent. The Parent currently has cash and cash equivalents in excess of such
amount available for the purchase of Shares and intends to use such funds to
capitalize the Purchaser, which in turn will use the funds to pay for tendered
Shares. Obtaining financing is not a condition of the Offer.
 
  10. BACKGROUND OF THE OFFER; CONTACTS WITH THE COMPANY. On June 23, 1994,
Roger Herd, Managing Director of Thermo Instruments Australia Pty., Ltd., a
subsidiary of the Parent, met with Burton A. Dole, Jr., President of the
Company, at the Company's offices in Carlsbad, California to discuss issues
pertaining to manufacturing in Ireland.
 
  On July 15, 1994, John W. Wood, Jr., Chief Executive Officer of Thermedics
Inc., a subsidiary of the Parent, met with Mr. Dole at the Company's
headquarters in Overland Park, Kansas, to discuss matters of potential mutual
interest. At this meeting, Mr. Wood provided Mr. Dole with some general
background material on the Parent, indicated that the Parent had acquired
shares of stock in the Company, and expressed preliminary interest in a
possible acquisition of the Company. Mr. Dole stated that the current market
price of the Shares (the last reported sales price for which was $18 3/16 on
July 14, 1994) was significantly lower than historical prices and that in his
view the current market price did not reflect the true value of the Shares. On
that basis, he replied that he was not interested in pursuing a sale of the
Company, but was willing to meet with the Parent's Chief Executive Officer.
 
 
                                       16
<PAGE>
 
  On July 20, 1994, Dr. George N. Hatsopoulos, Chief Executive Officer of the
Parent, met with Mr. Dole in Boston, Massachusetts. Dr. Hatsopoulos provided
Mr. Dole with an overview of the Parent's businesses and reiterated the
Parent's interest in a possible acquisition of the Company. Mr. Dole repeated
his views as to the value of the Shares and stated that he was not interested
in a possible acquisition, but agreed to meet with Dr. Hatsopoulos again in
Boston on September 21, 1994.
 
  On July 29, 1994, Mr. Dole called Mr. Wood to discuss whether the Parent
might be interested in purchasing the blood gas monitoring business of the
Company. Mr. Wood indicated that the Parent was not interested in acquiring
this business alone.
 
  On September 19, 1994, Mr. Dole called Dr. Hatsopoulos to cancel their
scheduled meeting on September 21, 1994. Dr. Hatsopoulos again expressed
interest to Mr. Dole in a possible acquisition and suggested that the Company
hire an investment banker to evaluate any offer the Parent might make. Mr. Dole
said that the Company was not interested in pursuing a sale at that time in
light of the factors he previously discussed with Mr. Wood and Dr. Hatsopoulos,
but that the Company would retain an investment banker.
 
  On September 22, 1994, Dr. Hatsopoulos called Mr. Dole, who informed Dr.
Hatsopoulos that the Company had hired an investment banker to advise it.
 
  On September 27, 1994, Mr. Dole called Dr. Hatsopoulos and said that the
Company's Board of Directors would meet on October 10, 1994 to consider the
Parent's interest in acquiring the Company.
 
  On September 27, 1994, Seth H. Hoogasian, the Parent's General Counsel, and
Daniel C. Weary, a Director of the Company and the Company's outside General
Counsel, discussed by telephone a possible meeting of representatives of the
Company and the Parent before the October 10, 1994 meeting of the Company's
Board of Directors. Mr. Weary stated that the Company would not agree to such a
meeting before the October 10, 1994 meeting of the Company's Board of
Directors.
 
  On September 29, 1994, Mr. Hoogasian and Mr. Weary discussed by telephone
possible scenarios under which the Company would be willing to meet with the
Parent to discuss a potential acquisition. Mr. Weary reiterated the Company's
position that no meeting would occur before October 10, 1994.
 
  On September 30, 1994, Mr. Hoogasian called Mr. Weary to discuss the increase
in trading volume in the Shares that day.
 
  On October 3, 1994, Mr. Weary called Mr. Hoogasian to inform him that the
Company was unaware of any reason for the increased trading volume that
occurred on September 30, 1994.
 
  On October 5, 1994, Mr. Weary called Mr. Hoogasian to inform him that the
Company was going to issue a press release that day pertaining to 510(k)
approval by the U.S. Food and Drug Administration of certain of the Company's
products.
 
  On October 6, 1994, Mr. Hoogasian called Mr. Weary and informed him that, in
light of the increase in the price of the Shares since September 30, 1994, the
Parent was going to send a letter to Mr. Dole outlining a proposal for a
negotiated merger transaction.
 
 
                                       17
<PAGE>
 
  On October 6, 1994, Dr. Hatsopoulos sent the following letter to Mr. Dole:
 
                                                                 October 6, 1994
 
Mr. Burton A. Dole
President
Puritan-Bennett Corporation
9401 Indian Creek Parkway
Overland Park, Kansas 66225
 
Dear Burton:
 
  As you know, Thermo Electron Corporation ("Thermo") has been evaluating for
some time the possibility of a business combination with Puritan-Bennett
Corporation ("Puritan"), and we have concluded that such a combination would be
in the best interests of the stockholders of both corporations.
 
  During the past few weeks you and I have spoken several times regarding
Thermo's interest in Puritan. I understand that a meeting of your Board of
Directors has been scheduled for October 10, 1994. However, in light of the
seriousness of our interest and the magnitude of the transaction, we believe
that the interests of both corporations will be best served if we commence
active negotiation of a merger transaction immediately. I have been authorized
by our Board of Directors to propose a cash merger of our two companies in
which all Puritan shareholders would receive $21 for each outstanding share of
Puritan's stock, which represents a substantial premium over recent market
prices for Puritan's common stock. Our proposal is based on publicly available
information regarding Puritan. We currently have sufficient cash to complete
the transaction. At this time, we are interested in pursuing a transaction only
if it has been approved by your Board of Directors.
 
  Over the past 20 years, Thermo has completed over 75 acquisitions, including
the acquisitions of two public companies, Finnigan Corporation and Nicolet
Instrument Corporation. We believe that in virtually all of these acquisitions
we have been able to add value for our own shareholders as well as for the
employees and customers of the acquired companies. As you know, Thermo is a
decentralized organization in which each operating unit has substantial
autonomy over its day-to-day operations. We believe that this structure has
created an entrepreneurial environment that has contributed greatly to our
success. Like our other subsidiaries, Puritan would continue to operate as a
separate entity with its own management.
 
  We and our advisors are prepared to meet with you immediately to work on a
merger agreement. Working together, I'm sure that we will be able to reach
agreement on all of the details and enter into an agreement very quickly. Given
the seriousness of our offer and the substantial premium that we are proposing,
I'm sure you will agree with me that the interests of your shareholders would
best be served by the immediate commencement of negotiations and consideration
of our proposal.
 
  I look forward to hearing from you shortly and commencing what I hope will be
a long and mutually beneficial relationship.
 
                                          Sincerely,
 
                                          /s/ George N. Hatsopoulos
 
                                          George N. Hatsopoulos
                                          Chairman of the Board and Chief
                                           Executive Officer
 
 
                                       18
<PAGE>
 
  On October 6, 1994, the Company issued a press release describing the
Parent's proposal and stating that its Board of Directors would in due course
review the proposal.
 
  On October 7, 1994, the Parent issued a press release summarizing its October
6, 1994 proposal to the Company.
 
  On October 11, 1994, Mr. Dole informed Mr. Hoogasian that the Company was
issuing a press release stating that its Board of Directors had rejected the
Parent's offer.
 
  On October 12, 1994, Dr. Hatsopoulos sent the following letter to Mr. Dole,
and the Parent issued a press release summarizing its contents:
 
                                                                October 12, 1994
 
VIA TELECOPY
 
Mr. Burton A. Dole, Jr.
President
Puritan-Bennett Corporation
9401 Indian Creek Parkway
Overland Park, Kansas 66225
 
Dear Burton:
 
  I was disappointed in the response of your Board of Directors to our merger
proposal of $21 per share, and in your refusal to meet with us to discuss the
terms of a transaction that would be satisfactory to both parties. We have been
seeking an opportunity to meet with you for several weeks, and we believe that
the best interests of your shareholders cannot be served unless you meet with
us to discuss our proposal.
 
  As I have stated previously, we continue to be interested in pursuing a
negotiated merger transaction with Puritan-Bennett. I want to stress again that
our desire is to complete a transaction on an amicable basis. It is not our
intention or tradition to engage in auctions for companies. In an effort to
raise our offer to a level that would be acceptable to your Board of Directors,
we have reevaluated certain of the assumptions underlying our original offer of
$21 per share. Among other things, we have considered the response of
securities analysts to our original offer. As a result, we are now prepared to
offer $24 per share of outstanding common stock in a negotiated merger
transaction.
 
  At this stage I'm sure you appreciate the seriousness of our offer, and I'm
confident that you will act in the best interests of your shareholders in
considering the proposed merger. However, I do not believe that you can respond
to our offer in an informed manner until you have met with us to discuss all of
the relevant terms of the proposal. In that regard, we are prepared to fly to
Kansas City at your earliest convenience to discuss the details of our
proposal.
 
  I look forward to hearing from you soon.
 
                                          Sincerely,
 
                                          /s/ George
 
                                          George N. Hatsopoulos
                                          Chairman of the Board and Chief
                                           Executive Officer
 
 
                                       19
<PAGE>
 
  On October 19, 1994, Dr. Hatsopoulos received the following letter from the
Company:
 
                                                                October 19, 1994
 
BY TELECOPIER
 
George N. Hatsopoulos
Chairman of the Board and
 Chief Executive Officer
Thermo Electron Corporation
81 Wyman Street
Waltham, MA 02254
 
Dear George:
 
  We have received your letter of October 12, 1994 and it will be reviewed by
the Board of Directors of Puritan-Bennett Corporation at a meeting to be held
in the near future.
 
  In your letter, you imply that there may be additional terms of Thermo
Electron's proposal that are not described in the letter and request a meeting
to discuss those terms. I would suggest that if there are any additional terms
that are relevant to the consideration of your proposal, those additional terms
should be communicated to me in writing for presentation to the Board. In
addition, if you wish to clarify or amplify any aspect of your proposal, Conrad
L. Bringsjord of Smith Barney, the Company's financial advisor, is available
and can be reached at (212) 698-8455.
 
                                          Very truly yours,
 
                                          /s/ Burton A. Dole, Jr.
 
                                          Burton A. Dole, Jr.
                                          Chairman of the Board, President and
                                           Chief Executive Officer
 
  On October 24, 1994, Dr. Hatsopoulos called Mr. Dole's office to notify Mr.
Dole that the Parent intended to commence the Offer on October 25, 1994. Dr.
Hatsopoulos was told that Mr. Dole was traveling. Mr. Hoogasian then called Mr.
Weary and stated that the Parent planned to begin the Offer on October 25, 1994
and was sending a letter to such effect to Mr. Weary for delivery to Mr. Dole.
Dr. Hatsopoulos then sent the following letter to Mr. Dole.
 
                                                                October 24, 1994
 
VIA TELECOPY
 
Mr. Burton A. Dole Jr.
President
Puritan-Bennett Corporation
9401 Indian Creek Parkway
Overland Park, Kansas 66225
 
Dear Burton:
 
  It has been nearly two weeks since we proposed a merger of our two companies
in which the shareholders of Puritan-Bennett would receive $24 in cash per
share. I attempted to call you today and was informed that you were traveling.
To date, we have received no response from you other than a brief letter
indicating that your Board would consider our proposal "in the near future,"
and requesting that we provide you with additional written terms of our
proposal. We do not understand how your Board can have failed to fully evaluate
and reach a conclusion regarding our proposal over this 12-day period. Further,
your request for
 
                                       20
<PAGE>
 
written terms is unrealistic given your refusal to engage in any discussion
regarding price. Our position has always been that a meeting is necessary to
fully discuss each party's position on all relevant issues.
 
  We have attempted without success for over one month to initiate a dialogue
regarding a merger of our two companies. We have demonstrated our seriousness
and sincerity by proposing an all cash merger that would provide your
shareholders with a substantial premium over recent market prices for Puritan-
Bennett's common stock. We have raised our initial offer substantially in order
to address the concerns of your Board regarding the adequacy of our original
proposal. At all times we have stressed our desire to enter into a negotiated
transaction. Despite our efforts, you have been slow to respond to our proposal
and unwilling to negotiate with us in person.
 
  Given your failure to respond to us in a timely or substantive manner, we can
only conclude that you have not taken Thermo Electron's proposal seriously.
Reluctantly, we are forced to take the only step that we believe is likely to
cause you to give appropriate weight and consideration to our proposal. On
Tuesday, October 25 we will commence a cash tender offer at $24.50 per share
for all of the outstanding Puritan-Bennett common stock.
 
  This is an unprecedented action in our company's history, and one which we
take only after serious deliberation. Our preference continues to be for a
negotiated transaction. However, we believe that we now have no choice but to
present our proposal directly to the Puritan-Bennett shareholders. We of course
remain willing to meet with you at any time to discuss a negotiated merger
agreement.
 
                                          Sincerely,
 
                                          /s/ George
 
                                          George N. Hatsopoulos
                                          Chairman of the Board and
                                           Chief Executive Officer
 
  The Parent then issued a press release announcing that it would commence a
cash tender offer for the shares at $24.50 per share on October 25, 1994.
 
  11. PURPOSE OF THE OFFER; THE MERGER; PLANS FOR THE COMPANY. The purpose of
the Offer and the Merger is to acquire control of, and the entire equity
interest in, the Company. As soon as practicable following consummation of the
Offer, the Purchaser intends to seek the maximum representation obtainable on
the Company's Board of Directors.
 
  The Parent has requested the opportunity to meet with the Company on several
occasions in order to negotiate a merger agreement with the Company. Although
the Company has sent a letter to the Parent requesting additional information
concerning the Parent's merger proposal, the Company has refused to meet in
person with the Parent to negotiate a merger agreement. As a result, the Parent
determined to commence the Offer. See Section 10. The Parent intends to
continue to seek to meet with the Company in order to negotiate a merger
agreement. However, there can be no assurance that the Company will agree to
meet with the Parent for such purpose or, if such negotiations do commence, as
to the outcome thereof. The Parent and the Purchaser reserve the right to amend
or terminate the Offer if the Company should agree to enter into a merger
agreement with the Parent and the Purchaser. The Parent believes that the Offer
provides the Company's shareholders with a method of expressing to the Board of
Directors of the Company that they wish to be able to accept the Offer and to
approve the Merger or a similar transaction with the Parent and the Purchaser.
 
                                       21
<PAGE>
 
  The Merger. The Purchaser intends that, as soon as practicable following
consummation of the Offer, if the Rights Condition, the Section 203 Condition
and the Supermajority Voting Condition have been satisfied, the Purchaser will
propose and seek to have the Company consummate the Merger. The Purchaser
intends that in the Merger, (i) each then outstanding Share not owned by the
Parent, the Purchaser or any other direct or indirect wholly owned subsidiary
of the Parent (other than those Shares held in the treasury of the Company or
Dissenting Shares (as hereinafter defined)) will be converted into the right to
receive in cash the same price per Share paid by the Purchaser in the Offer,
without interest, (ii) each then outstanding Share owned by the Parent, the
Purchaser or any other direct or indirect wholly owned subsidiary of the Parent
and Shares held in the treasury of the Company will be cancelled and (iii) the
shares of Common Stock of the Purchaser will become the shares of common stock
of the Company, which will be the surviving corporation in the Merger.
 
  Required Vote and Certain Provisions of the Company's Articles and By-
Laws. Subject to the provisions of Section 203 of the DGCL described below, the
DGCL provides that, if a corporation owns 90% or more of the outstanding shares
of each class of securities of another corporation, the corporation holding
such stock ownership may merge such other corporation into itself, or itself
into such other corporation, without any action or vote on the part of the
board of directors or shareholders of such other corporation. If after
consummation of the Offer the Purchaser beneficially owned 90% or more of the
outstanding Shares, these "short form" merger provisions of the DGCL would
permit the Purchaser to consummate the Merger without any action or vote by the
Company's Board of Directors and without the vote of any other of the Company's
shareholders. If a "short form" merger is available, subject to satisfaction of
the Rights Condition and the Section 203 Condition, the Purchaser intends to
consummate a "short form" merger in order to effect the Merger.
 
  If the "short form" merger provisions of the DGCL are not applicable to the
Merger, under the DGCL the Merger would generally require the approval of the
Board of Directors of the Company and the affirmative vote of the holders of at
least a majority of the outstanding Shares (the "Majority Vote"). As described
below, a greater vote may be required under the 66 2/3% Charter Provision.
Pursuant to Article Seventh of the Company's Articles, the Board of Directors
is divided into three classes, with each class elected for a term of three
years and one class elected at the Company's annual meeting of shareholders
each year. Article Seventh further provides that the number of directors at any
time may not be less than five or more than 10, the exact number to be
established only by a resolution adopted by a majority of the Board of
Directors, and that a director of the Company may be removed from office only
for cause. Article Eighth of the Company's Articles denies shareholders the
right to take action by written consent in lieu of a special or annual meeting
of shareholders. Pursuant to Section 3 of Article II of the By-Laws, special
meetings of shareholders may be called only by the Chairman of the Board or the
Secretary at the request in writing of a majority of the Board of Directors.
Under the DGCL, the Company's Articles cannot be amended unless the proposed
amendment is first approved by the Company's Board of Directors. Pursuant to
the Company's Articles, the various provisions of the Company's Articles
described in this paragraph, as well as the 66 2/3% Charter Provision described
below, cannot be amended except upon the affirmative vote of a majority of the
whole Board of Directors and of the holders of at least 66 2/3% of all of the
votes entitled to be cast thereon by the holders of the issued and outstanding
shares of voting stock of the Company. Pursuant to the Company's Articles and
By-Laws, the various provisions of the Company's By-Laws described in this
paragraph cannot be amended except by a vote of the Board of Directors of the
Company or by the affirmative vote of the holders of at least 66 2/3% of all of
the votes entitled to be cast thereon by the holders of the issued and
outstanding shares of voting stock of the Company. As a result of the
provisions described in this paragraph, at least two annual meetings of the
Company's shareholders, absent resignations of directors, would be required to
elect new directors comprising a majority of the Board of Directors.
 
  If, after consummation of the Offer, the Purchaser and its affiliates own at
least a majority of the outstanding Shares, the Purchaser could elect a
majority of the Company's directors (although it might not be able to do so
until the second annual meeting of shareholders thereafter) and, unless a
greater vote is
 
                                       22
<PAGE>
 
required under the 66 2/3% Charter Provision or pursuant to Section 203 of the
DGCL (discussed below), could approve the Merger, in each case without the
affirmative vote of any other shareholder of the Company. See Introduction.
 
  Article Fifth of the Articles provides that, in addition to any affirmative
vote required by applicable law (currently, a Majority Vote), the affirmative
vote of the holders of not less than 66 2/3% of the voting power of all issued
and outstanding shares of voting stock of the Company (voting as a single
class) is required to approve certain business combinations (including mergers)
between the Company and a 5% Stockholder, unless the business combination is
approved and recommended to the shareholders of the Company by the favorable
vote of at least 66 2/3% of the whole Board of Directors of the Company. The
acquisition of in excess of 5% of the outstanding Shares by the Purchaser as a
result of the Offer would make the Purchaser a 5% Stockholder for purposes of
the 66 2/3% Charter Provision. The 66 2/3% Charter Provision will not be
applicable to the Merger if the requisite approval of the Board of Directors of
the Company is obtained, whether prior to or after consummation of the Offer.
Moreover, subject to Section 203 of the DGCL, if the Parent and the Purchaser
own at least 66 2/3% of the Shares, as a result of the Offer or otherwise, they
would be able to approve the Merger pursuant to the 66 2/3% Charter Provision
without the vote of any other shareholder of the Company.
 
  The Purchaser believes that, under the circumstances of the Offer and under
applicable law, the Board of Directors of the Company is obligated by its
fiduciary responsibilities to approve and recommend the Merger to the
shareholders of the Company in order to permit the Offer and the Merger to be
consummated. However, there can be no assurance that the Company's Board of
Directors will do so. The Purchaser is hereby requesting that the Company's
Board of Directors approve and recommend the Merger to the shareholders of the
Company in order to make the 66 2/3% Charter Provision inapplicable to the
Merger.
 
  The Purchaser and the Parent reserve the right to solicit shareholder proxies
for the purpose of electing nominees of the Parent and the Purchaser to the
Company's Board of Directors. The By-Laws generally require that if a
shareholder desires to nominate one or more persons for election as directors
at a meeting of shareholders, such shareholder must provide written notice
thereof to the Company not less than 60 days prior to the meeting. The
Purchaser and the Parent also reserve the right to submit other matters to the
shareholders of the Company for their approval at a meeting of such
shareholders, including without limitation a non-binding resolution instructing
the Board of Directors of the Company to approve the Offer and the Merger.
 
  At such time, if any, as nominees of the Purchaser and the Parent comprised a
majority of the Board of Directors of the Company, such persons would be able,
under the DGCL and the Articles and By-Laws, to cause the Company to take
various of the actions described in this Section 11, including (i) approving
(subject to the requisite shareholder approval) the Merger and amendments to
the Articles, (ii) calling special meetings of shareholders and (iii) assuming
the Purchaser has not become an Acquiring Person (as defined in the Rights
Agreement), redeeming the Rights or otherwise making the Rights inapplicable to
the Merger. Nominees of the Purchaser and the Parent would need to comprise at
least 66 2/3% of the whole Board of Directors of the Company in order to be
able to make the 66 2/3% Charter Provision inapplicable to the Merger.
 
  THIS OFFER DOES NOT CONSTITUTE A SOLICITATION OF A PROXY, CONSENT OR
AUTHORIZATION FOR OR WITH RESPECT TO ANY ANNUAL OR SPECIAL MEETING OF THE
COMPANY'S SHAREHOLDERS OR ANY ACTION IN LIEU THEREOF. ANY SUCH SOLICITATION
WHICH THE PURCHASER OR THE PARENT MAY MAKE WILL BE MADE ONLY PURSUANT TO
SEPARATE PROXY MATERIALS IN COMPLIANCE WITH REQUIREMENTS OF SECTION 14(A) OF
THE EXCHANGE ACT.
 
  The foregoing description of the Articles and the By-Laws is qualified in its
entirety by reference to the text of the Articles and By-Laws, copies of which
have been filed by the Company as exhibits to documents filed with the
Commission and may be obtained in the manner described in Section 7.
 
