EXHIBIT 10.5


                            OPTION EXCHANGE AGREEMENT

             THIS AGREEMENT is made as of the 6th day of February, 1995,
        among Thermo Process Systems Inc., a Delaware Corporation
        ("Thermo"), and Emil C. Herkert, an individual whose primary
        residence is in the State of New Jersey ("Optionee").

             WHEREAS, pursuant to a Stock Purchase and Sale Agreement of
        even date herewith (the "Purchase and Sale Agreement"), Thermo
        has acquired 100% of the outstanding capital stock of Engineering
        Technology and Knowledge Corporation, a Delaware corporation
        ("ETKC");

             WHEREAS, ETKC owns 100% of the capital stock of Elson T.
        Killam Associates, Inc., a New Jersey corporation ("Killam");

             WHEREAS, Killam adopted an Incentive Stock Option Plan
        effective as of December 15, 1987 (the "Stock Option Plan");

             WHEREAS, the pursuant to a stock option agreement dated as
        of December 15, 1987, a copy of which is attached as Exhibit A
        hereto (the "Option Agreement"), Optionee owns a vested option
        (the "Killam Option") to purchase, in the aggregate, 365.52
        shares of the capital stock of Killam (after taking into account
        the cancellation of the Killam Option with respect to certain
        shares of the capital stock of Killam (the "Killam Stock"); and

             WHEREAS, Thermo wishes to acquire such Killam Option and to
        substitute therefor an economically equivalent option to purchase
        shares of Thermo's common stock, $.10 par value per share (the
        "Thermo Stock");
         
             NOW, THEREFORE, in consideration of the foregoing, of the
        mutual promises set forth herein and of the mutual promises set
        forth in the Purchase and Sale Agreement, and intending to be
        legally bound, the parties hereto hereby agree as follows:

             SECTION 1.  ASSUMPTION OF THE STOCK OPTION PLAN AND THE
        KILLAM OPTION.  Except as set forth below, Thermo hereby assumes
        and agrees to perform and discharge all liabilities, obligations
        and commitments of Killam which are set forth in the Stock Option
        Plan and the Option Agreement.  Thermo and Optionee hereby agree
        that the Killam Option is hereby converted, without any further
        action on the part of either party, into an option (the "Thermo
        Option") to purchase an aggregate of 250,000 shares of Thermo
        Stock.  Thermo and Optionee hereby agree that the exercise price
        of the Thermo Option shall be $.0824 per share of Thermo Stock.
        The assumption of the Stock Option Plan and the Killam Option and
        the conversion thereof of into the Thermo Option as provided
        herein shall not give Optionee additional benefits which he did
        not have immediately prior to the date hereof, result in any

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        acceleration of any vesting schedule for any Killam Option, or
        relieve Optionee of any obligation or restriction applicable to
        the Killam Option or the Killam Stock obtainable upon exercise of
        the Killam Option, including without limitation obligations and
        restrictions imposed by that certain Shareholders' Agreement
        dated January 29, 1995, as amended from time to time.  Thermo and
        Optionee agree that the foregoing assumption and conversion of
        the Killam Option is intended to comply with Internal Revenue
        Code Regulations governing incentive stock option roll-overs.  

             SECTION 2.  REPRESENTATIONS, WARRANTIES AND COVENANTS OF
        OPTIONEE.  Optionee represents and warrants to, and covenants
        with, Thermo that:  

             2.1.  OPTION AGREEMENT.  Attached hereto as Exhibit 1 is a
        true, correct and complete copy of Optionee's Option Agreement.
        The Option Agreement has not been amended, and is the sole
        instrument to which Optionee is a party that purports to grant
        Optionee any right to acquire shares of Killam Stock.  Optionee
        is the sole true, legal and beneficial owner of the Killam
        Option.  Optionee has not previously sold or transferred any
        interest in the Killam Option to any third party, has not
        pledged, mortgaged, hypothecated or otherwise encumbered the
        Killam Option or any or all of the Killam Stock.  No third party
        has been granted or has otherwise obtained, whether by operation
        of law or otherwise, any lien, security interest or other
        interest, contingent or otherwise, in or with respect to the
        Killam Option or in or with respect to any or all of the Killam
        Stock.

             2.2.  AUTHORITY.  The execution and delivery of this
        Agreement, and the consummation of the transactions contemplated
        hereby, have been duly and validly authorized by all necessary
        action on the part of Optionee.  This Agreement constitutes the
        valid and binding obligation of Optionee enforceable against him
        in accordance with the terms hereof, except as such
        enforceability may be limited by applicable bankruptcy,
        insolvency, reorganization, moratorium or other laws affecting
        the rights of creditors or by general principles of equity.
        Neither the execution, delivery and performance of this Agreement
        by Optionee, nor the consummation of the transactions
        contemplated hereby will (i) conflict with or result in a
        violation, breach, termination or acceleration of, or default
        under (or would result in such a violation, breach, termination,
        acceleration or default with the giving of notice or passage of
        time, or both) any of the terms, conditions or provisions of any
        note, bond, mortgage, indenture, agreement or other instrument or
        obligation to which Optionee is a party or by which Optionee or
        any of his properties or assets may be bound or affected; or (ii)
        result in the violation of any order, writ, injunction, decree,
        statute, rule or regulation applicable to Optionee or his
        properties or assets.
          
