content: <PAGE>
   
                       SECURITIES AND EXCHANGE COMMISSION
  
                             Washington, D.C. 20549
  
   
                                    FORM 8-K
  
                                 CURRENT REPORT
  
     Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934.
  
     Date of Report (Date of earliest event reported):    February 25, 1999
                                          
  
                                 THERMATRIX INC.
             (Exact name of Registrant as specified in its charter)
  
  
                         Commission File Number 0-20819
  
  
                Delaware                                   94-2958515
     (State or other jurisdiction of                    (I.R.S. Employer
      Incorporation or organization)                 Identification Number)
  
      2025 Gateway Place, Suite 132                        95110-1005
          San Jose, California                             (Zip Code)
  (Address of principal executive offices)
  
  
       Registrant's telephone number, including area code: (408) 453-0490
   
  <PAGE>
   
  ITEM 2.    ACQUISITION OR DISPOSITION OF ASSETS
  
       (a)   On January 13, 1999, Thermatrix Inc., a Delaware corporation
  ("Thermatrix") acquired Wahlco Environmental Systems, Inc., a Delaware
  corporation ("Wahlco") in a transaction whereby Wahlco was merged with and into
  a wholly-owned subsidiary of Thermatrix (the "Merger"). In connection with the
  Merger, Thermatrix agreed (i) to guaranty obligations (the "Thermatrix
  Guaranty") of Wahlco arising from a non-committed line of credit with The Chase
  Manhattan Bank (the "Chase Notes," which were subsequently purchased from The
  Chase Manhattan Bank by Wexford and the Lenders on January 22, 1999), and a
  Credit Agreement (the "1998 Credit Agreement") among Wahlco, Wexford Management
  LLC ("Wexford") and several lenders affiliated with Wexford (the "Lenders"), and
  (ii) to secure such obligations by granting a security interest in all existing
  and future assets of Thermatrix (the "Original Security Agreement").
  
       On February 25, 1999, Thermatrix, Wahlco, the Lenders and Wexford entered
  into a Second Amended and Restated Credit Agreement (the "1999 Credit
  Agreement") which amends and restates the 1998 Credit Agreement, the Thermatrix
  Guaranty and the Chase Notes, and pursuant to which: (i) Thermatrix became a co-
  obligor; (ii) the outstanding obligations (which include the obligations arising
  under the Chase Notes and the Thermatrix Guaranty) are approximately $5.72
  million and bear interest at a rate of 13% per annum payable monthly, with no
  commitment by Wexford and the Lenders to advance any additional loans or
  extensions of credit to Thermatrix or Wahlco; (iii) the outstanding principal
  amount of the obligations will become due and payable six months from the date
  thereof, provided that such due date may be extended an additional ninety days
  for a fee of one hundred thousand dollars ($100,000); (iv) the Original Security
  Agreement was amended and restated to confirm the security interest granted to
  Wexford and the Lenders in Thermatrix's existing and future assets; (v)
  Thermatrix issued to Wexford a net exercise Warrant exercisable for up to four
  hundred fifty thousand (450,000) shares of Thermatrix Common Stock, with certain
  registration rights thereon; (vi) Thermatrix's significant direct and indirect
  subsidiaries in the U.S. and the U.K. guaranteed the obligations arising under
  the 1999 Credit Agreement and secured such obligations by granting a security
  interest in all of such subsidiaries' existing and future assets (including real
  property owned by such subsidiaries); (vii) Thermatrix and Wahlco delivered a
  General Release in favor of Wexford and certain other parties related to
  Wexford.
  
  <PAGE>
   
  ITEM 7       FINANCIAL STATEMENTS AND EXHIBITS.
  
        The following exhibits are filed as part of this Report, in accordance
  with item 601 of Regulations S-K, where indicated.
  