 
                                       23
<PAGE>
 
  The Rights. The following discussion is based on information contained in the
Form 8-A. Although the Purchaser and the Parent do not have any knowledge that
would indicate that any statements contained herein based upon such document
are untrue, neither the Purchaser nor the Parent assumes any responsibility for
the accuracy or completeness of the information contained in such document, or
for any failure by the Company to disclose events that may have occurred and
may affect the significance or accuracy of any such information but which are
unknown to the Purchaser and the Parent. Accordingly, without limiting the
generality of the foregoing provisions of this paragraph, the descriptions
herein of the Rights and the Rights Agreement are qualified to the extent that
information relating thereto is not publicly available.
 
 
  The Board of Directors of the Company, on May 2, 1989, declared a dividend
distribution of one Right for each outstanding Share to the shareholders of
record at the close of business on May 17, 1989 (the "Record Date"). Except as
described below, each Right entitles the registered holder to purchase from the
Company one-half of one share of Common Stock at a price of $45 per half-share
(or $90 per full share), subject to adjustment (the "Right Purchase Price"). On
May 17, 1989, each shareholder of record received one Right for each Share held
by such shareholder. As long as the Rights are attached to the Shares, the
Company is required under the Rights Agreement to issue one Right for each
Share issued between the Record Date and the Distribution Date, so that all
such Shares will have attached Rights.
 
  Initially, Rights are attached to all outstanding Shares, and no separate
Rights Certificates are distributed. A "Distribution Date" for the Rights will
occur upon the earlier of (i) a public announcement that, without the prior
approval of the Company, a person, entity or group of affiliated or associated
persons (an "Acquiring Person") has acquired, or obtained the right to acquire,
beneficial ownership of securities having 20% or more of the voting power of
all outstanding voting securities of the Company or (ii) 10 days (unless such
date is extended by the Board of Directors) following the commencement of (or a
public announcement of an intention to make) a tender offer or exchange offer,
if, upon consummation thereof, the person, entity or group proposing such offer
would become an Acquiring Person.
 
  Until the Distribution Date, the Rights will be represented by and
transferred with and only with Share Certificates and until the Distribution
Date (or earlier redemption or expiration of the Rights), new Share
Certificates issued after May 17, 1989 upon transfer or new issuance of Shares
will contain a notation incorporating the Rights Agreement by reference. Until
the Distribution Date (or earlier redemption or expiration of the Rights), the
surrender for transfer of any Share Certificate will also constitute the
transfer of the Rights associated with the Shares represented by such Share
Certificate.
 
  As soon as practicable following the Distribution Date, separate Rights
Certificates will be mailed to holders of record of Shares as of the close of
business on the Distribution Date. After the Distribution Date, such separate
Rights Certificates alone will represent the Rights.
 
  The Rights are not exercisable in whole or in part at any time until after
the Distribution Date. The Rights will expire on the earliest of (i) May 1,
1999, (ii) the consummation of a merger transaction with a person or group who
acquired Shares pursuant to a Permitted Offer (as defined below), and is
offering in the merger the same price per share and form of consideration paid
in the Permitted Offer, or (iii) the redemption of the Rights by the Company as
described below.
 
  In the event that, after the first date of public announcement that an
Acquiring Person has become such, the Company is involved in a merger or other
business combination transaction in which the Shares are exchanged or changed,
or 50% or more of the Company's assets or earning power are sold (in one or
more transactions), proper provision shall be made so that each holder of a
Right shall thereafter have the right to receive, upon the exercise thereof at
the then current Right Purchase Price multiplied by the then current number of
Shares for which a Right is then exercisable (the product being referred to as
the "Right Exercise Price"), that number of shares of common stock of the
acquiring company (or, in the event that there is more than one acquiring
company, the acquiring company receiving the greatest portion of the assets or
 
                                       24
<PAGE>
 
earning power transferred), which at the time of such transaction would have a
market value of two times the Right Exercise Price (such right being referred
to as the "Merger Right"). Notwithstanding the foregoing, the Merger Right is
inapplicable to a merger of the nature described in clause (ii) of the previous
paragraph.
 
  In the event that a person becomes an Acquiring Person (unless pursuant to a
tender offer or exchange offer for all outstanding Shares at a price and on
terms determined by at least a majority of the Company's Directors who are
neither Acquiring Persons nor affiliates or associates of any Acquiring Person
nor officers of the Company to be both adequate and otherwise in the best
interests of the Company and its shareholders (a "Permitted Offer")), proper
provision shall be made so that each holder of a Right will, for a 60-day
period after the later of any such event and the effective date of an
appropriate registration statement with respect to the securities purchasable
upon exercise of the Rights, have the right to receive upon exercise of the
Right, and payment of the Right Exercise Price, that number of Shares having a
market value of two times the Right Exercise Price, subject to the availability
of a sufficient number of authorized but unissued shares (such right being
referred to as the "Subscription Right"). The holder of a Right will continue
to have the Merger Right whether or not such holder exercises the Subscription
Right.
 
  Upon the occurrence of any of the events giving rise to the exercisability of
the Subscription Right or the Merger Right, any rights that are or were at any
time owned by an Acquiring Person on or after the time the Acquiring Person
became such, shall become void insofar as they relate to the Subscription Right
or the Merger Right.
 
  The Right Purchase Price payable, and the number of Shares or other
securities or property issuable, upon exercise of the Rights are subject to
adjustment from time to time to prevent dilution (i) in the event of a stock
dividend on, or a subdivision, combination or reclassification of the Shares,
(ii) upon the grant to holders of the Shares of certain rights or warrants to
subscribe for Shares, convertible securities or other securities having the
same or more favorable rights, privileges and preferences as the Shares at less
than the current market price of the Shares or (iii) upon the distribution to
holders of the Shares of evidences of indebtedness, cash (other than a regular
quarterly cash dividend out of the earnings or retained earnings of the
Company), assets (other than a dividend payable in Shares) or subscription
rights or warrants (other than those referred to above).
 
  At any time prior to the earlier to occur of (i) a person becoming an
Acquiring Person, or (ii) the expiration of the Rights, the Company may redeem
the Rights in whole, but not in part, at a price of $.01 per Right (the
"Redemption Price"), which redemption shall be effective upon the action of the
Company's Board of Directors. Additionally, the Company may thereafter redeem
the then outstanding Rights in whole, but not in part, at the Redemption Price,
provided that such redemption (i) is made in connection with a merger or other
business combination transaction or series of transactions involving the
Company, but not involving an Acquiring Person or any person who was an
Acquiring Person or (ii) follows the occurrence of an event giving rise to, and
the expiration of the exercise period for, the Subscription Right if and for as
long as an Acquiring Person beneficially owns securities representing less than
20% of the Common Stock. The redemption of Rights described in the preceding
sentence shall be effective only as of such time when the Subscription Right is
not exercisable, and in any event, only after 10 business days' prior notice.
Upon the effective date of the redemption of the Rights, the right to exercise
the Rights will terminate and the only right of the holders of Rights will be
to receive the Redemption Price.
 
  Until a Right is exercised, it will not entitle the holder thereof to any
rights as a shareholder of the Company (other than those of an existing
shareholder), including, without limitation, the right to vote or to receive
dividends. The terms of the Rights may be amended by the Board of Directors of
the Company, but following the Distribution Date no amendment may be made which
adversely affects the interests of holders of the Rights.
 
  The Purchaser believes that, under the Rights Agreement, as a result of the
commencement of the Offer, the Distribution Date will be as early as November
3, 1994, unless prior to such date the Company's Board
 
                                       25
<PAGE>
 
of Directors redeems the Rights or takes action to delay the Distribution Date.
The Purchaser believes that the consummation of the Offer likely would trigger
the exercisability of certain provisions of the Rights, including the
Subscription Right, and, as a result, cause significant dilution to the
Purchaser's interest in the Company and render the Offer and the Merger
economically unattractive for the Purchaser.
 
  Unless, on or before the Expiration Date, the Rights have been redeemed by
the Company's Board of Directors, holders of Shares will be required to tender
one Right for each Share tendered in order to effect a valid tender of such
Share. If separate certificates for the Rights are not issued, a tender of
Shares will also constitute a tender of associated Rights. See Section 3.
 
  The Purchaser believes that, under the circumstances of the Offer and under
applicable law, the Board of Directors of the Company is obligated by its
fiduciary responsibilities to redeem the Rights or to approve the Offer and
determine that the Offer is adequate and in the best interests of the Company
and its shareholders (following which approval and determination the key
unfavorable provisions of the Rights would be inapplicable to the Offer and the
Merger) in order to permit the Offer and the Merger to be consummated. However,
there can be no assurance that the Company's Board of Directors will do so. The
Purchaser is hereby requesting that the Company's Board of Directors redeem the
Rights or approve the Offer and make such determination.
 
  Section 203. Section 203 of the DGCL may have the effect of significantly
delaying the Purchaser's ability to acquire the entire equity interest in the
Company. In general, Section 203 prevents an "Interested Stockholder" (defined
generally as any person that directly or indirectly beneficially owns 15% or
more of a corporation's outstanding voting stock), or any affiliate of an
Interested Stockholder, from engaging in a "Business Combination" (defined to
include a variety of transactions, including mergers) with a Delaware
corporation for three years following the date that such person became an
Interested Stockholder, unless (i) prior to the date such person became an
Interested Stockholder, the board of directors of the corporation approved
either the Business Combination or the transaction which resulted in the person
becoming an Interested Stockholder, (ii) upon consummation of the transaction
which resulted in the person becoming an Interested Stockholder, the Interested
Stockholder owned at least 85% of the voting stock of the corporation
outstanding at the time the transaction commenced (excluding stock held by
directors who are also officers of the corporation and by employee stock plans
in which employee participants do not have the right to determine
confidentially whether shares held subject to the plan will be tendered in a
tender or exchange offer), or (iii) on or subsequent to the date the Interested
Stockholder became such, the Business Combination is (a) approved by the board
of directors of the corporation and (b) authorized at an annual or special
meeting of shareholders, and not by written consent, by the affirmative vote of
the holders of at least 66 2/3% of the outstanding voting stock of the
corporation which is not owned by the Interested Stockholder.
 
  The Purchaser believes that the Section 203 Condition would be satisfied if
the Board of Directors of the Company approved the Offer and the Merger prior
to consummation of the Offer, or if, upon consummation of the Offer, the
Purchaser owned at least 85% of the total voting stock of the Company
outstanding at the time the transaction commenced (excluding Shares owned by
persons who are directors and also officers of the Company), or if the
Purchaser, in its sole discretion, were satisfied that Section 203 was
inapplicable to the Merger for any reason, including, without limitation, those
specified in Section 203.
 
  The Purchaser believes that, under the circumstances of the Offer and under
applicable law, the Board of Directors of the Company is obligated by its
fiduciary responsibilities to approve, pursuant to Section 203, the acquisition
of Shares pursuant to the Offer and the Merger. However, there can be no
assurance that the Company's Board of Directors will do so. The Purchaser is
hereby requesting that the Company's Board of Directors approve the Offer and
the Merger for purposes of Section 203.
 
  Appraisal Rights in Connection with the Merger. No appraisal rights are
available in connection with the Offer. However, if the Merger is consummated,
shareholders of the Company will have certain rights
 
                                       26
<PAGE>
 
under Section 262 of the DGCL to dissent and demand appraisal of, and payment
in cash of the fair value of, their Shares ("Dissenters' Shares"). Such rights,
if the statutory procedures were complied with, could lead to a judicial
determination of the fair value (excluding any element of value arising from
the accomplishment or expectation of the Merger) required to be paid in cash to
such dissenting holders for their Shares. Any such judicial determination of
the fair value of Shares could be based upon consideration other than, or in
addition to, the price paid in the Offer and the market value of the Shares,
including asset values and the investment value of the Shares. The value so
determined could be more or less than the purchase price per Share pursuant to
the Offer or the consideration per Share to be paid in the Merger.
 
  In addition, several decisions by Delaware courts have held that, in certain
instances, a controlling shareholder of a corporation involved in a merger has
a fiduciary duty to the other shareholders that requires the merger to be fair
to such other shareholders. In determining whether a merger is fair to minority
shareholders, the Delaware courts have considered, among other things, the type
and amount of consideration to be received by the shareholders and whether
there were fair dealings among the parties. The Delaware Supreme Court has
indicated in recent decisions that in most cases the remedy available in a
merger that is found not to be "fair" to minority shareholders is the right to
appraisal described above or a damages remedy based on essentially the same
principles.
 
  Rule 13e-3. The Commission has adopted Rule 13e-3 under the Exchange Act
which is applicable to certain "going private" transactions and which may,
under certain circumstances, be applicable to the Merger following the purchase
of Shares pursuant to the Offer in which the Purchaser seeks to acquire any
remaining Shares. Rule 13e-3 should not be applicable to the Merger if the
Merger is consummated within one year after the expiration or termination of
the Offer and the price paid in the Merger is not less than the per Share price
paid pursuant to the Offer. However, in the event that the Purchaser is deemed
to have acquired control of the Company pursuant to the Offer and if the Merger
is consummated more than one year after completion of the Offer or an
alternative acquisition transaction is effected whereby shareholders of the
Company receive consideration less than that paid pursuant to the Offer, in
either case at a time when the Shares are still registered under the Exchange
Act, the Purchaser may be required to comply with Rule 13e-3 under the Exchange
Act. If applicable, Rule 13e-3 would require, among other things, that certain
financial information concerning the Company, and certain information relating
to the fairness of the Merger or such alternative transaction and the
consideration offered to minority shareholders in the Merger or such
alternative transaction, be filed with the Commission and disclosed to
shareholders prior to consummation of the Merger or such alternative
transaction. The purchase of a substantial number of Shares pursuant to the
Offer may result in the Company being able to terminate its Exchange Act
registration. See Section 13. If such registration were terminated, Rule 13e-3
would be inapplicable to the Merger or any such future alternative transaction.
 
  Other. The exact timing and details of the Merger will depend on a variety of
factors and legal requirements, the actions of the Company's Board of
Directors, the number of Shares acquired by the Purchaser pursuant to the Offer
and whether the Rights Condition, the Section 203 Condition and the
Supermajority Voting Condition are satisfied or waived. Satisfaction of one or
more of the foregoing conditions will require the approval of the Offer and the
Merger by the Board of Directors of the Company. Although the Purchaser has
proposed the Merger to the Company and plans to seek to have the Company
consummate the Merger as soon as practicable after consummation of the Offer,
the Purchaser can give no assurance that the Merger will be consummated or as
to the timing of the Merger if it is consummated. Although the Purchaser has
proposed the Merger on the terms described above, it is possible that, as a
result of substantial delays in the Purchaser's ability to effect the Merger,
information hereafter obtained by the Purchaser, changes in general economic or
market conditions or in the business, operations or financial condition or
prospects of the Company, any of the Rights Condition, the Section 203
Condition or the Supermajority Voting Condition not being satisfied or any
other currently unforeseen factors, the Merger may not be so proposed, may be
delayed or abandoned or may be proposed on different terms. Although it
 
                                       27
<PAGE>
 
has no current intention to do so, the Purchaser expressly reserves the right
to propose a Merger on terms other than those described above and the right to
withdraw any Merger proposal.
 
  The Purchaser reserves the right to purchase, following consummation or
termination of the Offer, additional Shares or Rights in the open market, in
privately negotiated transactions, in another tender offer or exchange offer or
otherwise. In addition, in the event that the Purchaser decides not to propose
the Merger, to propose a Merger on terms other than those described above or to
withdraw any Merger previously proposed, the Purchaser will evaluate its other
alternatives. Such alternatives could include purchasing additional Shares or
Rights in the open market, in privately negotiated transactions, in another
tender offer or exchange offer or otherwise, or taking no further action to
acquire additional Shares or Rights. Any additional purchases of Shares or
Rights could be at a price greater or less than the price to be paid for Shares
and Rights in the Offer and could be for cash or other consideration.
Alternatively, the Purchaser and the Parent may sell or otherwise dispose of
any or all Shares or Rights acquired pursuant to the Offer or otherwise. Such
transactions may be effected on terms and at prices then determined by the
Purchaser and the Parent, which may vary from the price paid for Shares and
Rights in the Offer.
 
  Plans for the Company. In connection with the Offer, the Parent and the
Purchaser have reviewed, and will continue to review, on the basis of publicly
available information, various possible business strategies involving the
Company and its operations that they might consider in the event that they
acquire control of the Company. If and to the extent the Parent and the
Purchaser acquire control of the Company or otherwise obtain access to the
books and records of the Company, the Parent and the Purchaser intend to
conduct a detailed review of the Company and its assets, businesses, labor
practices, operations, properties, dividend policy and other policies,
corporate structure, capitalization and management and personnel and may on the
basis of such review propose or seek to effect changes or transactions with
respect to or affecting any of such matters. Any transaction might involve the
Parent or a wholly or partially owned subsidiary of the Parent. It is the
Parent's current intention to seek to cause the Company to eliminate dividend
payments on the Shares following consummation of the Offer.
 
  Except as described in this Offer to Purchase, none of the Purchaser, the
Parent nor, to the best knowledge of the Purchaser and the Parent, any of the
persons listed on Schedule I have any present plans or proposals that would
relate to or result in an extraordinary corporate transaction such as a merger,
reorganization or liquidation involving the Company or any of its subsidiaries,
a sale or other transfer of a material amount of assets of the Company or any
of its subsidiaries, any material change in the capitalization or dividend
policy of the Company or any other material change in the Company's corporate
structure or business or the composition of its Board of Directors or
management.
 
  12. DIVIDENDS AND DISTRIBUTIONS. If, on or after October 24, 1994, the
Company should split, combine or otherwise change the Shares or its
capitalization or shall disclose that it has taken any such action, then,
without prejudice to the Purchaser's rights described in Section 14, the
Purchaser may, in its sole discretion, make such adjustments to the purchase
price and other terms of the Offer, including without limitation, the number or
type of securities offered to be purchased, as it deems appropriate to reflect
such split, combination or other change.
 
  If, on or after October 24, 1994, the Company should declare or pay any cash
or stock dividend or other distribution on, or issue any rights with respect
to, the Shares (other than regular quarterly cash dividends not in excess of
$.03 per Share, having customary and usual record and payment dates) that is
payable or distributable to shareholders of record on a date prior to the
transfer to the name of the Purchaser or the nominee or transferee of the
Purchaser on the Company's stock transfer records of such Shares that are
purchased pursuant to the Offer (except that if the Rights are redeemed by the
Company's Board of Directors in accordance with the terms of the Rights
Agreement, tendering shareholders who are holders of record as of the
applicable record date will be entitled to receive and retain the redemption
price of $.01 per Right in accordance with the Rights Agreement), then, without
prejudice to the Purchaser's rights described in Section 14, (i) the purchase
price per Share payable by the Purchaser pursuant to the Offer will be reduced
to the extent any such dividend or distribution is payable in cash and (ii) any
non-cash dividend, distribution
 
                                       28
<PAGE>
 
(including additional Shares) or right received and held by a tendering
shareholder shall be received and held by the tendering shareholder for the
account of the Purchaser and will be required to be promptly remitted and
transferred by the tendering shareholder to the Depositary for the account of
the Purchaser, accompanied by appropriate documentation of transfer. Pending
such remittance or appropriate assurance thereof, the Purchaser will be,
subject to applicable law, entitled to all rights and privileges as owner of
any such non-cash dividend, distribution or right and may withhold the entire
purchase price or deduct from the purchase price the amount or value thereof,
as determined by the Purchaser in its sole discretion.
 
  13. POSSIBLE EFFECTS OF THE OFFER ON THE MARKET FOR THE SHARES, NNM QUOTATION
AND EXCHANGE ACT REGISTRATION.
 
  Possible Effects of the Offer on the Market for the Shares. The purchase of
Shares by the Purchaser pursuant to the Offer or following the consummation of
the Offer will reduce the number of Shares that might otherwise trade publicly
and will reduce the number of holders of Shares. This could adversely affect
the liquidity and market value of the remaining Shares held by the public.
 
  NNM Quotation. Depending upon the aggregate market value and the number of
Shares not purchased pursuant to the Offer, as well as the identity of the
holders of such Shares, the Shares may no longer meet the quantitative
requirements of the National Association of Securities Dealers, Inc. (the
"NASD") for continued inclusion in the NNM, which require that an issuer have
at least 200,000 publicly held shares, held by at least 400 shareholders or 300
shareholders of round lots, with a market value of at least $1 million, have
net tangible assets of at least $1 million, $2 million or $4 million (depending
on profitability levels during the issuer's four most recent fiscal years) and
have a minimum bid price per Share of $1 (unless the issuer has a public float
of at least $3 million and at least $4 million of net tangible assets).
 
  In the event that the Shares no longer meet the requirements for NNM
quotation, it is possible that the Shares would continue to trade in the over-
the-counter market and that price or other quotations might still be available
from other sources. The extent of the public market for the Shares and the
availability of such quotations would, however, depend upon such factors as the
number of holders and/or the aggregate market value of such Shares remaining at
such time, the interest in maintaining a market in such Shares on the part of
securities firms, the possible termination of registration of such Shares under
the Exchange Act, as described below, and other factors. The Purchaser cannot
predict whether a reduction in the number of Shares that might otherwise trade
publicly would have an adverse or beneficial effect on the market price for or
marketability of the Shares or whether it would cause future market prices to
be greater or less than the price paid in the Offer.
 
  Exchange Act Registration. The Shares are currently registered under the
Exchange Act. The purchase of Shares pursuant to the Offer or following
consummation of the Offer may result in the Shares becoming eligible for
deregistration under the Exchange Act. Registration of the Shares may be
terminated upon application of the Company to the Commission if the Shares are
not listed on a national securities exchange and there are fewer than 300
record holders of the Shares. The termination of the registration of the Shares
under the Exchange Act, assuming there are no other securities of the Company
subject to registration, would substantially reduce the information required to
be furnished by the Company to holders of the Shares and would make certain
provisions of the Exchange Act, such as the short-swing profit recovery
provisions of Section 16(b), the requirement of furnishing a proxy statement in
connection with shareholders' meetings pursuant to Section 14(a) and the
requirements of Rule 13e-3 under the Exchange Act with respect to "going
private" transactions, no longer applicable to the Shares. Furthermore,
"affiliates" of the Company and persons holding "restricted securities" of the
Company may be deprived of the ability to dispose of the securities pursuant to
Rule 144 under the Securities Act of 1933, as amended. If registration of the
Shares under the Exchange Act were terminated, the Shares would no longer be
"margin securities" or eligible for NNM quotation. The Purchaser presently
intends to seek to cause the Company to terminate the registration of the
Shares under the Exchange Act as soon after the consummation of the Offer or
Merger as the requirements for termination of registration are met.
 