             2.3.  INVESTMENT REPRESENTATIONS.  

                                       -2-PAGE

                  (a)  Optionee has, in connection with his decision to
             acquire the Thermo Option, relied solely upon Thermo's
             Confidential Placement Memorandum dated January 29, 1995 and
             the documents incorporated therein by reference; and 

                  (b)  Taking into account the personnel and resources
             Optionee can practically bring to bear on the acquisition of
             the Thermo Options and the Thermo Stock contemplated hereby,
             Optionee is knowledgeable, sophisticated and experienced in
             making, and is able to make, decisions with respect to
             investments in securities presenting an investment decision
             like that involved in the acquisition of the Thermo Option
             and the Thermo Stock, including investments in securities
             issued by Thermo, and to assess the risks and merits
             presented by the acquisition of the Thermo Stock and the
             Thermo Options, and has requested, received, reviewed and
             considered all information he deems relevant in making an
             informed decision to acquire the Thermo Stock and the Thermo
             Options.

             SECTION 3.  REPRESENTATIONS, WARRANTIES AND COVENANTS OF
        THERMO.  Thermo hereby represents and warrants to, and covenants
        with, Optionee as follows:

             3.1.  ORGANIZATION AND QUALIFICATION.   Thermo is a
        corporation validly existing and in good standing under the laws
        of the State of Delaware, and has all requisite corporate power
        and authority to own, lease and operate its properties and to
        carry on its business as it is now being conducted.  

             3.2.  AUTHORITY.   The execution and delivery of this
        Agreement, and the consummation of the transactions contemplated
        hereby, have been duly and validly authorized by all necessary
        corporate action on the part of Thermo.  This Agreement
        constitutes the valid and binding obligation of Thermo
        enforceable against Thermo in accordance with the terms hereof,
        except as such enforceability may be limited by applicable
        bankruptcy, insolvency, reorganization, moratorium or other laws
        affecting the rights of creditors or by general principles of
        equity.  Neither the execution, delivery and performance of this
        Agreement by Thermo, nor the consummation of the transactions
        contemplated hereby will (i) conflict with or result in a
        violation, breach, termination or acceleration of, or default
        under (or would result in such a violation, breach, termination,
        acceleration or default with the giving of notice or passage of
        time, or both) any of the terms, conditions or provisions of the
        certificate of incorporation or bylaws of Thermo, each as
        amended, or of any note, bond, mortgage, indenture, agreement or
        other instrument or obligation to which Thermo is a party or by
        which Thermo or any of its properties or assets may be bound or
        affected; or (ii) result in the violation of any order, writ,
        injunction, decree, statute, rule or regulation applicable to
        Thermo or its properties or assets.  

                                       -3-PAGE

             3.3.   ASSUMPTION OF THE STOCK OPTION PLAN AND THE KILLAM
        OPTION; ISSUANCE, SALE AND DELIVERY OF THE THERMO STOCK.  The
        assumption of the Stock Option Plan and the Killam Option in
        accordance with the terms of this Agreement, and the conversion
        of the Killam Option into the Thermo Option, have been duly
        authorized under applicable law by all requisite corporate
        action.  The Thermo Stock (as set forth in Section 1) will be
        delivered to Optionee upon exercise of the Thermo Option, and
        upon payment by Optionee of the exercise price therefor, and as
        and when delivered, will be validly issued and outstanding, fully
        paid and nonassessable. 

             3.4.   ACCURACY OF INFORMATION.  The information contained
        in the Memorandum is true and correct in all material respects as
        of the date thereof.  

             SECTION 4.  NOTICES.  All notices, requests, demands,
        consents and other communications which are required or permitted
        hereunder shall be in writing, and shall be deemed given when
        actually received or if earlier, two days after deposit with the
        U.S. postal authorities, certified or registered mail, return
        receipt requested, postage prepaid or two days after deposit with
        an internationally recognized air courier or express mail,
        charges prepaid, addressed as follows:

             If to Thermo:

                  Thermo Process Systems Inc.
                  c/o Thermo Electron Corporation
                  81 Wyman Street
                  Waltham, Massachusetts  02254-9046
                  Attention:  President

             With a copy to:

                  Thermo Electron Corporation
                  81 Wyman Street
                  Waltham, Massachusetts  02254
                  Attention:  General Counsel

             If to Optionee:

                  Emil C. Herkert
                  c/o Killam Associates Inc.
                  27 Bleeker Street
                  P. O. Box 32
                  Millburn, New Jersey  07041-0032

             With a copy to:

                  Norris, McLaughlin & Marcus
                  721 Route 202-206
                  P. O. Box 1018

                                       -4-PAGE

                  Somerville, New Jersey  08876-1018
                  Attention: John J. Eagan, Esq.

        or to such other address as any party hereto may designate in
        writing to the other parties, specifying a change of address for
        the purpose of this Agreement.

             SECTION 5.  CHANGES.  This Agreement may not be modified or
        amended except pursuant to an instrument in writing signed by
        Thermo and Optionee.

             SECTION 6.  HEADINGS.  The headings of the various sections
        of this Agreement have been inserted for convenience of reference
        only and shall not be deemed to be part of this Agreement.

             SECTION 7.  SEVERABILITY.  In case any provision contained
        in this Agreement should be invalid, illegal or unenforceable in
        any respect, the validity, legality, and enforceability of the
        remaining provisions contained herein shall not in any way be
        affected or impaired thereby.

             SECTION 8.  GOVERNING LAW.  This Agreement shall be governed
        by and construed in accordance with the laws governing the Option
        Agreement.

             SECTION 9.  COUNTERPARTS.  This Agreement may be executed in
        counterparts, each of which shall constitute an original, but all
        of which, when taken together, shall constitute but one
        instrument, and shall become effective when one or more
        counterparts have been signed by each party hereto and delivered
        to the other parties.


             IN WITNESS WHEREOF, the parties hereto have caused this
        Agreement to be executed by their duly authorized representatives
        as of the day and year first above written.


        THERMO PROCESS SYSTEMS INC.        OPTIONEE


        By:  /s/ John P. Appleton          /s/ Emil C. Herkert

        Printed Name: John P. Appleton     Printed Name: Emil C. Herkert

        Title: President