                                       29
<PAGE>
 
  Margin Regulations. The Shares are currently "margin securities" under the
rules of the Board of Governors of the Federal Reserve System (the "Federal
Reserve Board"), which has the effect, among other things, of allowing brokers
to extend credit on the collateral of such Shares for the purpose of buying,
carrying, or trading in securities ("purpose loans"). Depending upon factors
such as the number of record holders of the Shares and the number and market
value of publicly held Shares, following the purchase of Shares pursuant to
this Offer or following consummation of this Offer, the Shares might no longer
constitute "margin securities" for purposes of the Federal Reserve Board's
margin regulations and therefore could no longer be used as collateral for
purpose loans made by brokers. In addition, if registration of the Shares under
the Exchange Act were terminated, the Shares would no longer constitute "margin
securities".
 
  Based on publicly available information, the Purchaser believes the Rights
are attached to the Shares and are not separately transferable. As a result of
the commencement of the Offer, the Distribution Date may be as early as
November 3, 1994. The Purchaser expects that, as soon as practicable after the
Distribution Date, Rights Certificates will be sent to all holders of Rights
and the Rights will separate from the Shares. If the Distribution Date occurs
and the Rights separate from the Shares, the foregoing discussion with respect
to the effect of the Offer on the market for the Shares, NNM quotation (if
applicable) and Exchange Act registration would apply to the Rights in a
similar manner.
 
  14. CERTAIN CONDITIONS OF THE OFFER. Notwithstanding any other provision of
the Offer, and in addition to, (and not in limitation of), the Purchaser's
rights to extend or amend the Offer in any respect at any time in its sole
discretion, the Purchaser shall not be required to accept for payment or,
subject to any applicable rules and regulations of the Commission, including
Rule 14e-1(c) under the Exchange Act (relating to the Purchaser's obligation to
pay for or return tendered Shares promptly after expiration, termination or
withdrawal of the Offer), to pay for any Shares or Rights tendered pursuant to
the Offer, and may postpone the acceptance for payment or, subject to the
restriction referred to above, payment for any Shares or Rights tendered
pursuant to the Offer, and may amend or terminate the Offer (whether or not any
Shares have theretofore been purchased or paid for) if, in the sole judgment of
the Purchaser (i) any one or more of the Minimum Condition, the Rights
Condition, the Section 203 Condition and/or the Supermajority Voting Condition
shall not have been satisfied or (ii) at any time on or after October 24, 1994
and prior to the acceptance for payment of, or payment for, Shares, any one or
more of the events listed below shall have occurred or shall be deemed by the
Parent or the Purchaser to have occurred:
 
    (a) there shall have been threatened, instituted or pending any action,
  proceeding, application, claim or counterclaim by or before any court or
  governmental, regulatory or administrative agency, authority or tribunal,
  domestic, foreign or supranational (other than actions, proceedings,
  applications, claims or counterclaims filed or initiated by the Parent or
  the Purchaser) which (i) seeks to challenge the acquisition by the
  Purchaser of the Company or the Shares or Rights, restrain, prohibit or
  delay the making or consummation of the Offer or the Merger or any other
  merger or business combination involving the Purchaser or any of its
  affiliates and the Company or any of its subsidiaries, prohibit the
  performance of any of the contracts or other arrangements entered into by
  the Purchaser or any of its affiliates in connection with the acquisition
  of the Company or the Shares or Rights, or obtain any damages in connection
  with any of the foregoing, (ii) seeks to make the purchase of, or payment
  for, some or all of the Shares or Rights pursuant to the Offer, the Merger
  or otherwise, illegal, (iii) seeks to impose limitations on the ability of
  the Purchaser or the Company or any of their respective affiliates or
  subsidiaries effectively to acquire or hold, or requiring the Purchaser,
  the Company or any of their respective affiliates or subsidiaries to
  dispose of or hold separate, any portion of the assets or the business of
  the Purchaser or its affiliates or the Company or its subsidiaries, or
  impose limitations on the ability of the Purchaser, the Company or any of
  their respective affiliates or subsidiaries to continue to conduct, own or
  operate all or any portion of their businesses and assets as heretofore
  conducted, owned or operated, (iv) seeks to impose or may result in
  limitations on the ability of the Purchaser or any of its affiliates to
  exercise full rights of ownership of the Shares or Rights purchased by
  them, including, but not limited to, the right to vote the Shares purchased
  by them on all matters properly presented to the shareholders of the
  Company, or the right to vote any shares of capital stock of any subsidiary
  directly
 
                                       30
<PAGE>
 
  or indirectly owned by the Company, (v) may, in the sole judgment of the
  Purchaser, result in a material diminution in the benefits expected to be
  derived by the Purchaser or the Parent as a result of the transactions
  contemplated by the Offer, including the Merger, or the value of the Shares
  to the Purchaser or (vi) seeks to impose voting, procedural, price or other
  requirements in addition to those under the DGCL and federal securities
  laws (each as in effect on the date of this Offer to Purchase) or any
  material condition to the Offer that is unacceptable to the Purchaser, or
  (vii) otherwise directly or indirectly relates to the Offer, the Merger or
  any other business combination with the Company or which otherwise, in the
  sole judgment of the Parent or the Purchaser, might adversely affect the
  Company or any of its subsidiaries or affiliates, or the Parent, the
  Purchaser or any of their respective affiliates or subsidiaries or the
  value of the Shares; or
 
    (b) other than the routine application of the waiting period provisions
  under the HSR Act, and the necessity for the approvals and other actions by
  any domestic (federal and state), foreign or supranational governmental,
  administrative or regulatory agency, authority or tribunal described in
  paragraph (h) below, there shall have been proposed, sought, promulgated,
  enacted, entered, enforced, amended, issued or deemed applicable to (x) the
  Offer, the Merger or any other business combination involving the Company
  or (y) the Company, the Purchaser, the Parent, or any of their respective
  subsidiaries or affiliates, by any government or governmental, regulatory
  or administrative agency or authority or by any court or tribunal, in each
  case whether domestic, foreign or supranational, any statute, rule,
  regulation, interpretation, judgment, decree, decision, order or injunction
  that, in the sole judgment of the Purchaser, might, directly or indirectly,
  result in any of the consequences referred to in clauses (i) through (vii)
  of paragraph (a) above; or
 
    (c) any change (or any condition, event or development involving a
  prospective change) shall have occurred or been threatened in the business,
  properties, assets, liabilities, shareholders' equity, condition (financial
  or otherwise), capitalization, licenses, franchises, permits, permit
  applications, operations, results of operations, performance or prospects
  of the Company or any of its subsidiaries or affiliates (or the Purchaser
  shall have become aware thereof) or in general economic or financial market
  conditions in the United States or abroad that, in the sole judgment of the
  Purchaser, is or may be materially adverse to the Company or any of its
  subsidiaries or affiliates, or the market price of, or trading in, the
  Shares, or the Purchaser shall have become aware of any facts that, in the
  sole judgment of the Purchaser, have or may have material adverse
  significance with respect to either the value of the Company or any of its
  subsidiaries or affiliates or the value of the Shares to the Purchaser or
  any of its affiliates; or
 
    (d) there shall have occurred (i) any general suspension of trading in,
  or limitation on prices for, securities on any national securities exchange
  or in the United States over-the-counter market, (ii) the declaration of a
  banking moratorium or any suspension of payments in respect of banks in the
  United States, (iii) any material adverse change (or any existing or
  threatened condition, event or development involving a prospective material
  adverse change) in United States or any other currency exchange rates or a
  suspension of, or a limitation on, the markets therefor, (iv) any other
  material adverse change in the market price of the Shares or in the
  securities or financial markets in the United States or abroad, including,
  without limitation, a decline of at least 15% in either the Dow Jones
  Average of Industrial Stocks or the Standard & Poor's 500 Index from that
  existing at the close of business on October 24, 1994 through the date of
  termination or expiration of the Offer, (v) the commencement of a war,
  armed hostilities or other national or international calamity directly or
  indirectly involving the United States, (vi) any limitation (whether or not
  mandatory) imposed by any governmental authority or agency on, or any other
  event that, in the sole judgment of the Purchaser, may have material
  adverse significance with respect to the extension of credit by banks or
  other lending institutions or (vii) in the case of any of the situations
  described in clauses (i) through (vi) above existing at the time of the
  commencement of the Offer, in the sole judgment of the Purchaser, a
  material acceleration or worsening thereof; or
 
    (e) a tender or exchange offer for some or all of any outstanding
  securities of the Company or any of its subsidiaries (including the Shares
  or Rights) shall have been publicly proposed to be made or shall have been
  made by another person (including the Company or any of its subsidiaries or
  affiliates), or it
 
                                       31
<PAGE>
 
  shall have been publicly disclosed or the Purchaser shall have otherwise
  learned that (i) any person, entity (including the Company or any of its
  subsidiaries or affiliates) or "group" (within the meaning of Section
  13(d)(3) of the Exchange Act) shall have acquired or proposed to acquire
  beneficial ownership of more than 5% of any class or series of capital
  stock of the Company (including the Shares or Rights) through the
  acquisition of stock, the formation of a group or otherwise, or shall have
  been granted any option, right or warrant, conditional or otherwise, to
  acquire beneficial ownership of more than 5% of any class or series of
  capital stock of the Company (including the Shares or Rights) other than
  acquisitions for bona fide arbitrage purposes only and other than as
  disclosed in a Schedule 13D or 13G on file with the Commission prior to
  October 24, 1994, (ii) any such person, entity or group which, prior to
  October 24, 1994, had filed such a Schedule with the Commission, shall have
  acquired or proposed to acquire, through the acquisition of stock, the
  formation of a group or otherwise, beneficial ownership of additional
  shares of any class or series of capital stock of the Company (including
  the Shares or Rights) constituting 1% or more of any such class or series,
  or shall have been granted any option, right or warrant, conditional or
  otherwise, to acquire beneficial ownership of shares of any class or series
  of capital stock of the Company (including the Shares or Rights)
  constituting 1% or more of any such class or series, (iii) any person,
  entity or group shall have entered into a definitive agreement or an
  agreement in principle or made a proposal with respect to a tender or
  exchange offer for some or all the Shares or Rights or a merger,
  consolidation or other business combination with or involving the Company
  or any of its subsidiaries or (iv) any person, entity or group shall have
  filed a Premerger Notification and Report Form under the HSR Act or made a
  public announcement reflecting an intent to acquire the Company or any of
  its subsidiaries or any assets or securities of the Company or any of its
  subsidiaries; or
 
    (f) the Company or any of its subsidiaries shall have, directly or
  indirectly, (i) split, combined or otherwise changed, or authorized or
  proposed the split, combination or other change of, the Shares or Rights or
  its capitalization, (ii) acquired or otherwise caused a reduction in the
  number of, or authorized or proposed the acquisition or other reduction in
  the number of, any outstanding Shares or other securities of the Company
  (other than a redemption of the Rights in accordance with the terms of the
  Rights Agreement) or other securities of the Company or any subsidiary
  thereof, (iii) issued, distributed, pledged or sold, or authorized,
  proposed or announced the issuance, distribution, pledge or sale of, (A)
  any additional Shares, shares of any other class or series of capital
  stock, other voting securities, or any securities convertible into or
  exchangeable or exercisable for any of the foregoing, or options, rights or
  warrants, conditional or otherwise, to acquire any of the foregoing, except
  for the issuance of Shares reserved for issuance on or prior to October 24,
  1994 pursuant to the exercise of then outstanding options under the Company
  Option Plans, in accordance with the terms thereof as disclosed in filings
  filed with the Commission on or prior to October 24, 1994 or (B) any other
  securities or rights in respect of, in lieu of or in substitution or
  exchange for any shares of its capital stock, (iv) permitted the issuance
  or sale of any shares of any class of capital stock or other debt or equity
  securities of any subsidiary of the Company or any securities convertible
  into or exchangeable or exercisable for any of the foregoing, (v) declared,
  paid or proposed to declare or pay any dividend or other distribution,
  whether payable in cash, securities or other property, on, or in respect
  of, any Shares (other than regular cash dividends on the Shares at a
  quarterly rate not in excess of $.03 per Share, having customary and usual
  record and payment dates or a distribution of the Rights Certificates in
  accordance with the terms of the Rights Agreement or a redemption of the
  Rights Certificates in accordance with the terms of the Rights Agreement)
  or any other capital stock of the Company, (vi) altered or proposed to
  alter any material term of any outstanding security of the Company or any
  of its subsidiaries (including the Rights), (vii) issued, distributed or
  sold, or authorized or proposed the issuance, distribution or sale of, any
  debt securities or securities convertible into or exchangeable or
  exercisable for debt securities or any rights, warrants or options
  entitling the holder thereof to purchase or otherwise acquire any debt
  securities, or otherwise incurred, authorized or proposed the incurrence
  of, any debt other than in the ordinary course of business and consistent
  with past practice or any debt containing, in the sole judgment of the
  Purchaser, burdensome covenants or security provisions, (viii) authorized,
  recommended, proposed,
 
                                       32
<PAGE>
 
  effected or announced its intention to engage in any merger (other than the
  Merger), consolidation, liquidation, dissolution, business combination,
  change in capitalization, acquisition (including by way of exchange) of
  assets or securities (other than a redemption of the Rights in accordance
  with the terms of the Rights Agreement), disposition (including by way of
  exchange) of assets or securities other than in the ordinary course of
  business, joint venture, any release or relinquishment of any material
  contract or other rights of the Company or any of its affiliates or any
  comparable event not in the ordinary course of business, (ix) authorized,
  recommended, proposed or announced its intention to authorize, recommend or
  propose any arrangement or transaction that, in the sole judgment of the
  Purchaser, has or may have material adverse significance with respect to
  the value of the Company or any of its affiliates, or the value of the
  Shares to the Purchaser or any of its affiliates, (x) amended or proposed,
  adopted or authorized any amendment (other than any amendment which
  provides that the Rights are inapplicable to the Offer and the Merger) to
  the Articles or the By-Laws or similar organizational documents of the
  Company or any of its subsidiaries or the Rights Agreement or the Purchaser
  shall have learned that the Company or any of its subsidiaries shall have
  proposed or adopted any such amendment which shall not have been previously
  disclosed, (xi) entered into or amended any employment, change of control,
  severance or similar agreement, arrangement or plan with or for the benefit
  of any employee, director or consultant of the Company or any of its
  subsidiaries (other than in the ordinary course of business) so as to
  provide for increased or accelerated benefits as a result of or in
  connection with the making of the Offer, the acceptance for payment of or
  payment for Shares and Rights by the Purchaser or the consummation by the
  Purchaser or any of its affiliates of the Merger or any other business
  combination involving the Company, (xii) except as may be required by law,
  taken any action to terminate or amend any employee benefit plan (as
  defined in Section 3(3) of the Employee Retirement Income Security Act of
  1974, as amended) of the Company or any of its affiliates, (xiii) agreed in
  writing or otherwise to take any of the foregoing actions or the Purchaser
  shall have learned about any such action which shall not have been
  previously publicly disclosed by the Company; or
 
    (g) the Purchaser shall become aware (i) that any material contractual
  right of the Company or any of its subsidiaries or affiliates shall be
  impaired or otherwise adversely affected or that any material amount of
  indebtedness of the Company or any of its subsidiaries shall become
  accelerated or otherwise become due or become subject to acceleration prior
  to its stated due date, in each case with or without notice or the lapse of
  time or both, as a result of or in connection with the Offer or the
  consummation by the Purchaser or any of its affiliates of the Merger or any
  other business combination involving the Company, (ii) of any covenant,
  term or condition in any of the instruments or agreements of the Company or
  any of its subsidiaries that, in the sole judgment of the Purchaser, is or
  may be (whether considered alone or in the aggregate with other such
  covenants, terms or conditions) materially adverse to either the value of
  the Company or any of its subsidiaries (including, without limitation, any
  event of default that may occur as a result of or in connection with the
  Offer, the consummation by the Purchaser or any of its affiliates of the
  Merger or any other business combination involving the Company) or the
  value of the Shares to the Purchaser or any of its affiliates or the
  consummation by the Purchaser or any of its affiliates of the Merger or any
  other business combination involving the Company, (iii) that any report,
  document, instrument, financial statement or schedule of the Company filed
  with the Commission contained, when filed, an untrue statement of a
  material fact or omitted to state a material fact required to be stated
  therein or necessary in order to make the statements made therein, in light
  of the circumstances under which they were made, not misleading or (iv)
  that the number of options outstanding under the Company Option Plans is
  materially greater than the number of outstanding options as of January 31,
  1994, that the terms of options granted since January 31, 1994 are
  materially less favorable to the Company than options granted prior to
  January 31, 1994, or that the terms of options outstanding as of January
  31, 1994 have been modified, in the aggregate, in a manner that is
  materially less favorable to the Company than prior to such modification;
  or
 
    (h) any waiting periods under the HSR Act applicable to the purchase of
  Shares pursuant to the Offer shall not have expired or been terminated, or
  any approval, permit, authorization or consent of any domestic or foreign
  or supranational governmental, administrative or regulatory agency
  (federal,
 
                                       33
<PAGE>
 
  state, local, provincial or otherwise) (including those described or
  referred to in Section 15) shall not have been obtained on terms
  satisfactory to the Parent, in its sole discretion; or
 
    (i) the Purchaser or any of its affiliates shall have entered into a
  definitive agreement or announced an agreement in principle with respect to
  the Merger or any other business combination with the Company or any of its
  affiliates or the purchase of any material portion of the securities or
  assets of the Company or any of its subsidiaries or the Purchaser or any of
  its affiliates and the Company shall have agreed that the Purchaser shall
  amend or terminate the Offer or postpone the purchase or payment for the
  Shares pursuant thereto;
 
which, in the sole judgment of the Purchaser with respect to each and every
matter referred to above and regardless of the circumstances (including any
action or inaction by the Purchaser or any of its affiliates) giving rise to
any such condition, makes it inadvisable to proceed with the Offer or with such
acceptance for payment of or payment for Shares and Rights.
 
  The foregoing conditions are for the sole benefit of the Purchaser and may be
asserted by the Purchaser regardless of the circumstances giving rise to any
such condition and may be waived by the Purchaser, in whole or in part, at any
time and from time to time in its sole discretion. Any determination by the
Purchaser concerning the events described above shall be final and binding upon
all parties including tendering shareholders. The failure by the Purchaser at
any time to exercise any of the foregoing rights shall not be deemed a waiver
of any such right and each such right shall be deemed an ongoing right which
may be asserted at any time and from time to time. Satisfaction of one or more
of the Rights Condition, the Section 203 Condition and the Supermajority Voting
Condition will require the approval of the Offer and the Merger by the Board of
Directors of the Company.
 
  A public announcement shall be made of a material change in, or waiver of,
such conditions, to the extent required by Rules 14d-4(c) and 14d-6(d) under
the Exchange Act, and the Offer will be extended in connection with any such
change or waiver to the extent required by such rules.
 
  15. CERTAIN LEGAL MATTERS AND REGULATORY APPROVALS.
 
  General. Except as set forth below, based upon an examination of publicly
available filings by the Company with the Commission, neither the Purchaser nor
the Parent is aware of (i) any licenses or other regulatory permits that appear
to be material to the business of the Company and its subsidiaries, taken as a
whole, that might be adversely affected by the Purchaser's acquisition of
Shares (and the indirect acquisition of the stock of the Company's
subsidiaries) as contemplated herein, or (ii) any material filings, approvals
or other actions by or with any domestic (federal or state), foreign or
supranational governmental, administrative or regulatory agency or authority
that would be required for the acquisition or ownership of Shares (or the
indirect acquisition of the stock of the Company's subsidiaries) by the
Purchaser pursuant to the Offer or the Merger. Should any such approval or
other action be required, it is the Purchaser's present intention to seek such
approval or action. Although the Purchaser does not presently intend to delay
the purchase of Shares tendered pursuant to the Offer pending the receipt of
any such approval or the taking of any such action (subject to the Purchaser's
right to delay or decline to purchase Shares if any of the conditions in
Section 14 shall have occurred), there can be no assurance that any such
approval or other action, if needed, would be obtained without substantial
conditions or that adverse consequences might not result to the business of the
Company, the Parent or the Purchaser or that certain parts of the businesses of
the Company, the Parent or the Purchaser might not have to be disposed of or
held separate or other substantial conditions complied with in order to obtain
such approval or other action or in the event that such approval was not
obtained or such other action was not taken, any of which could cause the
Purchaser to elect to terminate the Offer without the purchase of the Shares
thereunder. The Purchaser's obligation under the Offer to accept for payment
and pay for Shares and Rights is subject to certain conditions, including
conditions relating to the legal matters discussed in this Section 15. See
Section 14.
 
 
                                       34
<PAGE>
 
  Litigation.  On October 7, 1994, Kenneth Steiner, a shareholder of the
Company, filed a class action complaint entitled Kenneth Steiner v. Puritan-
Bennett Corp., Burton A. Dole, Jr., C. Phillip Larson, Jr., Andre F. Marion,
Thomas A. McDonnell, Daniel C. Weary, Frank P. Wilton, C.A. No. 13790, against
the Company and its directors in the Court of Chancery of the State of Delaware
in and for New Castle County alleging, among other things, that the Company's
shareholders have been, and continue to be, deprived of the opportunity to
realize fully the benefits of their investment in the Company as a result of
the directors refusal to properly consider the Parent's offer for the Company,
which actions are alleged to constitute unfair dealing and a breach of
fiduciary duty to maximize shareholder value. As relief, the complaint seeks an
order directing the Company's directors to carry out their fiduciary duties to
the Company's shareholders by announcing their intention to cooperate fully
with the Parent or any other entity having a bona fide interest in proposing
any transactions which would maximize shareholder value, including, but not
limited to, a merger or acquisition of the Company, as well as damages and
costs.
 
  State Takeover Laws. A number of states (including Delaware, where the
Company is incorporated) have adopted takeover laws and regulations which
purport, to varying degrees, to be applicable to attempts to acquire securities
of corporations which are incorporated in such states or which have, or whose
business operations have substantial economic effects in such states, or which
have substantial assets, security holders, principal executive offices or
principal places of business therein. To the extent that certain provisions of
certain of these state takeover statutes purport to apply to the Offer, the
Purchaser believes that such laws conflict with federal law and constitute an
unconstitutional burden on interstate commerce. In 1982, the Supreme Court of
the United States, in Edgar v. Mite Corp., invalidated on constitutional
grounds the Illinois Business Takeovers Act, which, as a matter of state
securities law, made takeovers of corporations meeting certain requirements
more difficult and thus imposed a substantial burden on interstate commerce,
and the reasoning in such decision is likely to apply to certain other state
takeover statutes. In 1987, however, in CTS Corp. v. Dynamics Corp. of America,
the Supreme Court of the United States held that the State of Indiana could, as
a matter of corporate law and, in particular, those aspects of corporate law
concerning corporate governance, constitutionally disqualify a potential
acquiror from voting on the affairs of a target corporation without the
approval of a majority of the disinterested shareholders, provided that such
laws were applicable only under certain conditions. Subsequently, in TLX
Acquisition Corp. v. Telex Corp., a federal district court in Oklahoma ruled
that the Oklahoma takeover statute was unconstitutional insofar as it applied
to corporations incorporated outside Oklahoma in that it would subject such
corporations to inconsistent regulations. Similarly, in Tyson Foods, Inc. v.
McReynolds, a federal district court in Tennessee ruled that four Tennessee
takeover statutes were unconstitutional as applied to corporations incorporated
outside Tennessee. This decision was affirmed by the United States Court of
Appeals for the Sixth Circuit. In December 1988, a federal district court in
Florida held in Grand Metropolitan PLC v. Butterworth that the provisions of
the Florida Affiliated Transactions Act and the Florida Control Share
Acquisition Act were unconstitutional as applied to corporations incorporated
outside of Florida.
 
  The Purchaser has not attempted to comply with any state takeover statutes in
connection with the Offer. The Purchaser reserves the right to challenge the
validity or applicability of any state law allegedly applicable to the Offer
and nothing in this Offer to Purchase nor any action taken in connection
herewith is intended as a waiver of that right. In the event that any state
takeover statute is found applicable to the Offer, the Purchaser might be
unable to accept for payment or purchase Shares tendered pursuant to the Offer
or be delayed in continuing or consummating the Offer. In such case, the
Purchaser may not be obligated to accept for purchase, or pay for, any Shares
tendered. See Section 14.
 
  Antitrust. Under the HSR Act and the rules that have been promulgated
thereunder by the FTC, certain acquisition transactions may not be consummated
unless certain information has been furnished to the Antitrust Division and the
FTC and certain waiting period requirements have been satisfied. The
acquisition of Shares pursuant to the Offer is subject to such requirements.
See Section 2.
 
  The Parent intends to file on the date hereof with the FTC and the Antitrust
Division a Premerger Notification and Report Form in connection with the
purchase of Shares pursuant to the Offer. Under the
 
                                       35
<PAGE>
 
provisions of the HSR Act applicable to the Offer, the purchase of Shares
pursuant to the Offer may not be consummated until the expiration of a 15-
calendar day waiting period following the filing by the Purchaser. Accordingly,
it is anticipated that the waiting period under the HSR Act applicable to such
purchases of Shares pursuant to the Offer will expire at 11:59 p.m., New York
City time, on Wednesday, November 9, 1994, unless such waiting period is
earlier terminated by the FTC or the Antitrust Division or extended by a
request from the FTC or the Antitrust Division for additional information or
documentary material prior to the expiration of the waiting period. Pursuant to
the HSR Act, the Parent has requested early termination of the waiting period
applicable to the Offer. There can be no assurance, however, that the 15-day
HSR Act waiting period will be terminated early. If, however, either the FTC or
the Antitrust Division were to request additional information or documentary
material from the Parent, the waiting period would expire at 11:59 p.m., New
York City time, on the tenth calendar day after the date of substantial
compliance by the Parent with such request. Thereafter, the waiting period
could be extended only by court order or with the agreement of the Parent. If
the acquisition of Shares is delayed pursuant to a request by the FTC or the
Antitrust Division for additional information or documentary material pursuant
to the HSR Act, the Offer may, but need not, be extended and, in any event, the
purchase of and payment for Shares and Rights will be deferred until 10 days
after the request is substantially complied with, unless the 10-day extended
period expires on or before the date when the initial 15-day period would
otherwise have expired or unless the waiting period is sooner terminated by the
FTC and the Antitrust Division. See Section 2. Only one extension of such
waiting period pursuant to a request for additional information is authorized
by the HSR Act and the rules promulgated thereunder, except by court order or
with the agreement of the Parent. Any such extension of the waiting period will
not give rise to any withdrawal rights not otherwise provided for by applicable
law. See Section 4. Although the Company is required to file certain
information and documentary material with the Antitrust Division and the FTC in
connection with the Offer, neither the Company's failure to make such filings
nor a request from the Antitrust Division or the FTC for additional information
or documentary material made to the Company will extend the waiting period.
 
  The FTC and the Antitrust Division as well as state antitrust enforcement
agencies frequently scrutinize the legality under the antitrust laws of
transactions such as the proposed acquisition of Shares by the Purchaser
pursuant to the Offer. At any time before or after the purchase by the
Purchaser of Shares pursuant to the Offer, any such agency could take such
action under the antitrust laws as it deems necessary or desirable in the
public interest, including seeking to enjoin the purchase of Shares pursuant to
the Offer or seeking the divestiture of Shares purchased by the Purchaser or
the divestiture of substantial assets of the Parent, its subsidiaries or the
Company. Private parties may also bring legal action under federal or state
antitrust laws under certain circumstances.
 
  Based upon an examination of publicly available information relating to the
businesses in which the Parent and its subsidiaries and the Company and its
subsidiaries are engaged, the Parent and the Purchaser believe that the Offer
will not violate the antitrust laws. Nevertheless, there can be no assurance
that a challenge to the Offer on antitrust grounds will not be made or, if such
a challenge is made, of the result.
 
  The Purchaser will not accept for payment Shares tendered pursuant to the
Offer unless and until the waiting period requirements imposed by the HSR Act
with respect to the Offer have been satisfied. See Section 14 for certain
conditions to the Offer, including conditions with respect to litigation.
 
  Foreign Approvals. According to the Company's 1994 Form 10-K, the Company
owns property and conducts business in a number of other foreign countries and
jurisdictions. In connection with the acquisition of the Shares pursuant to the
Offer, the laws of certain of those foreign countries and jurisdictions may
require the filing of information with, or the obtaining of the approval of,
governmental authorities in such countries and jurisdictions. The governments
in such countries and jurisdictions might attempt to impose additional
conditions on the Company's operations conducted in such countries and
jurisdictions as a result of the acquisition of the Shares pursuant to the
Offer. There can be no assurance that the Purchaser will be able to cause the
Company or its subsidiaries to satisfy or comply with such laws or that
compliance or
 
                                       36
<PAGE>
 
noncompliance will not have adverse consequences for the Company or any
subsidiary after purchase of the Shares pursuant to the Offer.
 
  Margin Credit Regulations. Federal Reserve Board Regulations G, T, U and X
(the "Margin Credit Regulations") restrict the extension or maintenance of
credit for the purpose of buying or carrying margin stock, including the
Shares, if the credit is secured directly or indirectly thereby. Such secured
credit may not be extended or maintained in an amount that exceeds the maximum
loan value of the margin stock. Under the Margin Credit Regulations, the Shares
are presently margin stock, and the maximum loan value thereof is generally 50%
of their current market value.
 
  The definition of "indirectly secured" contained in the Margin Credit
Regulations provides that the term does not include an arrangement with a
customer if the lender, in good faith, has not relied upon margin stock as
collateral in extending or maintaining the particular credit.
 
  16. FEES AND EXPENSES. Lehman Brothers Inc. is acting as Dealer Manager in
connection with the Offer and serving as financial advisor to the Parent and
the Purchaser in connection with the proposed acquisition of the Company. If
the Parent acquires control of, or a material interest in, the Company, either
during the term of the Dealer Manager's engagement or within 12 months after
termination thereof, the Parent will pay the Dealer Manager a fee of $2.5
million. The Parent and the Purchaser will also reimburse the Dealer Manager
for reasonable out-of-pocket expenses, including reasonable attorneys' fees,
and have also agreed to indemnify the Dealer Manager against certain
liabilities and expenses in connection with the Offer, including certain
liabilities under the federal securities laws.
 
  The Purchaser has retained D.F. King & Co., Inc. to act as the Information
Agent and The First National Bank of Boston to act as the Depositary in
connection with the Offer. The Information Agent may contact holders of Shares
by mail, telephone, telex, telegraph and personal interview and may request
brokers, dealers and other nominee shareholders to forward the Offer materials
to beneficial owners. The Information Agent and the Depositary will receive
reasonable and customary compensation for services relating to the Offer and
will be reimbursed for certain out-of-pocket expenses. The Purchaser and the
Parent have also agreed to indemnify the Information Agent and the Depositary
against certain liabilities and expenses in connection with the Offer,
including certain liabilities under the federal securities law.
 
  The Purchaser will not pay any fees or commissions to any broker or dealer or
any other person for soliciting tenders of Shares pursuant to the Offer (other
than to the Dealer Manager and the Information Agent). Brokers, dealers,
commercial banks and trust companies will, upon request, be reimbursed by the
Purchaser for customary mailing and handling expenses incurred by them in
forwarding offering materials to their customers.
 
  17. MISCELLANEOUS. The Offer is being made solely by this Offer to Purchase
and the related Letter of Transmittal and is being made to all holders of
Shares. The Purchaser is not aware of any state where the making of the Offer
is prohibited by administrative or judicial action pursuant to any valid state
statute. If the Purchaser becomes aware of any valid state statute prohibiting
the making of the Offer or the acceptance of Shares pursuant thereto, the
Purchaser will make a good faith effort to comply with any such state statute
or seek to have such statute declared inapplicable to the Offer. If, after such
good faith effort, the Purchaser cannot comply with such state statute, the
Offer will not be made to nor will tenders be accepted from or on behalf of the
holders of Shares in such state. In any jurisdiction where the securities, blue
sky or other laws require the Offer to be made by a licensed broker or dealer,
the Offer shall be deemed to be made on behalf of the Purchaser by the Dealer
Manager or one or more registered brokers or dealers that are licensed under
the laws of such jurisdiction.
 
  The Purchaser and the Parent have filed with the Commission a Schedule 14D-1
(including exhibits) pursuant to Rule 14d-3 under the Exchange Act, furnishing
certain additional information with respect to
 
                                       37
<PAGE>
 
the Offer, and may file amendments thereto. Such statement and any amendments
thereto, including exhibits, may be inspected and copies may be obtained from
the offices of the Commission (except that they will not be available at the
regional offices of the Commission) in the manner set forth in Section 7 of
this Offer to Purchase.
 
  NO PERSON HAS BEEN AUTHORIZED TO GIVE ANY INFORMATION OR TO MAKE ANY
REPRESENTATION ON BEHALF OF THE PURCHASER OR THE PARENT NOT CONTAINED HEREIN OR
IN THE LETTER OF TRANSMITTAL AND, IF GIVEN OR MADE, SUCH INFORMATION OR
REPRESENTATION MUST NOT BE RELIED UPON AS HAVING BEEN AUTHORIZED.
 
                                          PB ACQUISITION CORP.
 
October 25, 1994
 
                                       38
<PAGE>
 
                                                                      SCHEDULE I
 
        DIRECTORS AND EXECUTIVE OFFICERS OF THE PURCHASER AND THE PARENT
 
  1. Directors and Executive Officers of the Purchaser. The name, business
address, position with the Purchaser, present principal occupation or
employment and five-year employment history of each director and executive
officer of the Purchaser and certain other information are set forth below.
Unless otherwise indicated, each occupation set forth refers to the Purchaser,
each individual is a United States citizen and each individual's business
address is 81 Wyman Street, Waltham, Massachusetts 02254.
 
<TABLE>
<CAPTION>
                                                 POSITION WITH THE PURCHASER,
        NAME, BUSINESS ADDRESS                      PRINCIPAL OCCUPATION OR
           AND CITIZENSHIP                     EMPLOYMENT AND EMPLOYMENT HISTORY
        ----------------------                 ---------------------------------
 <C>                                  <S>
 John W. Wood, Jr.                    Director and President; Director, President and
  Thermedics Inc.                     Chief Executive Officer of Thermedics Inc. since
  470 Wildwood Street                 1984; and Vice President of the Parent since 1994.
  Woburn, MA 01888-1799

 John T. Keiser                       Director and Vice President; Senior Vice President
                                      of Thermedics Inc. since 1994; Vice President of
                                      Thermo Instrument Systems Inc. from 1986 to 1994
                                      and President of Eberline Instruments Corp. from
                                      1985 to 1994.

 Arvin H. Smith                       Director; Executive Vice President of the Parent
                                      since 1991 and Senior Vice President of the Parent
                                      since 1986.
</TABLE>
 
  2. Directors and Executive Officers of the Parent. The name, business
address, position with the Parent, present principal occupation or employment
and five-year employment history of each director and executive officer of the
Parent and certain other information are set forth below. Unless otherwise
indicated, each occupation set forth refers to the Parent, each individual is a
United States citizen and each individual's business address is 81 Wyman
Street, Waltham, Massachusetts 02254.
 
<TABLE>
<CAPTION>
                                                   POSITION WITH THE PARENT,
        NAME, BUSINESS ADDRESS                      PRINCIPAL OCCUPATION OR
           AND CITIZENSHIP                     EMPLOYMENT AND EMPLOYMENT HISTORY
        ----------------------                 ---------------------------------
 <C>                                  <S>
 John M. Albertine                    Director since 1986; Chairman of the Board and
  Albertine Enterprises, Inc.         Chief Executive Officer of Albertine Enterprises,
  11901 Bowman Drive                  Inc., an economic and public policy consulting
  Fredericksburg, VA 22408            firm he formed in 1990; served as Vice Chairman of
                                      Farley Industries, Inc., principally a textile and
                                      apparel manufacturing company, from 1986 until his
                                      resignation from that position in 1990.

 Peter O. Crisp                       Director since 1974; General Partner, Venrock
  Venrock, Inc.,                      Associates, a venture capital firm, for more than
  Room 5600 30 Rockefeller Plaza      five years.
  New York, NY 10112

 Elias P. Gyftopoulos                 Director since 1976; Ford Professor of Mechanical
  Massachusetts Institute of          and Nuclear Engineering, Massachusetts Institute
  Technology                          of Technology for more than five years.
  Room 24-109
  77 Massachusetts Avenue
  Cambridge, MA 02139
</TABLE>
 
                                      I-1
<PAGE>
 
<TABLE>
<CAPTION>
                                                   POSITION WITH THE PARENT,
        NAME, BUSINESS ADDRESS                      PRINCIPAL OCCUPATION OR
           AND CITIZENSHIP                     EMPLOYMENT AND EMPLOYMENT HISTORY
        ----------------------        --------------------------------------------------
 <C>                                  <S>
 George N. Hatsopoulos                Director, Chairman of the Board, President and
                                      Chief Executive Officer since 1956; brother of
                                      John N. Hatsopoulos.

 Frank Jungers                        Director since 1978; Consultant on business and
  65604 Tweed Road                    energy matters since 1977; Vice Chairman of the
  Bend, OR 97701                      Board of Directors of Riedel Environmental
                                      Technologies, Inc., an environmental services and
                                      remediation firm, from 1989 to 1991 and from
                                      January 1989 to July 1989, President.

 Robert A. McCabe                     Director since 1962; President of Pilot Capital
  Pilot Capital Corporation           Corporation (private investments, acquisition
  444 Madison Avenue                  services) since 1987.
  Suite 2103
  New York, NY 10022

 Frank E. Morris                      Director since 1989; President of the Federal
  105 Walpole Street                  Reserve Bank of Boston from 1968 until retirement
  Dover, MA 02030                     in 1988.

 Donald E. Noble                      Director since 1983; For more than 20 years, from
  Rubbermaid Incorporated             1959 to 1980, served as Chief Executive Officer of
  1147 Akron Road                     Rubbermaid Incorporated, a manufacturer of rubber
  Wooster, OH 44691                   and plastic consumer industrial products.

 Hutham S. Olayan                     Director since 1987; President and a director of
  Competrol Real Estate Ltd.,         Competrol Real Estate Limited, a member of the
  Suite 1100                          Olayan Group engaged in private real estate
  505 Park Avenue                     investments, since 1986; served as President and a
  New York, NY 10022                  director of Cresent Diversified Limited, another
  (Citizen of Saudi Arabia)           member of the Olayan Group engaged in private
                                      investments, from 1985 until 1994.

 Roger D. Wellington                  Director since 1986; has served as President and
  25 Hillside Road                    Chief Executive Officer of Wellington Consultants,
  Cumberland, RI 02864                Inc. and of Wellington Associates, international
                                      business consulting firms he founded in 1994 and
                                      1989, respectively; served as Chairman of the
                                      Board of Augat Inc., a manufacturer of
                                      electromechanical components, for over five years
                                      until becoming a consultant in 1989.

 John N. Hatsopoulos                  Chief Financial Officer and Executive Vice
                                      President*; brother of George N. Hatsopoulos.

 Robert C. Howard                     Executive Vice President.*

 Peter G. Pantazelos                  Executive Vice President.*

 Arvin H. Smith                       Executive Vice President since 1991 and Senior
                                      Vice President since 1986.

 William A. Rainville                 Senior Vice President since 1993 and Vice
                                      President since 1986.

 Paul F. Kelleher                     Vice President, Finance.*
</TABLE>
- --------
* Has held present position for more than five years.
 
                                      I-2
<PAGE>
 
  Facsimile copies of the Letter of Transmittal, properly completed and duly
executed, will be accepted. The Letter of Transmittal, certificates for Shares
and/or Rights and any other required documents should be sent or delivered by
each shareholder of the Company or his broker, dealer, commercial bank, trust
company or other nominee to the Depositary as follows:
 
                        THE DEPOSITARY FOR THE OFFER IS:
 
                       THE FIRST NATIONAL BANK OF BOSTON
 
         By Mail:           By Overnight Courier:             By Hand:
 
 
 
 The First National Bank   The First National Bank        BancBoston Trust
        of Boston                 of Boston             Company of New York
   Shareholder Services      Shareholder Services           55 Broadway
         Division                  Division                 Third Floor
    Mail Stop 45-01-19        Mail Stop 45-01-19            New York, NY
      P.O. Box 1889           150 Royall Street
     Boston, MA 02105          Canton, MA 02021
 
                                 By Facsimile
                                Transmission:
 
                                (617) 575-2232
                                (617) 575-2233
 
                              For confirmation:
 
                                (617) 575-2700
 
  Any questions and requests for assistance may be directed to the Information
Agent or the Dealer Manager at their respective telephone numbers and addresses
listed below. Additional copies of this Offer to Purchase, the Letter of
Transmittal and all other tender offer materials may be obtained from the
Information Agent and will be furnished promptly at Purchaser's expense.
Shareholders may also contact their broker, dealer, commercial bank or trust
company for assistance concerning the Offer.
 
                    THE INFORMATION AGENT FOR THE OFFER IS:
 
                             D.F. KING & CO., INC.
 
                                77 Water Street
                            New York, New York 10005
                         (212) 269-5550 (Call Collect)
                                       or
                           (800) 758-5378 (Toll Free)
 
                      THE DEALER MANAGER FOR THE OFFER IS:
 
                                LEHMAN BROTHERS
 
                            3 World Financial Center
                            New York, New York 10285
                        (212) 526-4089 or (212) 526-4758
                                 (Call Collect)

<PAGE>
 
                             LETTER OF TRANSMITTAL
                        TO TENDER SHARES OF COMMON STOCK
            (INCLUDING THE ASSOCIATED COMMON STOCK PURCHASE RIGHTS)
                                       OF
                          PURITAN-BENNETT CORPORATION
 
                       PURSUANT TO THE OFFER TO PURCHASE
                             DATED OCTOBER 25, 1994
 
                                       BY
 
                              PB ACQUISITION CORP.
                          A WHOLLY OWNED SUBSIDIARY OF
                          THERMO ELECTRON CORPORATION
 
   THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK
   CITY TIME, ON TUESDAY, NOVEMBER 22, 1994, UNLESS THE OFFER IS EXTENDED.
 
                        The Depositary for the Offer is:
                       THE FIRST NATIONAL BANK OF BOSTON
 
         By Mail:           By Overnight Courier:            By Hand:
 
 
 
 The First National Bank   The First National Bank       BancBoston Trust
        of Boston                 of Boston             Company of New York
   Shareholder Services      Shareholder Services           55 Broadway
         Division                  Division                 Third Floor
    Mail Stop 45-01-19        Mail Stop 45-01-19           New York, NY
      P.O. Box 1889           150 Royall Street
     Boston, MA 02105          Canton, MA 02021
 
                           By Facsimile Transmission:
 
                                 (617) 575-2232
                                 (617) 575-2233
 
                               For confirmation:
 
                                 (617) 575-2700
 
  DELIVERY OF THIS LETTER OF TRANSMITTAL TO AN ADDRESS OTHER THAN AS SET FORTH
ABOVE, OR TRANSMISSIONS OF INSTRUCTIONS VIA A FACSIMILE NUMBER OTHER THAN AS
SET FORTH ABOVE, WILL NOT CONSTITUTE A VALID DELIVERY.
 
  THE INSTRUCTIONS ACCOMPANYING THIS LETTER OF TRANSMITTAL SHOULD BE READ
CAREFULLY BEFORE THIS LETTER OF TRANSMITTAL IS COMPLETED.
 
  This Letter of Transmittal is to be completed by shareholders, either if
certificates representing Shares or Rights (as such terms are defined below)
are to be forwarded herewith or, unless an Agent's Message (as defined in the
Offer to Purchase) is utilized, if tenders of Shares or Rights are to be made
by book-entry transfer into the account of The First National Bank of Boston,
as Depositary (the "Depositary"), at The Depository Trust Company ("DTC"), the
Midwest Securities Trust Company ("MSTC") or the Philadelphia Depository Trust
Company ("PDTC") (each a "Book-Entry Transfer Facility" and, collectively, the
"Book-Entry Transfer Facilities") pursuant to the procedures set forth in
Section 3 of the Offer to Purchase (as defined below). Shareholders who tender
Shares or Rights by book-entry transfer are referred to herein as "Book-Entry
Shareholders".
 
  Unless, on or before the Expiration Date, the Rights have been redeemed by
the Board of Directors of Puritan-Bennett Corporation, a Delaware corporation
(the "Company"), holders of Shares will be required to tender one Right for
each Share tendered in order to effect a valid tender of such Share. If
separate certificates for the Rights are not issued, a tender of Shares will
also constitute a tender of the associated Rights. If the Distribution Date (as
defined in the Offer to Purchase) has occurred and certificates representing
Rights (the "Rights Certificates") have been distributed to holders of Shares
prior to the date of tender pursuant to the Offer, in order for Rights (and the
corresponding Shares) to be validly tendered, Rights Certificates representing
a number of Rights equal to the number of Shares being tendered must be
delivered to The First National Bank of Boston (the "Depositary") or, if
available, a confirmation of book-entry transfer (a "Book-Entry Confirmation")
must be received by the Depositary with respect thereto. If the Distribution
Date has occurred and Rights Certificates have not been distributed prior to
the time Shares are tendered pursuant to the Offer, Rights may be tendered
prior to a shareholder receiving Rights Certificates by use of the guaranteed
delivery procedures described in Section 3 of the Offer to Purchase. In any
case, a tender of Shares without Rights Certificates constitutes an agreement
by the tendering shareholder to deliver Rights Certificates representing a
number of Rights equal to the number of Shares tendered pursuant to the Offer
to the Depositary within five business days after the date such Rights
Certificates are distributed. See Section 3 of the Offer to Purchase. Unless,
on or before the Expiration Date, the Rights have been redeemed by the
Company's Board of Directors, the Purchaser reserves the right to require that
the Depositary receive such Rights Certificates, or Book-Entry Confirmation, if
available, with respect to such Rights, prior to accepting the related Shares
for payment. In that event, payment for Shares tendered and accepted for
payment pursuant to the Offer will be made only after timely receipt by the
Depositary of, among other things, Rights Certificates, or Book-Entry
Confirmation, if available, with respect to such Rights, if Rights Certificates
have been distributed to holders of Shares. See Section 2 of the Offer to
Purchase. Holders of Shares and Rights whose certificates representing such
Shares (the "Share Certificates") and, if applicable, whose Rights
Certificates, are not immediately available (including because Rights
Certificates have not yet been distributed by the Company) or who cannot
deliver their Share Certificates or, if applicable, Rights Certificates, and
all other required documents to reach the Depositary on or prior to the
Expiration Date (as defined in Section 1 of the Offer to Purchase), or who
cannot complete the procedure for delivery by book-entry transfer on a timely
basis, may tender their Shares and Rights according to the guaranteed delivery
procedures set forth in Section 3 of the Offer to Purchase. See Instruction 2.
DELIVERY OF DOCUMENTS TO A BOOK-ENTRY TRANSFER FACILITY DOES NOT CONSTITUTE
DELIVERY TO THE DEPOSITARY.
<PAGE>
 

- --------------------------------------------------------------------------------
                         DESCRIPTION OF SHARES TENDERED
- --------------------------------------------------------------------------------
  NAME(S) AND ADDRESS(ES) OF REGISTERED HOLDER(S) (PLEASE FILL IN, IF BLANK,
     EXACTLY AS NAME(S) APPEAR(S) ON SHARE CERTIFICATE(S))
- --------------------------------------------------------------------------------




                  SHARE CERTIFICATE(S) AND SHARE(S) TENDERED 
                 (ATTACH ADDITIONAL SIGNED LIST, IF NECESSARY)
- --------------------------------------------------------------------------------
                       TOTAL NUMBER     
                         OF SHARES    
                        REPRESENTED        NUMBER
    SHARE CERTIFICATE    BY SHARE        OF SHARES
        NUMBER(S)*    CERTIFICATE(S)*    TENDERED**
     ---------------  ---------------  ---------------
     ---------------  ---------------  ---------------
     ---------------  ---------------  ---------------
     ---------------  ---------------  ---------------
     ---------------  ---------------  ---------------
      TOTAL SHARES ...................               
- --------------------------------------------------------------------------------
   * Need not be completed by Book-Entry Shareholders.
  ** Unless otherwise indicated, all Shares represented by certificates
     delivered to the Depositary will be deemed to have been tendered. See
     Instruction 4.
- --------------------------------------------------------------------------------
                        DESCRIPTION OF RIGHTS TENDERED*
- --------------------------------------------------------------------------------
  NAME(S) AND ADDRESS(ES) OF REGISTERED HOLDERS(S) (PLEASE FILL IN, IF BLANK,
            EXACTLY AS NAME(S) APPEAR(S) ON RIGHTS CERTIFICATE(S))
- --------------------------------------------------------------------------------




                  RIGHTS CERTIFICATE(S) AND RIGHTS TENDERED  
                (ATTACH ADDITIONAL SIGNED LIST, IF NECESSARY) 
- --------------------------------------------------------------------------------
                        TOTAL NUMBER     
                         OF RIGHTS    
                        REPRESENTED        NUMBER
    RIGHTS CERTIFICATE   BY RIGHTS        OF RIGHTS
        NUMBER(S)*    CERTIFICATE(S)*     TENDERED**
     ---------------  ---------------  ---------------
     ---------------  ---------------  ---------------
     ---------------  ---------------  ---------------
     ---------------  ---------------  ---------------
     ---------------  ---------------  ---------------
      TOTAL RIGHTS ...................                
- --------------------------------------------------------------------------------
   * Need not be completed if the Distribution Date (as defined in the Offer
     to Purchase) has not occurred.
  ** Need not be completed by Book-Entry Shareholders.
 *** Unless otherwise indicated, all Rights represented by certificates
     delivered to the Depositary will be deemed to have been tendered. See
     Instruction 4.
<PAGE>
 
[_]  CHECK HERE IF SHARES ARE BEING TENDERED BY BOOK-ENTRY TRANSFER MADE TO
     AN ACCOUNT MAINTAINED BY THE DEPOSITARY WITH A BOOK-ENTRY TRANSFER FACILITY
     AND COMPLETE THE FOLLOWING (ONLY PARTICIPANTS IN A BOOK-ENTRY TRANSFER
     FACILITY MAY DELIVER SHARES BY BOOK-ENTRY TRANSFER):

     Name of Tendering Institution: ____________________________________________
 
     Check box of Book-Entry Transfer Facility:
 
     [_]  The Depository Trust Company
     [_]  Midwest Securities Trust Company
     [_]  Philadelphia Depository Trust Company
 
     Account Number: __________   Transaction Code Number: _____________________
 
[_]  CHECK HERE IF SHARES ARE BEING TENDERED PURSUANT TO A NOTICE OF GUARANTEED
     DELIVERY PREVIOUSLY SENT TO THE DEPOSITARY AND COMPLETE THE FOLLOWING.
     PLEASE ENCLOSE A PHOTOCOPY OF SUCH NOTICE OF GUARANTEED DELIVERY:
 
     Name(s) of Registered Holder(s): __________________________________________
 
     Window Ticket Number (if any): ____________________________________________
 
     Date of Execution of Notice of Guaranteed Delivery: _______________________
 
     Name of Institution that Guaranteed Delivery: _____________________________
 
     If delivered by Book-Entry Transfer check box of Book-Entry Transfer
      Facility:
 
     [_]  The Depository Trust Company
     [_]  Midwest Securities Trust Company
     [_]  Philadelphia Depository Trust Company
 
     Account Number: __________   Transaction Code Number: _____________________
 
[_]  CHECK HERE IF RIGHTS ARE BEING TENDERED BY BOOK-ENTRY TRANSFER MADE TO AN
     ACCOUNT MAINTAINED BY THE DEPOSITARY WITH A BOOK-ENTRY TRANSFER FACILITY
     AND COMPLETE THE FOLLOWING (ONLY PARTICIPANTS IN A BOOK-ENTRY TRANSFER
     FACILITY MAY DELIVER SHARES BY BOOK-ENTRY TRANSFER):
 
     Name of Tendering Institution: ____________________________________________
 
     Check box of Book-Entry Transfer Facility:
 
     [_]  The Depository Trust Company
     [_]  Midwest Securities Trust Company
     [_]  Philadelphia Depository Trust Company
 
     Account Number: __________   Transaction Code Number: _____________________
 
[_]  CHECK HERE IF RIGHTS ARE BEING TENDERED PURSUANT TO A NOTICE OF GUARANTEED
     DELIVERY PREVIOUSLY SENT TO THE DEPOSITARY AND COMPLETE THE FOLLOWING.
     PLEASE ENCLOSE A PHOTOCOPY OF SUCH NOTICE OF GUARANTEED DELIVERY:
 
     Name(s) of Registered Holder(s): __________________________________________
 
     Window Ticket Number (if any): ____________________________________________
 
     Date of Execution of Notice of Guaranteed Delivery: _______________________
 
     Name of Institution that Guaranteed Delivery: _____________________________
 
     If delivered by Book-Entry Transfer check box of Book-Entry Transfer
      Facility:
 
     [_]  The Depository Trust Company
     [_]  Midwest Securities Trust Company
     [_]  Philadelphia Depository Trust Company
 
     Account Number: __________   Transaction Code Number: _____________________

<PAGE>
 
                    NOTE: SIGNATURES MUST BE PROVIDED BELOW
              PLEASE READ THE ACCOMPANYING INSTRUCTIONS CAREFULLY
 
Ladies and Gentlemen:
  The undersigned hereby tenders to PB Acquisition Corp., a Delaware
corporation (the "Purchaser") and a wholly owned subsidiary of Thermo Electron
Corporation, a Delaware corporation (the "Parent"), the above-described shares
of Common Stock, $1.00 par value per share (the "Shares"), of Puritan-Bennett
Corporation, a Delaware corporation (the "Company"), and (unless, on or before
the Expiration Date (as defined in the Offer to Purchase) the associated
Common Stock Purchase Rights (the "Rights") have been redeemed by the
Company's Board of Directors), the Rights issued pursuant to the Rights
Agreement, dated as of May 2, 1989 (the "Rights Agreement"), between the
Company and United Missouri Bank of Kansas City, N.A., as Rights Agent (the
"Rights Agent"), at a purchase price of $24.50 per Share (and associated
Right), net to the seller in cash, without interest thereon, upon the terms
and subject to the conditions set forth in the Offer to Purchase dated October
25, 1994 (the "Offer to Purchase") and in this Letter of Transmittal (which
together constitute the "Offer"). Unless the context requires otherwise, all
references to "Shares" shall be deemed to refer also to the Rights, and all
references to "Rights" shall be deemed to include all benefits that may inure
to the shareholders of the Company or to holders of the Rights pursuant to the
Rights Agreement. The undersigned understands that the Purchaser reserves the
right to transfer or assign, in whole or from time to time in part, to one or
more of its affiliates, the right to purchase all or any portion of the Shares
tendered pursuant to the Offer, receipt of which is hereby acknowledged.
  The undersigned understands that unless, on or before the Expiration Date,
the Rights have been redeemed by the Company's Board of Directors, holders of
Shares will be required to tender one Right for each Share tendered in order
to effect a valid tender of such Share. If separate certificates for the
Rights are not issued, a tender of Shares will also constitute a tender of the
associated Rights. If the Distribution Date (as defined in the Offer to
Purchase) has occurred and certificates representing Rights (the "Rights
Certificates") have been distributed to holders of Shares prior to the date of
tender of the Shares and Rights tendered herewith, in order for Rights (and
the corresponding Shares) to be validly tendered, Rights Certificates
representing a number of Rights equal to the number of Shares being tendered
herewith must be delivered to the Depositary or, if available, a Book-Entry
Confirmation must be received by the Depositary with respect thereto. If the
Distribution Date has occurred and Rights Certificates have not been
distributed prior to the time Shares are tendered herewith, Rights may be
tendered prior to a shareholder receiving Rights Certificates by use of the
guaranteed delivery procedures described in Section 3 of the Offer to
Purchase. In any case, a tender of Shares without Rights Certificates
constitutes an agreement by the tendering shareholder to deliver Rights
Certificates representing a number of Rights equal to the number of Shares
tendered pursuant to the Offer to the Depositary within five business days
after the date such Rights Certificates are distributed. The undersigned
understands that unless, on or before the Expiration Date, the Rights have
been redeemed by the Company's Board of Directors, the Purchaser reserves the
right to require that the Depositary receive such Rights Certificates, or
Book-Entry Confirmation, if available, with respect to such Rights, prior to
accepting the related Shares for payment. In that event, payment for Shares
tendered and accepted for payment pursuant to the Offer will be made only
after timely receipt by the Depositary of, among other things, Rights
Certificates, or Book-Entry Confirmation, if available, with respect to such
Rights, if Rights Certificates have been distributed to holders of Shares.
  Subject to, and effective upon, acceptance for payment of the Shares and
Rights tendered herewith in accordance with the terms and subject to the
conditions of the Offer, the undersigned hereby sells, assigns and transfers
to, or upon the order of, the Purchaser all right, title and interest in and
to all of the Shares and Rights that are being tendered hereby and any and all
dividends, except for regular quarterly cash dividends not in excess of $.03
per Share, having customary and usual record and payment dates, distributions
(including additional Shares) or rights declared, paid or issued with respect
to the tendered Shares on or after October 24, 1994 (except that if the Rights
are redeemed by the Company's Board of Directors in accordance with the terms
of the Rights Agreement, tendering shareholders who are holders of record as
of the applicable record date will be entitled to receive and retain the
redemption price of $.01 per Right in accordance with the Rights Agreement)
(collectively, a "Distribution"), and appoints the Depositary the true and
lawful agent and attorney-in-fact of the undersigned with respect to such
Shares and Rights (and any Distribution) with full power of substitution (such
power of attorney being deemed to be an irrevocable power coupled with an
interest) to (a) deliver such Share Certificates (as defined herein) and
Rights Certificates (and any Distribution), or transfer ownership of such
Shares and Rights (and any Distribution) on the account books maintained by a
Book-Entry Transfer Facility, together in any case with appropriate evidences
of transfer and authenticity, to, or upon the order of, the Purchaser, upon
receipt by the Depositary, as the undersigned's agent, of the purchase price,
(b) present such Shares and Rights (and any Distributions) for transfer on the
books of the Company and (c) receive all benefits and otherwise exercise all
rights of beneficial ownership of such Shares and Rights (and any
Distribution), all in accordance with the terms and subject to the conditions
of the Offer.
<PAGE>
 
  The undersigned hereby irrevocably appoints George N. Hatsopoulos, John N.
Hatsopoulos and Seth H. Hoogasian, and each of them, or any other designees of
the Purchaser as attorneys-in-fact and proxies of the undersigned, each with
full power of substitution, to the full extent of the undersigned's rights
with respect to the Shares and Rights tendered by the undersigned and accepted
for payment and paid for by the Purchaser (and with respect to any and all
other Shares or other securities issued or issuable in respect of such Shares
on or after October 25, 1994). This power of attorney and proxy shall be
considered irrevocable and coupled with an interest in the tendered Shares and
Rights. Such appointment will be effective when, and only to the extent that,
the Purchaser accepts such Shares and Rights for payment and deposits the
purchase price therefor with the Depositary. Upon such payment, all prior
powers of attorney and proxies given by the undersigned with respect to such
Shares and Rights (and such other shares and securities) will be revoked
without further action, and no subsequent powers of attorney or proxies may be
given nor any subsequent written consents executed by the undersigned (and, if
given or executed, will not be deemed effective). The designees of the
Purchaser will be empowered to exercise all voting and other rights of the
undersigned as they in their sole discretion may deem proper at any annual or
special meeting of the Company's shareholders or any adjournment or
postponement thereof, by written consent in lieu of any such meeting or
otherwise. The Purchaser reserves the right to require that, in order for
Shares and Rights to be deemed validly tendered, immediately upon the
Purchaser's payment for such Shares, the Purchaser must be able to exercise
full voting rights with respect to such Shares, Rights and other securities,
including voting at any meeting of shareholders.
  The undersigned hereby represents and warrants that (a) the undersigned has
full power and authority to tender, sell, assign and transfer the Shares and
Rights tendered hereby (and any Distribution) and (b) when the Shares and
Rights are accepted for payment by the Purchaser, the Purchaser will acquire
good, marketable and unencumbered title to the Shares and Rights (and any
Distribution), free and clear of all liens, restrictions, charges and
encumbrances, and the same will not be subject to any adverse claim. The
undersigned, upon request, will execute and deliver any additional documents
deemed by the Depositary or the Purchaser to be necessary or desirable to
complete the sale, assignment and transfer of the Shares and Rights tendered
hereby (and any Distribution). In addition, the undersigned shall promptly
remit and transfer to the Depositary for the account of the Purchaser any
Distribution, in respect of the Shares and Rights tendered hereby, accompanied
by appropriate documentation of transfer, and, pending such remittance or
appropriate assurance thereof, the Purchaser will be, subject to applicable
law, entitled to all rights and privileges as owner of any such Distribution
and may withhold the entire purchase price of Shares tendered hereby or deduct
from the purchase price the amount or value thereof, as determined by the
Purchaser in its sole discretion.
  All authority herein conferred or agreed to be conferred shall not be
affected by and shall survive the death or incapacity of the undersigned and
any obligation of the undersigned hereunder shall be binding upon the heirs,
personal representatives, successors and assigns of the undersigned.
  Tenders of Shares and Rights made pursuant to the Offer are irrevocable,
except that Shares and Rights tendered pursuant to the Offer may be withdrawn
at any time prior to the Expiration Date (as defined in the Offer to Purchase)
and, unless theretofore accepted for payment by the Purchaser pursuant to the
Offer, may also be withdrawn at any time after December 23, 1994 (or such
later date as may apply in case the Offer is extended). See Section 4 of the
Offer to Purchase.
  The undersigned understands that tenders of Shares and Rights pursuant to
any of the procedures described in Section 3 of the Offer to Purchase and in
the instructions hereto will constitute a binding agreement between the
undersigned and the Purchaser upon the terms and subject to the conditions set
forth in the Offer, including the undersigned's representation that the
undersigned owns the Shares and Rights being tendered.
  Unless otherwise indicated herein under "Special Payment Instructions",
please issue the check for the purchase price and/or issue or return any
certificate(s) for Shares and Rights not tendered or not accepted for payment
in the name(s) of the registered holder(s) appearing under "Description of
Shares Tendered" and "Description of Rights Tendered", respectively.
Similarly, unless otherwise indicated herein under "Special Delivery
Instructions", please mail the check for the purchase price and/or return any
certificate(s) for Shares and Rights not tendered or not accepted for payment
(and accompanying documents, as appropriate) to the address(es) of the
registered holder(s) appearing under "Description of Shares Tendered" and
"Description of Rights Tendered", respectively. In the event that both the
Special Delivery Instructions and the Special Payment Instructions are
completed, please issue the check for the purchase price and/or return any
certificate(s) for Shares and Rights not tendered or accepted for payment in
the name of, and deliver such check and/or return such certificate(s) to, the
person(s) so indicated. Unless otherwise indicated herein under "Special
Payment Instructions", please credit any Shares and Rights tendered herewith
by book-entry transfer that are not accepted for payment by crediting the
account at the Book-Entry Transfer Facility designated above. The undersigned
recognizes that the Purchaser has no obligation, pursuant to the Special
Payment Instructions, to transfer any Shares or Rights from the name(s) of the
registered holder(s) thereof if the Purchaser does not accept for payment any
of the Shares or Rights tendered hereby.
<PAGE>
 
 ------------------------------------      ---------------------------------- 
 SPECIAL PAYMENT INSTRUCTIONS (SEE           SPECIAL DELIVERY INSTRUCTIONS
    INSTRUCTIONS 1, 5, 6 AND 7)             (SEE INSTRUCTIONS 1, 5, 6 AND 7)

  To be completed ONLY if certifi-          To be completed ONLY if certifi-
 cate(s) for Shares and Rights not         cate(s) for Shares and Rights not
 tendered or not accepted for pay-         tendered or not accepted for pay-
 ment and/or the check for the             ment and/or the check for the
 purchase price of Shares and              purchase price of Shares and
 Rights accepted for payment are           Rights accepted for payment are
 to be issued in the name of some-         to be sent to someone other than
 one other than the undersigned or         the undersigned or to the under-
 if Shares or Rights tendered by           signed at an address other than
 book-entry transfer which are not         that shown above.
 accepted for payment are to be          
 returned by credit to an account          Mail  [_] check  [_] certificates  
 maintained at a Book-Entry Trans-         to:                                
 fer Facility other than the ac-           Name______________________________ 
 count indicated above.                              (PLEASE PRINT)           
                                                                                
 Issue  [_] check  [_] certificates        Address __________________________   
 to:                                                                         
                                           __________________________________
                                                   (INCLUDE ZIP CODE)        
 Name _____________________________                                           
            (PLEASE PRINT)                 __________________________________ 
                                             (TAX IDENTIFICATION OR SOCIAL     
 Address __________________________               SECURITY NO.)               
                                                                           
 __________________________________                                            
          (INCLUDE ZIP CODE)                                                   
                                                                               
 __________________________________      
    (TAX IDENTIFICATION OR SOCIAL        
            SECURITY NO.)                
   (SEE SUBSTITUTE FORM W-9 ON THE       
            REVERSE SIDE)                
  Credit Shares and Rights tendered      
  by book-entry transfer that are        
  not accepted for payment to            
  (Check one):                           
  [_] DTC  [_] MSTC  [_] PDTC            
 __________________________________      
   (DTC, MSTC OR PDTC ACCOUNT NO.)       

 ------------------------------------      ---------------------------------- 


              



















<PAGE>
 
      -------------------------------------------------------------------
                                   IMPORTANT
             SIGN HERE AND COMPLETE SUBSTITUTE FORM W-9 ON REVERSE
SIGN                                                                        SIGN
HERE    X ............................................................      HERE

- ---)    X ............................................................      (---
                          (SIGNATURE(S) OF HOLDER(S))

        Dated: ............................................., 19......
        (Must be signed by the registered holder(s) exactly as name(s) 
        appear(s) on Share Certificate(s) or Rights Certificates(s) or 
        on a security position listing or by person(s) authorized to 
        become registered holder(s) by certificates and documents
        transmitted herewith. If signature is by trustees, executors, 
        administrators, guardians, attorneys-in-fact, officers of 
        corporations or others acting in a fiduciary or representative 
        capacity, please provide the following information and see
        Instruction 5.)
 
        Name(s):  ....................................................

                  ....................................................
                                (PLEASE PRINT)
 
        Capacity (full title):  ......................................
 
        Address:  ....................................................
 
                  ....................................................
                              (INCLUDE ZIP CODE)
 
        Area Code and Telephone Number: ..............................
 
        Tax Identification or
        Social Security No.: .........................................
 
                    COMPLETE SUBSTITUTE FORM W-9 ON REVERSE
                          GUARANTEE OF SIGNATURE(S) 
                          (SEE INSTRUCTIONS 1 AND 5)
 
        Authorized Signature: ........................................
 
        Name:  .......................................................
 
        Name of Firm:  ...............................................
                                (PLEASE PRINT)
 
        Address:  ....................................................
 
                  ....................................................
                              (INCLUDE ZIP CODE)
 
        Area Code and Telephone Number: ..............................
 
        Dated:  ............................................, 19......
      -------------------------------------------------------------------
<PAGE>
 
                                  INSTRUCTIONS
 
             FORMING PART OF THE TERMS AND CONDITIONS OF THE OFFER
 
  1. GUARANTEE OF SIGNATURES. No signature guarantee is required on this Letter
of Transmittal (a) if this Letter of Transmittal is signed by the registered
holder(s) of Shares and Rights (which term, for purposes of this document,
shall include any participant in a Book-Entry Transfer Facility whose name
appears on a security position listing as the owner of Share(s) and/or Rights)
tendered herewith, unless such holder(s) has completed either the box entitled
"Special Payment Instructions" or the box entitled "Special Delivery
Instructions" above, or (b) if such Share(s) and/or Right(s) are tendered for
the account of a firm which is a bank, broker, dealer, credit union, savings
association or other entity which is a member in good standing of the
Securities Transfer Agents Medallion Program (each of the foregoing being
referred to as an "Eligible Institution"). In all other cases, all signatures
on this Letter of Transmittal must be guaranteed by an Eligible Institution.
See Instruction 5 of this Letter of Transmittal.
 
  2. REQUIREMENTS OF TENDER. This Letter of Transmittal is to be completed by
shareholders either if certificates for Shares or Rights are to be forwarded
herewith or, unless an Agent's Message is utilized, if tenders of Shares or
Rights are to be made by book-entry transfer pursuant to the procedures set
forth in Section 3 of the Offer to Purchase. In order for Shares to be validly
tendered pursuant to the Offer, this Letter of Transmittal (or a facsimile
hereof), properly completed and duly executed, together with any required
signature guarantees, or an Agent's Message in connection with a book-entry
delivery of Shares and Rights, and any other documents required by this Letter
of Transmittal, must be received by the Depositary at one of its addresses set
forth on the back cover of the Offer to Purchase on or prior to the Expiration
Date and either (i) Share Certificates and Rights Certificates, if applicable,
representing tendered Shares and Rights must be received by the Depositary at
such address or such Shares and Rights must be tendered by book-entry transfer
and a timely confirmation of such book-entry transfer (a "Book-Entry
Confirmation") must be received by the Depositary, in each case on or prior to
the Expiration Date, or (ii) the guaranteed delivery procedures described in
the following sentence must be complied with. Shareholders whose Share
Certificates or Rights Certificates are not immediately available (including
because Rights Certificates have not yet been distributed by the Company) or
who cannot deliver their Share Certificates or Rights Certificates and all
other required documents to reach the Depositary on or prior to the Expiration
Date or who cannot complete the procedure for delivery by book-entry transfer
on a timely basis may tender their Shares and Rights by properly completing and
duly executing a Notice of Guaranteed Delivery pursuant to the guaranteed
delivery procedures set forth in Section 3 of the Offer to Purchase. Pursuant
to such procedure: (i) such tender must be made by or through an Eligible
Institution; (ii) a properly completed and duly executed Notice of Guaranteed
Delivery, substantially in the form made available by the Purchaser, must be
received by the Depositary on or prior to the Expiration Date; (iii) the Share
Certificates (or a Book-Entry Confirmation) representing all tendered Shares,
in proper form for transfer, in each case together with this Letter of
Transmittal (or a facsimile hereof), properly completed and duly executed, with
any required signature guarantees (or, in the case of a book-entry delivery, an
Agent's Message) and any other documents required by this Letter of
Transmittal, must be received by the Depositary within five Nasdaq National
Market ("NNM") trading days after the date of execution of such Notice of
Guaranteed Delivery; and (iv) unless, on or before the Expiration Date, the
Rights have been redeemed by the Company's Board of Directors, the Rights
Certificates, if issued (or a Book-Entry Confirmation, if available)
representing the appropriate number of Rights in proper form for transfer, in
each case together with a properly completed and duly executed Letter of
Transmittal (or a facsimile hereof), with any required signature guarantees
(or, in the case of a book-entry delivery, an Agent's Message) and any other
documents required by this Letter of Transmittal, must be received by the
Depositary within five NNM trading days after the date of execution of such
Notice of Guaranteed Delivery or, if later, five NNM trading days after the
date the Rights Certificates are distributed to shareholders of the Company,
all as provided in Section 3 of the Offer to Purchase. If Share Certificates
and Rights Certificates are forwarded separately to the Depositary, a properly
completed and duly executed Letter of Transmittal (or facsimile hereof) must
accompany each such delivery.
 
  THE METHOD OF DELIVERY OF SHARE CERTIFICATES OR OF RIGHTS CERTIFICATES, IF
APPLICABLE, AND ALL OTHER REQUIRED DOCUMENTS, INCLUDING DELIVERY THROUGH ANY
BOOK-ENTRY TRANSFER FACILITY, IS AT THE OPTION AND SOLE RISK OF THE TENDERING
SHAREHOLDER AND THE DELIVERY WILL BE DEEMED MADE ONLY WHEN ACTUALLY RECEIVED BY
THE DEPOSITARY. IF DELIVERY IS BY MAIL, REGISTERED MAIL WITH RETURN RECEIPT
REQUESTED, PROPERLY INSURED, IS RECOMMENDED. IN ALL CASES, SUFFICIENT TIME
SHOULD BE ALLOWED TO ENSURE TIMELY DELIVERY.
<PAGE>
 
  No alternative, conditional or contingent tenders will be accepted and no
fractional Shares and Rights will be purchased. All tendering shareholders, by
execution of this Letter of Transmittal (or a facsimile hereof), waive any
right to receive any notice of the acceptance of their Shares and Rights for
payment.
 
  3. INADEQUATE SPACE. If the space provided herein is inadequate, the
certificate numbers and/or the number of Shares and Rights and any other
required information should be listed on a separate signed schedule attached
hereto.
 
  4. PARTIAL TENDERS. (Not Applicable to Book-Entry Stockholders) If fewer than
all the Shares evidenced by any Share Certificate submitted are to be tendered,
fill in the number of Shares which are to be tendered in the box entitled
"Number of Shares Tendered". If fewer than all the Rights evidenced by any
Rights Certificates submitted are to be tendered, fill in the number of Rights
which are to be tendered in the box entitled "Number of Rights Tendered". In
such cases, new Share Certificates or Rights Certificates, as the case may be,
for the Shares or Rights that were evidenced by your old Share Certificates or
Rights Certificates, but were not tendered by you, will be sent to you, unless
otherwise provided in the appropriate box on this Letter of Transmittal, as
soon as practicable after the Expiration Date. All Shares represented by Share
Certificates and all Rights represented by Rights Certificates delivered to the
Depositary will be deemed to have been tendered unless otherwise indicated.
 
  5. SIGNATURES ON LETTER OF TRANSMITTAL, STOCK POWERS AND ENDORSEMENTS. If
this Letter of Transmittal is signed by the registered holder(s) of the Shares
and Rights tendered hereby, the signature(s) must correspond with the name(s)
as written on the face of the certificate(s) without alteration, enlargement or
any change whatsoever.
 
  If any of the Shares and Rights tendered hereby are owned of record by two or
more joint owners, all such owners must sign this Letter of Transmittal.
 
  If any of the tendered Shares and Rights are registered in different names on
several certificates, it will be necessary to complete, sign and submit as many
separate Letters of Transmittal as there are different registrations of
certificates.
 
  If this Letter of Transmittal or any certificates or stock powers are signed
by trustees, executors, administrators, guardians, attorneys-in-fact, officers
of corporations or others acting in a fiduciary or representative capacity,
such persons should so indicate when signing, and proper evidence satisfactory
to the Purchaser of their authority so to act must be submitted.
 
  If this Letter of Transmittal is signed by the registered holder(s) of the
Shares and Rights listed and transmitted hereby, no endorsements of
certificates or separate stock powers are required unless payment is to be made
to or certificates for Shares or Rights not tendered or not purchased are to be
issued in the name of a person other than the registered holder(s). Signatures
on such certificates or stock powers must be guaranteed by an Eligible
Institution.
 
  If this Letter of Transmittal is signed by a person other than the registered
holder(s) of the certificate(s) listed, the certificate(s) must be endorsed or
accompanied by appropriate stock powers, in either case signed exactly as the
name(s) of the registered holder(s) appear on the certificate(s). Signatures on
such certificates or stock powers must be guaranteed by an Eligible
Institution.
 
  Unless, on or before the Expiration Date, the Rights have been redeemed by
the Company's Board of Directors, if Rights Certificates have been distributed
to holders of Shares, such holders are required to tender Rights Certificate(s)
representing a number of Rights equal to the number of Shares tendered in order
to effect a valid tender of such Shares. It is necessary that shareholders
follow all signature requirements of this Instruction 5 with respect to the
Rights in order to tender such Rights.
 
  6. STOCK TRANSFER TAXES. The Purchaser will pay any stock transfer taxes with
respect to the transfer and sale of Shares and Rights to it or its order
pursuant to the Offer. If, however, payment of the purchase price is to be made
to, or if certificates for Shares and Rights not tendered or accepted for
payment are to be registered in the name of, any person other than the
registered holder(s), or if tendered certificates are registered in the name of
any person other than the person(s) signing this Letter of Transmittal, the
amount of any stock transfer taxes (whether imposed on the registered holder(s)
or such person) payable on account of the transfer to such person will be
deducted from the purchase price unless satisfactory evidence of the payment of
such taxes or an exemption therefrom is submitted.
 
  EXCEPT AS PROVIDED IN THIS INSTRUCTION 6, IT WILL NOT BE NECESSARY FOR
TRANSFER TAX STAMPS TO BE AFFIXED TO THE CERTIFICATE(S) LISTED IN THIS LETTER
OF TRANSMITTAL.
<PAGE>
 
  7. SPECIAL PAYMENT AND DELIVERY INSTRUCTIONS. If a check is to be issued in
the name of, and/or certificates for Shares and Rights not tendered or not
accepted for payment are to be issued or returned to, a person other than the
signer of this Letter of Transmittal or if a check and/or such certificates are
to be returned to a person other than the signer of this Letter of Transmittal
or to an address of the signer other than that shown in this Letter of
Transmittal, the appropriate boxes on this Letter of Transmittal must be
completed. Book-Entry Shareholders may request that Shares and/or Rights not
accepted for payment be credited to such account maintained at a Book-Entry
Transfer Facility as such Book-Entry Shareholder may designate under "Special
Payment Instructions". If no such instructions are given, such Shares or Rights
not accepted for payment will be returned by crediting the account at the Book-
Entry Transfer Facility designated above.
 
  8. WAIVER OF CONDITIONS. The conditions of the Offer may be waived by the
Purchaser, in whole or in part, at any time and from time to time in its sole
discretion.
 
  9. 31% BACKUP WITHHOLDING; SUBSTITUTE FORM W-9. Under U.S. federal income tax
law, a shareholder whose tendered Shares or Rights are accepted for payment is
required to provide the Depositary with such shareholder's correct taxpayer
identification number ("TIN") on Substitute Form W-9 below. If the Depositary
is not provided with the correct TIN (e.g., social security number or employer
identification number), the Internal Revenue Service may subject the
shareholder or other payee to penalties. In addition, payments that are made to
such shareholder or other payee with respect to Shares or Rights purchased
pursuant to the Offer may be subject to 31% backup withholding.
 
  Certain shareholders are not subject to these backup withholding and
reporting requirements. In order for a foreign individual to qualify as an
exempt recipient, the shareholder must submit a Form W-8, signed under
penalties of perjury, attesting to that individual's exempt status. A Form W-8
can be obtained from the Depositary. See the enclosed "Guidelines for
Certification of Taxpayer Identification Number on Substitute Form W-9" for
more instructions.
 
  IF BACKUP WITHHOLDING APPLIES, THE DEPOSITARY IS REQUIRED TO WITHHOLD 31% OF
ANY PAYMENTS MADE TO THE SHAREHOLDER OR OTHER PAYEE. BACKUP WITHHOLDING IS NOT
AN ADDITIONAL TAX. RATHER, THE TAX LIABILITY OF PERSONS SUBJECT TO BACKUP
WITHHOLDING WILL BE REDUCED BY THE AMOUNT OF TAX WITHHELD. IF WITHHOLDING
RESULTS IN AN OVERPAYMENT OF TAXES, A REFUND MAY BE OBTAINED FROM THE INTERNAL
REVENUE SERVICE.
 
  The box in Part 3 of the Substitute Form W-9 may be checked if the tendering
shareholder has not been issued a TIN and has applied for a TIN or intends to
apply for a TIN in the near future. If the box in Part 3 is checked, the
shareholder or other payee must also complete the Certificate of Awaiting
Taxpayer Identification Number below in order to avoid backup withholding. If
the box in Part 3 is checked and the Certificate of Awaiting Taxpayer
Identification Number is completed, but the Depositary is not provided with the
TIN within 60 days, the Depositary will withhold 31% of all payments made
thereafter until such time as a properly certified TIN is provided to the
Depositary.
 
  The shareholder is required to give the Depositary the TIN of the record
owner of the Shares and Rights or of the last transferee appearing on the
transfers attached to, or endorsed on, the Shares and Rights. If the Shares or
Rights are in more than one name or are not in the name of the actual owner,
consult the enclosed "Guidelines for Certification of Taxpayer Identification
Number on Substitute Form W-9" for additional guidance on which number to
report.
 
  10. REQUESTS FOR ASSISTANCE OR ADDITIONAL COPIES. Questions and requests for
assistance may be directed to the Dealer Manager or the Information Agent at
their respective addresses and telephone numbers set forth below. Additional
copies of the Offer to Purchase, this Letter of Transmittal and all other
tender offer materials may be obtained from the Information Agent or from
brokers, dealers, commercial banks or trust companies.
 
  11. LOST, DESTROYED OR STOLEN CERTIFICATES. If any certificate representing
Shares or Rights has been lost, destroyed or stolen, the shareholder should
promptly notify the Depositary. The shareholder will then be instructed as to
the steps that must be taken in order to replace the certificate(s). This
Letter of Transmittal and related documents cannot be processed until the
procedures for replacing lost or destroyed certificates have been followed.
<PAGE>
 
  IMPORTANT: THIS LETTER OF TRANSMITTAL (OR A FACSIMILE HEREOF), TOGETHER WITH
CERTIFICATES OR CONFIRMATION OF BOOK-ENTRY TRANSFER AND ALL OTHER REQUIRED
DOCUMENTS, OR THE NOTICE OF GUARANTEED DELIVERY, MUST BE RECEIVED BY THE
DEPOSITARY ON OR PRIOR TO THE EXPIRATION DATE.
 
                PAYER'S NAME: THE FIRST NATIONAL BANK OF BOSTON
- --------------------------------------------------------------------------------
                          PART 1--PLEASE PROVIDE YOUR  SOCIAL SECURITY NUMBER OR
 SUBSTITUTE               TIN IN THE BOX AT THE RIGHT   EMPLOYER IDENTIFICATION
                          AND CERTIFY BY SIGNING AND            NUMBER:
 FORM W-9                 DATING BELOW.                  ----------------------
                          ------------------------------------------------------
 DEPARTMENT OF            PART 2--Certification--Under penalties of perjury, I
 THE TREASURY             certify that:
 INTERNAL REVENUE
 SERVICE                  (1) The number shown on this form is my correct
                              Taxpayer Identification Number (or I am waiting
 PAYER'S REQUEST FOR          for a number to be issued to me) and
 TAXPAYER IDENTIFICATION      
 NUMBER ("TIN")           (2) I am not subject to backup withholding because:
                              (a) I am exempt from backup withholding, or (b) I 
                              have not been notified by the Internal Revenue    
                              Service (the "IRS") that I am subject to backup   
                              withholding as a result of a failure to report all
                              interest or dividends, or (c) the IRS has notified
                              me that I am no longer subject to backup          
                              withholding.                                   

                              Certification Instructions--You must cross out   
                              Item (2) above if you have been notified by the  
                              IRS that you are currently subject to backup     
                              withholding because of under-reporting interest or
                              dividends on your tax return. However, if after  
                              being notified by the IRS that you were subject to
                              backup withholding you received another          
                              notification from the IRS that you are no longer 
                              subject to backup withholding, do not cross out  
                              such Item (2).                                    
                          ------------------------------------------------------
               SIGN HERE      SIGNATURE...........................   PART 3 --
                                                                    
                              DATE............................, 19   Awaiting 
                                                                     TIN [_] 
- --------------------------------------------------------------------------------

NOTE: FAILURE TO COMPLETE AND RETURN THIS FORM MAY RESULT IN BACKUP WITHHOLDING
      OF 31% OF ANY PAYMENTS MADE TO YOU PURSUANT TO THE OFFER. PLEASE REVIEW
      THE ENCLOSED GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
      NUMBER ON SUBSTITUTE FORM W-9 FOR ADDITIONAL DETAILS.
 
       YOU MUST COMPLETE THE FOLLOWING CERTIFICATE IF YOU CHECKED THE BOX
                       IN PART 3 OF SUBSTITUTE FORM W-9.
 
- --------------------------------------------------------------------------------
             CERTIFICATE OF AWAITING TAXPAYER IDENTIFICATION NUMBER
 I certify under penalties of perjury that a Taxpayer Identification Number
 has not been issued to me, and either (1) I have mailed or delivered an
 application to receive a Taxpayer Identification Number to the appropriate
 Internal Revenue Service Center or Social Security Administration Office,
 or (2) I intend to mail or deliver an application in the near future. I
 understand that if I do not provide a Taxpayer Identification Number within
 sixty (60) days, 31% of all reportable payments made to me thereafter will
 be withheld until I provide a Taxpayer Identification Number.
 
 SIGNATURE..................                   DATE...................., 19
<PAGE>
 
                    The Information Agent for the Offer is:
 
                             D.F. KING & CO., INC.
 
                               77 Water Street 
                           New York, New York 10005 
                       (212) 269-5550 (Call Collect) or 
                          1-800-758-5378 (Toll Free)
 
                      The Dealer Manager for the Offer is:
 
                                LEHMAN BROTHERS
 
                            3 World Financial Center
                            New York, New York 10285
                        (212) 526-4089 or (212) 526-4758
                                 (Call Collect)
 
October 25, 1994

<PAGE>
 
                         NOTICE OF GUARANTEED DELIVERY
                      FOR TENDER OF SHARES OF COMMON STOCK
            (INCLUDING THE ASSOCIATED COMMON STOCK PURCHASE RIGHTS)
                                       OF
 
                          PURITAN-BENNETT CORPORATION
 
  As set forth in Section 3 of the Offer to Purchase described below, this
instrument or one substantially equivalent hereto must be used to tender shares
of Common Stock, $1.00 par value per share (the "Shares"), of Puritan-Bennett
Corporation, a Delaware corporation (the "Company"), and (unless, on or before
the Expiration Date (as defined in Section 1 of the Offer to Purchase dated
October 25, 1994 (the "Offer to Purchase")), the associated Common Stock
Purchase Rights (the "Rights") have been redeemed by the Company's Board of
Directors) the Rights pursuant to the Offer (as defined below) if certificates
for Shares and/or the Rights are not immediately available (including because
certificates for the Rights have not yet been distributed by the Company) or
the certificates for Shares or Rights and all other required documents cannot
be delivered to the Depositary prior to the Expiration Date, or if the
procedure for delivery by book-entry transfer cannot be completed on a timely
basis. This instrument may be delivered by hand or transmitted by facsimile
transmission or mail to the Depositary. This instrument is not to be used to
guarantee signatures. If a signature on a Letter of Transmittal is required to
be guaranteed by an Eligible Institution under the instructions thereto, such
signature guarantee must appear in the applicable space provided in the
signature box in the Letter of Transmittal.
 
                        The Depositary for the Offer is:
                       THE FIRST NATIONAL BANK OF BOSTON
 
         By Mail:            By Overnight Courier:            By Hand:
 
The First National Bank    The First National Bank    BancBoston Trust Company 
 of Boston                  of Boston                      of New York       
Shareholder Services       Shareholder Services            55 Broadway       
 Division                   Division                        Third Floor      
Mail Stop 45-01-19         Mail Stop 45-01-19              New York, NY       
 P. O. Box 1889            150 Royall Street                                
Boston, MA 02105           Canton, MA 02021                                  
 
                           By Facsimile Transmission:
 
                                 (617) 575-2232
                                 (617) 575-2233
 
                               For Confirmation:
                                 (617) 575-2700
 
   DELIVERY OF THIS INSTRUMENT TO AN ADDRESS OTHER THAN AS SET FORTH ABOVE OR
  TRANSMISSIONS OF INSTRUCTIONS VIA A FACSIMILE NUMBER OTHER THAN AS SET FORTH
                  ABOVE WILL NOT CONSTITUTE A VALID DELIVERY.
 
Ladies and Gentlemen:
 
  The undersigned hereby tenders to PB Acquisition Corp., a Delaware
corporation and a wholly owned subsidiary of Thermo Electron Corporation, a
Delaware corporation, upon the terms and subject to the conditions set forth in
the Offer to Purchase and in the related Letter of Transmittal (which together
constitute the "Offer"), receipt of which is hereby acknowledged, the number of
Shares, and the number of Rights, indicated below, of the Company, pursuant to
the guaranteed delivery procedures set forth in Section 3 of the Offer to
Purchase.
 
 
 
Signature(s) ________________________     Address(es) _________________________
 
Name(s) of Record Holders                 _____________________________________
                                                                       ZIP CODE
_____________________________________
        PLEASE TYPE OR PRINT              Area Code and Tel. No(s) ____________
 
Number of Shares and Rights _________     (Check one box if Shares and Rights
                                          will be tendered by book-entry
                                          transfer)
Certificate Nos. (If Available)

                                          [_] The Depository Trust Company
_____________________________________
                                          [_] Midwest Securities Trust Company
_____________________________________
                                          [_] Philadelphia Depository Trust
                                          Company
Dated ___________________________,19      Account Number ______________________
 
              THE GUARANTEE ON THE REVERSE SIDE MUST BE COMPLETED
<PAGE>
- --------------------------------------------------------------------------------
                                   GUARANTEE
                    (NOT TO BE USED FOR SIGNATURE GUARANTEE)
 
  The undersigned, a firm that is a member of a registered national securities
exchange or of the National Association of Securities Dealers, Inc. or a
commercial bank or trust company having an office, branch or agency in the
United States, (a) represents that the above named person(s) "own(s)" the
Shares and Rights, if applicable, tendered hereby within the meaning of Rule
14e-4 under the Securities Exchange Act of 1934, as amended ("Rule 14e-4"), (b)
represents that such tender of Shares and Rights, if applicable, complies with
Rule 14e-4, (c) guarantees to deliver to the Depositary either the certificates
representing all tendered Shares, in proper form for transfer, or to deliver
such Shares pursuant to the procedure for book-entry transfer into the
Depositary's account at The Depository Trust Company, the Midwest Securities
Trust Company or the Philadelphia Depository Trust Company (each a "Book-Entry
Transfer Facility"), in either case together with the Letter Of Transmittal (or
a facsimile thereof), properly completed and duly executed, with any required
signature guarantees or an Agent's Message (as defined in the Offer to
Purchase) in the case of a book-entry transfer, and any other required
documents, all within five Nasdaq National Market ("NNM") trading days after
the date hereof and (d) guarantees, if applicable, to deliver to the Depositary
either the certificates representing all tendered Rights ("Rights
Certificates"), in proper form for transfer, or to deliver such Rights pursuant
to the procedure for book-entry transfer into the Depositary's account at a
Book-Entry Transfer Facility, in either case together with, if Rights are
forwarded separately, the Letter of Transmittal (or a facsimile thereof),
properly completed and duly executed, with any required signature guarantees or
an Agent's Message in the case of a book-entry transfer, if available, and any
other required documents, all within five NNM trading days after the date
hereof or, if later, five NNM trading days after Rights Certificates are
distributed to shareholders of the Company.
 
_____________________________________   _____________________________________
            NAME OF FIRM                        AUTHORIZED SIGNATURE 
                                                 
 
_____________________________________   Name ________________________________
               ADDRESS                          PLEASE TYPE OR PRINT
                                                 
 
_____________________________________   Title _______________________________
                             ZIP CODE
 
Area Code and Tel. No. ______________   Dated _________________________ , 19
 

NOTE: DO NOT SEND CERTIFICATES FOR SHARES OR RIGHTS WITH THIS NOTICE.
      CERTIFICATES SHOULD BE SENT WITH YOUR LETTER OF TRANSMITTAL.
- --------------------------------------------------------------------------------

<PAGE>
 
                           OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
            (INCLUDING THE ASSOCIATED COMMON STOCK PURCHASE RIGHTS)
 
                                       OF
 
                          PURITAN-BENNETT CORPORATION
 
                                       AT
 
                              $24.50 NET PER SHARE
 
                                       BY
 
                              PB ACQUISITION CORP.
                          A WHOLLY OWNED SUBSIDIARY OF
 
                          THERMO ELECTRON CORPORATION
 
- --------------------------------------------------------------------------------
  THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
       TIME, ON TUESDAY, NOVEMBER 22, 1994, UNLESS THE OFFER IS EXTENDED.
- --------------------------------------------------------------------------------
                                                                October 25, 1994
 
To Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees:
 
  We have been appointed by PB Acquisition Corp., a Delaware corporation (the
"Purchaser") and a wholly owned subsidiary of Thermo Electron Corporation, a
Delaware corporation (the "Parent"), to act as Dealer Manager in connection
with the Purchaser's offer to purchase all of the outstanding shares of Common
Stock, par value $1.00 per share (the "Shares"), of Puritan-Bennett
Corporation, a Delaware corporation (the "Company"), and (unless, on or before
the Expiration Date (as defined in the Offer to Purchase), the associated
Common Stock Purchase Rights (the "Rights") have been redeemed by the Company's
Board of Directors) the Rights issued pursuant to the Rights Agreement, dated
as of May 2, 1989 (the "Rights Agreement"), between the Company and United
Missouri Bank of Kansas City, N.A., as Rights Agent, at a purchase price of
$24.50 per Share (and associated Right), net to the seller in cash, without
interest thereon, upon the terms and subject to the conditions set forth in the
Offer to Purchase, dated October 25, 1994 (the "Offer to Purchase") and in the
related Letter of Transmittal (which together constitute the "Offer") enclosed
herewith. Unless the context otherwise requires, all references to "Shares"
shall be deemed to refer also to the Rights, and all references to the "Rights"
shall be deemed to include all benefits that may inure to the shareholders of
the Company or to holders of Rights pursuant to the Rights Agreement.
 
  Unless, on or before the Expiration Date, the Rights have been redeemed by
the Company's Board of Directors, holders of Shares will be required to tender
one Right for each Share tendered in order to effect a valid tender of such
Share. If separate certificates for the Rights are not issued, a tender of
Shares will also constitute a tender of the associated Rights. If the
Distribution Date (as defined in the Offer to Purchase) has occurred and
certificates representing Rights (the "Rights Certificates") have been
distributed to holders of Shares prior to the date of tender pursuant to the
Offer, in order for Rights (and the corresponding Shares) to be validly
tendered, Rights Certificates representing a number of Rights equal to the
number of Shares being tendered must be delivered to the Depositary (as defined
below) or, if available, a Book-Entry Confirmation (as defined in the Offer to
Purchase) must be received by the Depositary with respect thereto. If the
Distribution Date has occurred and Rights Certificates have not been
distributed prior to the time Shares are tendered pursuant to the Offer, Rights
may be tendered prior to a shareholder receiving Rights Certificates by use of
the guaranteed delivery procedures described in the Offer to Purchase. In any
case, a tender of Shares without Rights Certificates constitutes an agreement
by the tendering shareholder to deliver
<PAGE>
 
Rights Certificates representing a number of Rights equal to the number of
Shares tendered pursuant to the Offer to the Depositary within five business
days after the date such Rights Certificates are distributed. Holders of Shares
and Rights whose certificates for Shares (the "Share Certificates") and, if
applicable, Rights Certificates, are not immediately available or who cannot
deliver their Share Certificates or, if applicable, their Rights Certificates,
and all other required documents to reach the Depositary on or prior to the
Expiration Date, or who cannot complete the procedures for delivery by book-
entry transfer on a timely basis, may tender their Shares and Rights according
to the guaranteed delivery procedures set forth in Section 3 of the Offer to
Purchase.
 
  The Offer is conditioned upon, among other things: (1) there being validly
tendered and not withdrawn prior to the expiration of the Offer that number of
Shares which, together with the Shares beneficially owned by the Purchaser and
the Parent, constitutes at least a majority of the Shares outstanding
(determined on a fully diluted basis); (2) the Rights having been redeemed, or
made inapplicable to the Offer and the proposed Merger described in the Offer
to Purchase, by the Company's Board of Directors; (3) the Purchaser being
satisfied, in its sole discretion, that Section 203 of the Delaware General
Corporation Law is inapplicable to the proposed Merger described in the Offer
to Purchase; and (4) the Purchaser being satisfied, in its sole discretion,
that the supermajority voting requirement contained in Article Fifth of the
Company's Articles of Incorporation is inapplicable to the proposed Merger
described in the Offer to Purchase. Satisfaction of one or more of the
foregoing conditions will require the approval of the Offer and the proposed
Merger described in the Offer to Purchase by the Board of Directors of the
Company. The Offer is also subject to certain other terms and conditions
contained in the Offer to Purchase. See the Introduction and Sections 1 and 14
of the Offer to Purchase. The Offer is not conditioned upon the Purchaser
obtaining financing.
 
  Enclosed herewith for your information and forwarding to your clients for
whose accounts you hold Shares registered in your name or in the name of your
nominee are copies of the following documents:
 
    1. The Offer to Purchase, dated October 25, 1994.
 
    2. The green Letter of Transmittal to tender Shares for your use and for
  the information of your clients. Facsimile copies of the Letter of
  Transmittal may be used to tender Shares.
 
    3. The yellow Notice of Guaranteed Delivery for Shares and Rights to be
  used to accept the Offer if Share Certificates or Rights Certificates are
  not immediately available or if such certificates and all other required
  documents cannot be delivered to The First National Bank of Boston (the
  "Depositary") by the Expiration Date or if the procedures for book-entry
  transfer cannot be completed on a timely basis.
 
    4. A gray printed form of letter which may be sent to your clients for
  whose accounts you hold Shares registered in your name or in the name of
  your nominee, with space provided for obtaining such clients' instructions
  with regard to the Offer.
 
    5. Guidelines for Certification of Taxpayer Identification Number on
  Substitute Form W-9.
 
    6. A return envelope addressed to the Depositary.
 
  YOUR PROMPT ACTION IS REQUESTED. WE URGE YOU TO CONTACT YOUR CLIENTS AS
PROMPTLY AS POSSIBLE. PLEASE NOTE THAT THE OFFER AND WITHDRAWAL RIGHTS WILL
EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON TUESDAY, NOVEMBER 22, 1994,
UNLESS THE OFFER IS EXTENDED.
 
  In order for Shares to be validly tendered pursuant to the Offer, (i) a duly
executed and properly completed Letter of Transmittal (or a facsimile thereof)
together with any required signature guarantees, or an Agent's Message (as
defined in the Offer to Purchase) in connection with a book-entry delivery of
Shares and Rights, and other documents required by the Letter of Transmittal
must be received by the Depositary on or prior to the Expiration Date, and (ii)
either Share Certificates and Rights Certificates, if applicable, representing
tendered Shares and Rights must be received by the Depositary, or such Shares
and Rights must be tendered by book-entry transfer into the Depositary's
account maintained at one of the Book-Entry Transfer Facilities (as described
in the Offer to Purchase), and Book-Entry Confirmation must be received by
 
                                       2
<PAGE>
 
the Depositary, all in accordance with the instructions set forth in the Letter
of Transmittal and the Offer to Purchase.
 
  If a shareholder desires to tender Shares and Rights pursuant to the Offer
and such shareholder's Share Certificates or Rights Certificates are not
immediately available (including because Rights Certificates have not yet been
distributed by the Company), or such shareholder cannot deliver the Share
Certificates or Rights Certificates and all other required documents to reach
the Depositary on or prior to the Expiration Date, or such shareholder cannot
complete the procedure for delivery by book-entry transfer on a timely basis,
such Shares and Rights may nevertheless be tendered by following the guaranteed
delivery procedures specified in Section 3 of the Offer to Purchase.
 
  The Purchaser will not pay any fees or commissions to any broker or dealer or
any other person for soliciting tenders of Shares pursuant to the Offer (other
than to the Dealer Manager and D.F. King & Co., Inc. (the "Information Agent")
(as described in the Offer to Purchase)). The Purchaser will, however, upon
request, reimburse you for customary mailing and handling expenses incurred by
you in forwarding any of the enclosed materials to your clients. The Purchaser
will pay or cause to be paid any stock transfer taxes payable on the transfer
and sale of Shares to the Purchaser pursuant to the Offer, except as otherwise
provided in Instruction 6 of the Letter of Transmittal.
 
  Any inquiries you may have with respect to the Offer should be addressed to
Lehman Brothers Inc., the Dealer Manager, or to the Information Agent, at their
respective addresses and telephone numbers set forth on the back cover of the
Offer to Purchase. Additional copies of the enclosed material may be obtained
from the Information Agent.
 
                                          Very truly yours,
 
                                          Lehman Brothers Inc.
 
  NOTHING CONTAINED HEREIN OR IN THE ENCLOSED DOCUMENTS SHALL CONSTITUTE YOU OR
ANY OTHER PERSON THE AGENT OF THE PURCHASER, THE PARENT, THE DEALER MANAGER,
THE COMPANY, THE DEPOSITARY OR THE INFORMATION AGENT, OR ANY AFFILIATE OF ANY
OF THEM, OR AUTHORIZE YOU OR ANY OTHER PERSON TO MAKE ANY STATEMENT OR USE ANY
DOCUMENT ON BEHALF OF ANY OF THEM IN CONNECTION WITH THE OFFER OTHER THAN THE
ENCLOSED DOCUMENTS AND THE STATEMENTS CONTAINED THEREIN.
 
                                       3

<PAGE>
 
                           OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
            (INCLUDING THE ASSOCIATED COMMON STOCK PURCHASE RIGHTS)
 
                                       OF
 
                          PURITAN-BENNETT CORPORATION
 
                                       AT
 
                              $24.50 NET PER SHARE
 
                                       BY
 
                              PB ACQUISITION CORP.
                          A WHOLLY OWNED SUBSIDIARY OF
 
                          THERMO ELECTRON CORPORATION
 
- --------------------------------------------------------------------------------
  THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
       TIME, ON TUESDAY, NOVEMBER 22, 1994, UNLESS THE OFFER IS EXTENDED.
- --------------------------------------------------------------------------------
 
To Our Clients:
 
  Enclosed for your consideration is an Offer to Purchase dated October 25,
1994 (the "Offer to Purchase") and the related Letter of Transmittal relating
to an offer by PB Acquisition Corp., a Delaware corporation (the "Purchaser")
and a wholly owned subsidiary of Thermo Electron Corporation, a Delaware
corporation (the "Parent"), to purchase all of the outstanding shares of Common
Stock, $1.00 par value per share (the "Shares"), of Puritan-Bennett
Corporation, a Delaware corporation (the "Company"), and (unless on or before
the Expiration Date (as defined below), the associated Common Stock Purchase
Rights (the "Rights") have been redeemed by the Company's Board of Directors)
the Rights issued pursuant to the Rights Agreement, dated as of May 2, 1989
(the "Rights Agreement"), between the Company and United Missouri Bank of
Kansas City, N.A., as Rights Agent, at a purchase price of $24.50 per Share
(and associated Right), net to the seller in cash, without interest thereon,
upon the terms and subject to the conditions set forth in the Offer to Purchase
and in the related Letter of Transmittal (which together constitute the
"Offer"). Unless the context requires otherwise, all references to "Shares"
shall be deemed to refer also to the Rights, and all references to "Rights"
shall be deemed to include all benefits that may inure to the shareholders of
the Company or to holders of the Rights pursuant to the Rights Agreement.
 
  We are the holder of record of Shares held by us for your account. A tender
of such Shares can be made only by us as the holder of record and pursuant to
your instructions. The Letter of Transmittal is furnished to you for your
information only and cannot be used by you to tender Shares held by us for your
account.
 
  Unless, on or before the Expiration Date, the Rights have been redeemed by
the Company's Board of Directors, holders of Shares will be required to tender
one Right for each Share tendered in order to effect a valid transfer of such
Share. If separate certificates for the Rights are not issued, a tender of
Shares will also constitute a tender of the associated Rights. If the
Distribution Date (as defined in the Offer to Purchase) has occurred and
certificates representing Rights (the "Rights Certificates") have been
distributed to holders of Shares prior to the date of tender pursuant to the
Offer, in order for Rights (and the corresponding Shares) to be validly
tendered, Rights Certificates representing a number of Rights equal to the
number of Shares being tendered must be delivered to the Depositary (as defined
below) or, if available, a Book-Entry Confirmation (as defined in the Offer to
Purchase) must be received by the Depositary with respect thereto. If the
Distribution Date has occurred and Rights Certificates have not been
distributed prior to the time Shares are tendered pursuant to the Offer, Rights
may be tendered prior to a shareholder receiving Rights Certificates by use of
the guaranteed delivery procedures described in the Offer to Purchase. In any
case, a tender of Shares without Rights Certificates constitutes an agreement
by the tendering shareholder to deliver Rights Certificates representing a
number of Rights equal to the number of Shares tendered pursuant to the Offer
to the Depositary within five business days after such Rights Certificates are
distributed.
 
<PAGE>
 
  We request instructions as to whether you wish to have us tender on your
behalf any or all of such Shares held by us for your account, pursuant to the
terms and subject to the conditions set forth in the Offer to Purchase. Your
instructions to tender Shares held by us for your account will also constitute
a direction to us to tender a number of Rights held by us for your account
equal to the number of Shares tendered.
 
  Your attention is directed to the following:
 
    1. The tender price is $24.50 per share, net to the seller in cash.
 
    2. The Offer is made for all of the outstanding Shares.
 
    3. The Offer and withdrawal rights will expire at 12:00 midnight, New
  York City time, on Tuesday, November 22, 1994, unless the Offer is
  extended.
 
    4. The Offer is conditioned upon, among other things: (1) there being
  validly tendered and not withdrawn prior to the expiration of the Offer
  that number of Shares which, together with the Shares beneficially owned by
  the Purchaser and the Parent, constitutes at least a majority of the Shares
  outstanding (determined on a fully diluted basis); (2) the Rights having
  been redeemed, or made inapplicable to the Offer and the proposed Merger
  described in the Offer to Purchase, by the Company's Board of Directors;
  (3) the Purchaser being satisfied, in its sole discretion, that Section 203
  of the Delaware General Corporation Law is inapplicable to the proposed
  Merger described in the Offer to Purchase; and (4) the Purchaser being
  satisfied, in its sole discretion, that the supermajority voting
  requirement contained in Article Fifth of the Company's Articles of
  Incorporation is inapplicable to the proposed Merger described in the Offer
  to Purchase. Satisfaction of one or more of the foregoing conditions will
  require the approval of the Offer and the proposed Merger described in the
  Offer to Purchase by the Board of Directors of the Company. The Offer is
  also subject to certain other terms and conditions contained in the Offer
  to Purchase. See the Introduction and Sections 1 and 14 of the Offer to
  Purchase. The Offer is not conditioned upon the Purchaser obtaining
  financing.
 
    5. Tendering shareholders will not be obligated to pay brokerage fees or
  commissions or, except as set forth in Instruction 6 of the Letter of
  Transmittal, stock transfer taxes on the transfer and sale of Shares and
  Rights pursuant to the Offer.
 
    6. In all cases, payment for Shares tendered and accepted for payment
  pursuant to the Offer will be made only after timely receipt by The First
  National Bank of Boston (the "Depositary") of (i) Share Certificates and,
  if applicable, Rights Certificates, or timely confirmation of a book-entry
  transfer of such Shares and Rights, if applicable, into the Depositary's
  account at The Depository Trust Company, the Midwest Securities Trust
  Company or the Philadelphia Depository Trust Company (each, a "Book-Entry
  Transfer Facility") pursuant to the procedures set forth in Section 3 of
  the Offer to Purchase, (ii) the Letter of Transmittal (or a facsimile
  thereof), properly completed and duly executed, with any required signature
  guarantees, or an Agent's Message (as defined in the Offer to Purchase),
  and (iii) any other documents required by the Letter of Transmittal.
  Accordingly, payment might not be made to all tendering shareholders at the
  same time and will depend upon when Share Certificates and, if applicable,
  Rights Certificates, or confirmations of book-entry transfer of such Shares
  or Rights, if available, are received into the Depositary's account at a
  Book-Entry Transfer Facility.
 
  The Offer is being made solely by the Offer to Purchase and the related
Letter of Transmittal and is being made to all holders of Shares. The Purchaser
is not aware of any state where the making of the Offer is prohibited by
administrative or judicial action pursuant to any valid state statute. If the
Purchaser becomes aware of any valid state statute prohibiting the making of
the Offer or the acceptance of Shares pursuant thereto, the Purchaser will make
a good faith effort to comply with any such state statute or seek to have such
statute declared inapplicable to the Offer. If, after such good faith effort,
the Purchaser cannot comply with such state statute, the Offer will not be made
to nor will tenders be accepted from or on behalf of the holders of Shares in
such state. In any jurisdiction where the securities, blue sky or other laws
require the Offer to be made by a licensed broker or dealer, the Offer shall be
deemed to be made on behalf of the Purchaser by the Dealer Manager or one or
more registered brokers or dealers that are licensed under the laws of such
jurisdiction.
 
  If you wish to have us tender any or all of the Shares held by us for your
account, please instruct us by completing, executing and returning to us the
instruction form contained in this letter. If you authorize a tender of your
Shares, all such Shares will be tendered unless otherwise specified in such
instruction form. Your instructions should be forwarded to us in ample time to
permit us to submit a tender on your behalf prior to the expiration of the
Offer.
 
                                       2
<PAGE>
 
          INSTRUCTIONS WITH RESPECT TO THE OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
            (INCLUDING THE ASSOCIATED COMMON STOCK PURCHASE RIGHTS)
                                       OF
                          PURITAN-BENNETT CORPORATION
 
  The undersigned acknowledge(s) receipt of your letter enclosing the Offer to
Purchase dated October 25, 1994 (the "Offer to Purchase") and the related
Letter of Transmittal pursuant to an offer by PB Acquisition Corp., a Delaware
corporation and a wholly owned subsidiary of Thermo Electron Corporation, a
Delaware corporation, to purchase all of the outstanding shares of Common
Stock, $1.00 par value per share (the "Shares"), of Puritan-Bennett
Corporation, a Delaware corporation, and (unless, on or before the Expiration
Date (as defined in the Offer to Purchase), the associated Common Stock
Purchase Rights (the "Rights") have been redeemed by the Company's Board of
Directors), the Rights.
 
  This will instruct you to tender the number of Shares and Rights indicated
below (or, if no number is indicated below, all Shares and Rights) which are
held by you for the account of the undersigned, upon the terms and subject to
the conditions set forth in the Offer to Purchase and in the related Letter of
Transmittal furnished to the undersigned.
 
- --------------------------------------------------------------------------------
 Number of Shares (and Rights) to be Tendered*: ____________ Shares (and Rights)
 
 Dated: _____________, 19
- --------------------------------------------------------------------------------

- --------------------------------------------------------------------------------
                                    SIGN HERE
 
 Signature(s): _______________________________________________________________
 
 Please print name(s): _______________________________________________________
 
 Address: ____________________________________________________________________
 
 Area Code and 
 Telephone Number: ___________________________________________________________
 
 Tax Identification or 
 Social Security Number: _____________________________________________________
- --------------------------------------------------------------------------------
- --------
* Unless otherwise indicated, it will be assumed that all of the Shares (and
  Rights) held by us for your account are to be tendered.
 
                                       3

<PAGE>
 
            GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
                         NUMBER ON SUBSTITUTE FORM W-9
 
GUIDELINES FOR DETERMINING THE PROPER IDENTIFICATION NUMBER TO GIVE THE PAYER.--
Social Security numbers have nine digits separated by two hyphens: i.e. 000-00-
0000. Employer identification numbers have nine digits separated by only one
hyphen: i.e. 00-0000000. The table below will help determine the number to give
the payer.

<TABLE> 
<CAPTION> 
 
- ----------------------------------------------        
                              GIVE THE
FOR THIS TYPE OF ACCOUNT:     SOCIAL SECURITY
                              NUMBER OF--
- ----------------------------------------------
<S>                           <C>
1. An individual's account    The individual

2. Two or more individuals    The actual owner
   (joint account)            of the account
                              or, if combined
                              funds, any one
                              of the
                              individuals (1)

3. Husband and wife (joint    The actual owner
   account)                   of the account
                              or, if joint
                              funds, either
                              person(1)
                             
4. Custodian account of a     The minor(2)
   minor (Uniform Gift to    
   Minors Act)               
                             
5. Adult and minor (joint     The adult or, if
   account)                   the minor is the
                              only
                              contributor, the
                              minor(1)
                             
6. Account in the name of     The ward, minor,
   guardian or committee      or incompetent
   for a designated ward,     person(3)
   minor, or incompetent     
   person                    
                             
7. a. The usual revocable     The grantor-
    savings trust account     trustee(1)
    (grantor is also
    trustee)
   b. So-called trust account The actual
    that is not a legal or    owner(1)
    valid trust under State    
    law                        

8. Sole proprietorship        The owner(4)
   account                     
- ----------------------------------------------
</TABLE>

<TABLE>
<CAPTION>
- ----------------------------------------------
                             GIVE THE EMPLOYER
FOR THIS TYPE OF ACCOUNT:    IDENTIFICATION
                             NUMBER OF--
- ----------------------------------------------
<S>                          <C>
 9. A valid trust, estate,   The legal entity
    or pension trust         (Do not furnish
                             the identifying
                             number of the
                             personal
                             representative
                             or trustee
                             unless the legal
                             entity itself is
                             not designated
                             in the account
                             title.)(5)

10. Corporate account        The corporation

11. Religious, charitable,   The organization
    or educational
    organization account

12. Partnership account      The partnership
    held in the name of the
    business

13. Association, club, or    The organization
    other tax-exempt
    organization

14. A broker or registered   The broker or
    nominee                  nominee

15. Account with the         The public
    Department of            entity
    Agriculture in the name
    of a public entity
    (such as a State or
    local government,
    school district, or
    prison) that receives
    agricultural program
    payments
- ----------------------------------------------
</TABLE>
 
(1) List first and circle the name of the person whose number you furnish.
(2) Circle the minor's name and furnish the minor's social security number.
(3) Circle the ward's, minor's or incompetent person's name and furnish such
    person's social security number.
(4) Show the name of the owner.
(5) List first and circle the name of the legal trust, estate, or pension
    trust.
 
NOTE: If no name is circled when there is more than one name, the number will
      be considered to be that of the first name listed.
<PAGE>
 
            GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
                         NUMBER ON SUBSTITUTE FORM W-9
                                    PAGE 2
OBTAINING A NUMBER
If you do not have a taxpayer identification number or you do not know your
number, obtain Form SS-5, Application for a Social Security Number Card, or
Form SS-4, Application for Employer Identification Number, at the local office
of the Social Security Administration or the Internal Revenue Service and ap-
ply for a number.
 
PAYEES EXEMPT FROM BACKUP WITHHOLDING
Payees specifically exempted from backup withholding on ALL payments include
the following:
 . A corporation.
 . A financial institution.
 . An organization exempt from tax under section 501(a), or an individual re-
   tirement plan.
 . The United States or any agency or instrumentality thereof.
 . A State, the District of Columbia, a possession of the United States, or
   any subdivision or instrumentality thereof.
 . A foreign government, a political subdivision of a foreign government, or
   any agency or instrumentality thereof.
 . An international organization or any agency, or instrumentality thereof.
 . A registered dealer in securities or commodities registered in the U.S. or
   a possession of the U.S.
 . A real estate investment trust.
 . A common trust fund operated by a bank under section 584(a).
 . An exempt charitable remainder trust, or a non-exempt trust described in
   section 4947(a)(1).
 . An entity registered at all times under the investment Company Act of
   1940.
 . A foreign central bank of issue.
   Payments of dividends and patronage dividends not generally subject to
   backup withholding include the following:
 . Payments to nonresident aliens subject to withholding under section 1441.
 . Payments to partnerships not engaged in a trade or business in the U.S.
   and which have at least one nonresident partner.
 . Payments of patronage dividends where the amount received is not paid in
   money.
 . Payments made by certain foreign organizations.
 . Payments made to a nominee.
 Payments of interest not generally subject to backup withholding include the
following:
 . Payments of interest on obligations issued by individuals. Note: You may
   be subject to backup withholding if this interest is $600 or more and is
   paid in the course of the payer's trade or business and you have not pro-
   vided your correct taxpayer identification number to the payer.
 . Payments of tax-exempt interest (including exempt-interest dividends under
   section 852).
 . Payments described in section 6049(b)(5) to nonresident aliens.
 . Payments on tax-free covenant bonds under section 1451.
 . Payments made by certain foreign organizations.
 . Payments made to a nominee.
Exempt payees described above should file Form W-9 to avoid possible erroneous
backup withholding. FILE THIS FORM WITH THE PAYER, FURNISH YOUR TAXPAYER IDEN-
TIFICATION NUMBER, WRITE "EXEMPT" ON THE FACE OF THE FORM, AND RETURN IT TO
THE PAYER. IF THE PAYMENTS ARE INTEREST, DIVIDENDS, OR PATRONAGE DIVIDENDS,
ALSO SIGN AND DATE THE FORM.
 Certain payments other than interest, dividends, and patronage dividends,
that are not subject to information reporting are also not subject to backup
withholding. For details, see the regulations under sections 6041, 6041A(a),
6045, and 6050A.
PRIVACY ACT NOTICE.--Section 6109 requires most recipients of dividend, inter-
est, or other payments to give taxpayer identification numbers to payers who
must report the payments to IRS. IRS uses the numbers for identification pur-
poses. Payers must be given the numbers whether or not recipients are required
to file tax returns. Beginning January 1, 1984, payers must generally withhold
20% of taxable interest, dividend, and certain other payments to a payee who
does not furnish a taxpayer identification number to a payer. Certain penal-
ties may also apply.
 
PENALTIES
(1) PENALTY FOR FAILURE TO FURNISH TAXPAYER IDENTIFICATION NUMBER.--If you
fail to furnish your taxpayer identification number to a payer, you are sub-
ject to a penalty of $50 for each such failure unless your failure is due to
reasonable cause and not to willful neglect.
(2) FAILURE TO REPORT CERTAIN DIVIDEND AND INTEREST PAYMENTS.--If you fail to
include any portion of an includible payment for interest, dividends, or pat-
ronage dividends in gross income, such failure will be treated as being due to
negligence and will be subject to a penalty of 5% on any portion of an under-
payment attributable to that failure unless there is clear and convincing evi-
dence to the contrary.
(3) CIVIL PENALTY FOR FALSE INFORMATION WITH RESPECT TO WITHHOLDING.--If you
make a false statement with no reasonable basis which results in no imposition
of backup withholding, you are subject to a penalty of $500.
(4) CRIMINAL PENALTY FOR FALSIFYING INFORMATION.--Falsifying certifications or
affirmations may subject you to criminal penalties including fines and/or im-
prisonment.
FOR ADDITIONAL INFORMATION CONTACT YOUR TAX CONSULTANT OR THE INTERNAL REVENUE
SERVICE.

<PAGE>
 
This announcement is neither an offer to purchase nor a solicitation of an
offer to sell Shares. The Offer is being made solely by the Offer to Purchase
dated October 25, 1994 and the related Letter of Transmittal and is being made
to all holders of Shares. The Offer is not being made to (nor will tenders be
accepted from or on behalf of) holders of Shares in any jurisdiction in which
the making of the Offer or the acceptance thereof would not be in compliance
with the laws of such jurisdiction. In any jurisdiction where the securities,
blue sky or other laws require the Offer to be made by a licensed broker or
dealer, the Offer shall be deemed to be made on behalf of PB Acquisition Corp.
by Lehman Brothers Inc. or one or more registered brokers or dealers that are
licensed under the laws of such jurisdiction.

                     Notice of Offer to Purchase for Cash

                    All Outstanding Shares of Common Stock
            (Including the Associated Common Stock Purchase Rights)

                                      of

                          Puritan-Bennett Corporation

                                      at

                             $24.50 Net Per Share

                                      by

                             PB Acquisition Corp.

                         a wholly owned subsidiary of

                          Thermo Electron Corporation

     PB Acquisition Corp., a Delaware corporation (the "Purchaser") and a wholly
owned subsidiary of Thermo Electron Corporation, a Delaware corporation (the
"Parent"), hereby offers to purchase all of the outstanding shares of Common
Stock, $1.00 par value per share (the "Shares"), of Puritan-Bennett
Corporation, a Delaware corporation (the "Company"), and (unless, on or before
the Expiration Date (as defined below), the associated Common Stock Purchase
Rights (the "Rights") have been redeemed by the Company's Board of Directors)
the Rights issued pursuant to the Rights Agreement, dated as of May 2, 1989,
between the Company and United Missouri Bank of Kansas City, N.A., as Rights
Agent (the "Rights Agreement"), at a purchase price of $24.50 per Share (and
associated Right), net to the seller in cash, without interest thereon, upon
the terms and subject to the conditions set forth in the Offer to Purchase
dated October 25, 1994 (the "Offer to Purchase") and in the related Letter of
Transmittal (which together constitute the "Offer"). Unless the context
requires otherwise, all references to "Shares" shall be deemed to refer also to
the Rights, and all references to "Rights" shall be deemed to include all
benefits that may inure to the shareholders of the Company or to holders of the
Rights pursuant to the Rights Agreement.

- -----------------------------------------------------------------------------
THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
TIME, ON TUESDAY, NOVEMBER 22, 1994, UNLESS THE OFFER IS EXTENDED.
- -----------------------------------------------------------------------------

     THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS: (1) THERE BEING VALIDLY
TENDERED AND NOT WITHDRAWN PRIOR TO THE EXPIRATION OF THE OFFER THAT NUMBER OF
SHARES WHICH, TOGETHER WITH THE SHARES BENEFICIALLY OWNED BY THE PURCHASER AND
THE PARENT, CONSTITUTES AT LEAST A MAJORITY OF THE SHARES OUTSTANDING
(DETERMINED ON A FULLY DILUTED BASIS); (2) THE RIGHTS HAVING BEEN REDEEMED, OR

<PAGE>
 
MADE INAPPLICABLE TO THE OFFER AND THE MERGER (AS DEFINED BELOW) DESCRIBED IN
THE OFFER TO PURCHASE, BY THE COMPANY'S BOARD OF DIRECTORS; (3) THE PURCHASER
BEING SATISFIED IN ITS SOLE DISCRETION, THAT SECTION 203 OF THE DELAWARE
GENERAL CORPORATION LAW IS INAPPLICABLE TO THE MERGER DESCRIBED IN THE OFFER TO
PURCHASE; AND (4) THE PURCHASER BEING SATISFIED, IN ITS SOLE DISCRETION, THAT
THE SUPERMAJORITY VOTING REQUIREMENT CONTAINED IN ARTICLE FIFTH OF THE
COMPANY'S ARTICLES OF INCORPORATION IS INAPPLICABLE TO THE MERGER DESCRIBED IN
THE OFFER TO PURCHASE. SATISFACTION OF ONE OR MORE OF THE FOREGOING CONDITIONS
WILL REQUIRE THE APPROVAL OF THE OFFER AND THE MERGER DESCRIBED IN THE OFFER TO
PURCHASE BY THE BOARD OF DIRECTORS OF THE COMPANY. THE OFFER IS ALSO SUBJECT TO
CERTAIN OTHER TERMS AND CONDITIONS CONTAINED IN THE OFFER TO PURCHASE. SEE THE
INTRODUCTION AND SECTIONS 1 AND 14 OF THE OFFER TO PURCHASE. THE OFFER IS NOT
CONDITIONED UPON THE PURCHASER OBTAINING FINANCING.

     The purpose of the Offer and the Merger is to acquire control of, and the
entire equity interest in, the Company. The Offer, as the first step in the
acquisition of the Company, is intended to facilitate the acquisition of all
outstanding Shares. As soon as practicable following consummation of the Offer,
the Purchaser intends to seek the maximum representation obtainable on the
Company's Board of Directors and to propose, and to seek to have the Company
consummate as soon as practicable after consummation of the Offer, a merger or
similar business combination with the Purchaser or another direct or indirect
wholly owned subsidiary of the Parent (the "Merger"), pursuant to which each
then outstanding Share (other than (1) Shares held by the Parent, the Purchaser
or any other direct or indirect wholly owned subsidiary of the Parent, (2)
Shares held in the treasury of the Company and (3) Shares held by shareholders
who properly exercise appraisal rights under Section 262 of the Delaware
General Corporation Law) would be converted into the right to receive in cash
the same price per Share paid by the Purchaser in the Offer, without interest.
The consummation of the Merger would be subject to a number of factors
(including satisfaction of various conditions) discussed in the Introduction
and in Sections 11 and 14 of the Offer to Purchase. Section 11 of the Offer to
Purchase also discusses certain appraisal rights available to shareholders upon
consummation of the Merger.

    Unless, on or before the Expiration Date, the Rights have been redeemed by
the Company's Board of Directors, holders of Shares will be required to tender
one Right for each Share tendered in order to effect a valid tender of such
Share. If separate certificates for the Rights are not issued, a tender of
Shares will also constitute a tender of the associated Rights. If the
Distribution Date (as defined in the Offer to Purchase) has occurred and
certificates representing Rights (the "Rights Certificates") have been
distributed to holders of Shares prior to the date of tender pursuant to the
Offer, in order for Rights (and the corresponding Shares) to be validly
tendered, Rights Certificates representing a number of Rights equal to the
number of Shares being tendered must be delivered to The First National Bank of
Boston (the "Depositary") or, if available, a confirmation of book-entry
transfer (a "Book-Entry Confirmation") must be received by the Depositary with
respect thereto. If the Distribution Date has occurred and Rights Certificates
have not been distributed prior to the time Shares are tendered pursuant to the
Offer, Rights may be tendered prior to a shareholder receiving Rights
Certificates by use of the
<PAGE>
 
guaranteed delivery procedures described in Section 3 of the Offer to Purchase.
In any case, a tender of Shares without Rights Certificates constitutes an
agreement by the tendering shareholder to deliver Rights Certificates
representing a number of Rights equal to the number of Shares tendered pursuant
to the Offer to the Depositary within five business days after the date such
Rights Certificates are distributed. Unless, on or before the Expiration Date,
the Rights have been redeemed by the Company's Board of Directors, the Purchaser
reserves the right to require that the Depositary receive such Rights
Certificates, or Book-Entry Confirmation, if available, with respect to such
Rights, prior to accepting the related Shares for payment. In that event,
payment for Shares tendered and accepted for payment pursuant to the Offer will
be made only after timely receipt by the Depositary of, among other things,
Rights Certificates, or Book-Entry Confirmation, if available, with respect to
such Rights, if Rights Certificates have been distributed to holders of Shares.

     For purposes of the Offer, the Purchaser will be deemed to have accepted 
for payment (and thereby purchased) Shares validly tendered and not properly
withdrawn as, if and when the Purchaser gives oral or written notice to the
Depositary of the Purchaser's acceptance for payment of such Shares pursuant to
the Offer. Upon the terms and subject to the conditions of the Offer, payment
for Shares so accepted for payment pursuant to the Offer will be made by deposit
of the aggregate purchase price therefor with the Depositary, which will act as
agent for tendering shareholders for the purpose of receiving payment from the
Purchaser and transmitting such payment to shareholders whose Shares have been
accepted for payment. Under no circumstances will interest on the purchase price
for Shares be paid by the Purchaser, regardless of any delay in making such
payment. In all cases, payment for Shares tendered and accepted for payment
pursuant to the Offer will be made only after timely receipt by the Depositary
of (1) certificates representing shares ("Share Certificates") and, if
applicable, Rights Certificates, or timely confirmation of a book-entry transfer
of such Shares and Rights, if applicable, into the Depositary's account at The
Depository Trust Company, the Midwest Securities Trust Company or the
Philadelphia Depository Trust Company (each a "Book-Entry Transfer Facility")
pursuant to the procedures set forth in Section 3 of the Offer to Purchase, (2)
the Letter of Transmittal (or a facsimile thereof), properly completed and duly
executed, with any required signature guarantees, or an Agent's Message (as
defined in Section 2 of the Offer to Purchase) in connection with a book-entry
transfer, and (3) any other documents required by the Letter of Transmittal.

     The Purchaser expressly reserves the right, in its sole discretion, at any
time and from time to time, to extend the period during which the Offer is open
for any reason, including the occurrence of any of the conditions specified in
Section 14 of the Offer to Purchase, and thereby delay acceptance for payment
of, or payment for, any Shares, by giving oral or written notice of such
extension to the Depositary. Any such extension will be followed as promptly as
practicable by public announcement thereof, such announcement to be made no
later than 9:00 a.m., New York City time, on the next business day after the
previously scheduled Expiration Date.

     The term "Expiration Date" means 12:00 midnight, New York City time, on
Tuesday, November 22, 1994, unless and until the Purchaser, in its sole
discretion, shall have extended the period during which the Offer is open, in
which event the term "Expiration 

<PAGE>
 
     Date" shall mean the latest time and date at which the Offer, as so 
extended by the Purchaser, shall expire.

     Except as otherwise provided in Section 4 of the Offer to Purchase, tenders
of Shares and Rights made pursuant to the Offer are irrevocable, except that
Shares and Rights tendered pursuant to the Offer may be withdrawn at any time
on or prior to the Expiration Date and, unless theretofore accepted for payment
by the Purchaser pursuant to the Offer, may also be withdrawn at any time after
December 23, 1994 (or such later date as may apply in case the Offer is
extended). In order for a withdrawal to be effective, a written, telegraphic or
facsimile transmission notice of withdrawal must be timely received by the
Depositary at one of its addresses set forth on the back cover of the Offer to
Purchase. Any notice of withdrawal must specify the name of the person who
tendered the Shares or Rights to be withdrawn, the number of Shares or Rights
to be withdrawn and the name of the registered holder, if different from that
of the person who tendered such Shares or Rights. If Share Certificates or
Rights Certificates to be withdrawn have been delivered or otherwise identified
to the Depositary, then, prior to the physical release of such certificates,
the serial numbers shown on such certificates must be submitted to the
Depositary and the signature(s) on the notice of withdrawal must be guaranteed
by an Eligible Institution (as defined in Section 3 of the Offer to Purchase)
unless such Shares or Rights have been tendered for the account of any Eligible
Institution. If Shares or Rights have been tendered pursuant to the procedure
for book-entry transfer as set forth in Section 3 of the Offer to Purchase, any
notice of withdrawal must specify the name and number of the account at the
Book-Entry Transfer Facility to be credited with the withdrawn Shares or Rights
and must otherwise comply with the procedures of such Book-Entry Transfer
Facility, in which case a notice of withdrawal will be effective if delivered
to the Depositary by any method of delivery described in the second sentence of
this paragraph. A withdrawal of Shares or Rights shall also constitute a
withdrawal of the associated Rights or Shares, as applicable. All questions as
to the form and validity (including time of receipt) of any notice of
withdrawal will be determined by the Purchaser, in its sole discretion, whose
determination will be final and binding. 

     The information required to be disclosed by Rule 14d-6(e)(1)(vii) of the
General Rules and Regulations under the Securities Exchange Act of 1934, as
amended (the "Exchange Act"), is contained in the Offer to Purchase and is
incorporated herein by reference.

     A request pursuant to Rule 14d-5 under the Exchange Act is being made to
the Company for the use of its shareholder list, list of the holders of Rights,
if any, and security position listings for the purpose of disseminating the
Offer to holders of Shares. Upon compliance by the Company with such request,
the Offer to Purchase and the related Letter of Transmittal and, if required,
other relevant materials will be mailed to record holders of Shares and Rights
whose names appear on the Company's shareholder list and list of holders of
Rights, if applicable, and will be furnished to brokers, dealers, commercial
banks, trust companies and similar persons whose names, or the names of whose
nominees, appear on the shareholder list and list of holders of Rights, if
applicable, or who are listed as participants in a clearing agency's security
position listing for subsequent transmittal to beneficial owners of Shares.

     THE OFFER TO PURCHASE AND THE RELATED LETTER OF TRANSMITTAL CONTAIN
IMPORTANT INFORMATION WHICH SHOULD BE READ BEFORE ANY DECISION IS MADE WITH
RESPECT TO THE 

<PAGE>
 
OFFER.

     Questions and requests for assistance may be directed to the Dealer Manager
or the Information Agent as set forth below. Requests for copies of the Offer
to Purchase and the related Letter of Transmittal and all other tender offer
materials may be directed to the Information Agent, and copies will be
furnished promptly at the Purchaser's expense. Shareholders may also contact
their broker, dealer, commercial bank or trust company for assistance
concerning the Offer. The Purchaser will not pay any fees or commissions to any
broker or dealer or any other person (other than the Dealer Manager and the
Information Agent) for soliciting tenders of Shares and Rights pursuant to the
Offer.

                    The Information Agent for the Offer is:

                             D.F. King & Co., Inc.

                                77 Water Street
                           New York, New York 10005
                         (212) 269-5550 (Call Collect)

                                      or

                          1-800-758-5378 (Toll Free)

                     The Dealer Manager for the Offer is:

                                Lehman Brothers

                           3 World Financial Center
                           New York, New York 10285
                       (212) 526-4089 or (212) 526-4758
                                (Call Collect)
October 25, 1994


<PAGE>
 
                 [LETTERHEAD OF THERMO ELECTRON APPEARS HERE]



                    THERMO ELECTRON ANNOUNCES TENDER OFFER
                              FOR PURITAN-BENNETT


WALTHAM, Mass., October 24, 1994--Thermo Electron Corporation (NYSE-TMO) 
announced today that it will commence, through a wholly owned subsidiary, a cash
tender offer at $24.50 per share for all of the outstanding shares of common 
stock of Puritan-Bennett Corporation (NASDAQ-PBEN) on October 25, 1994. The 
tender offer will expire at 12:00 midnight, Eastern Standard Time, on November 
22, 1994, unless extended by Thermo Electron.

     The closing of the tender offer is subject to a condition that the number 
of shares of Puritan-Bennett common stock tendered, together with the shares 
owned by Thermo Electron, constitute a majority of the Puritan-Bennett shares 
outstanding. The tender offer is also subject to certain conditions, including, 
but not limited to, the condition that Puritan-Bennett's shareholder rights 
plan, and certain anti-takeover provisions of Puritan-Bennett's articles of 
incorporation and Delaware law, be made inapplicable to the transaction. 
Satisfaction of one or more of these conditions will require approval, by the 
Puritan-Bennett board of directors, of the offer and the merger described in the
tender offer documents. The dealer manager for the offer is Lehman Brothers 
Inc., and the information agent is D.F. King & Co., Inc.

     Thermo Electron Corporation is a world leader in environmental monitoring 
and analysis instruments and a major manufacturer of biomedical products 
including heart-assist devices and mammography systems, papermaking and 
recycling equipment, alternative-energy systems, and other specialized products.
The company also provides environmental and metallurgical services and conducts 
advanced technology research and development. With annual worldwide sales of 
more than $1 billion, Thermo Electron has approximately 10,000 employees and 
operations in 14 countries. Headquarters are in Waltham, Massachusetts.

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