  Exhibit
  Number    Description
  ------    -----------
  
     10.1   Second Amended and Restated Credit Agreement dated February 25, 1999
            by and among Wahlco Environmental Systems, Inc., Thermatrix Inc.,
            Wexford Capital Partners II, L.P., Wexford Overseas Partners I,
            L.P., Wexford Special Situations 1996, L.P., Wexford Special
            Situations 1996 Institutional, L.P., Wexford Special Situations 1996
            Limited, Wexford-Euris Special Situations 1996, L.P. and Wexford
            Management LLC, as Agent
  
     10.2   General Release dated February 25, 1999 by and among Wahlco
            Environmental Systems, Inc., Thermatrix Inc., Wexford Capital Partners
            II, L.P., Wexford Overseas Partners I, L.P., Wexford Special
            Situations 1996, L.P., Wexford Special Situations 1996 Institutional,
            L.P., Wexford Special Situations 1996 Limited, Wexford-Euris Special
            Situations 1996, L.P. and Wexford Management LLC, as Agent
  
     10.3   Amended and Restated Guaranty dated February 25, 1999 by and among
            Bachmann Companies, Inc., Wahlco Engineered Products Group, LTD.,
            Wahlco, Inc., WES Property, LTD., Wahlco Engineered Products, Inc.,
            Wahlco Engineered Products, Ltd., Pentney Engineering, LTD.,
            Teddington Bellows (Holdings), LTD., Teddington Bellows, Ltd., Treste
            Plant Hire, LTD., Thermatrix, LTD. and Wexford Management LLC, as
            Agent
  
     10.4   Mortgage, Security Agreement Assignment of Rents and Leases and
            Fixture Filing dated February 25, 1999 by and between Wahlco 
            Engineered Products, Inc. and Wexford Management LLC, as Agent
  
     10.5   Mortgage, Security Agreement Assignment of Rents and Leases and
            Fixture Filing dated February 25, 1999 by and between Wahlco, Inc. and
            Wexford Management LLC, as Agent
  
     10.6   Promissory Note dated February 25, 1999 in the principal amount of
            $5,720,585.64, delivered by Thermatrix Inc. and Wahlco Environmental
            Systems, Inc. to Wexford Management LLC, as Agent
            
     10.7   Registration Rights Agreement dated February 25, 1999 by and between
            Thermatrix Inc. and Wexford Management LLC 
  
     10.8   Amended and Restated Security Agreement dated February 25, 1999 by and
            among Wahlco Environmental Systems, Inc., Bachmann Companies, Inc., 
            Wahlco, Inc., Wahlco Engineered Products, Inc. and Wexford Management 
            LLC, as Agent
  
     10.9   Amended and Restated Security Agreement dated February 25, 1999 by and
            between Thermatrix Inc., Wexford Capital Partners II, L.P., Wexford
            Overseas Partners I, L.P., Wexford Special Situations 1996
            Institutional, L.P., Wexford Special Situations 1996 Limited, Wexford-
            Euris Special Situations 1996, L.P. and Wexford Management LLC, as
            Agent
  
     10.10  Form of U.K. Debenture entered into by and between Wexford Management 
            LLC and each of Pentney Engineering Limited, Teddington Bellows
            (Holdings) LTD., Teddington Bellows Ltd., Thermatrix, LTD., Treste
            Plant Hire, LTD., WES Property, LTD., Wahlco Engineered Products
            Group, LTD. and Wahlco Engineered Products LTD., respectively
  
     10.11  Stock Pledge Agreement dated February 25, 1999 by and among 
            Thermatrix Inc., Wahlco Environmental Systems, Inc., Bachmann
            Companies, Inc., Wahlco Engineered Products Group LTD., Wahlco
            Engineered Products LTD., Teddington Bellows (Holdings), LTD. and
            Wexford Management LLC, as Agent
  
     10.12  Warrant to purchase up to 450,000 shares of Common Stock of Thermatrix
            Inc. issued to Wexford Management LLC on February 25, 1999
  
  
  <PAGE>
   
                                   SIGNATURES
  
            Pursuant to the requirements of the Securities Exchange Act of 1934,
  the registrant has duly caused this report to be signed on its behalf by the
  undersigned hereunto duly authorized.
  
  
  
                                      THERMATRIX INC.
  
  
  
  Date: March 11, 1999                By: /s/ Daniel S. Tedone             
                                          ------------------------------
                                          Daniel S. Tedone
                                          Chief Financial Officer
  <PAGE>
   
                                  EXHIBIT INDEX
  
  
  Exhibit
   Number     Description
  -------     -----------
  
    10.1      Second Amended and Restated Credit Agreement dated February 25, 1999
              by and among Wahlco Environmental Systems, Inc., Thermatrix Inc.,
              Wexford Capital Partners II, L.P., Wexford Overseas Partners I,
              L.P., Wexford Special Situations 1996, L.P., Wexford Special
              Situations 1996 Institutional, L.P., Wexford Special Situations 1996
              Limited, Wexford-Euris Special Situations 1996, L.P. and Wexford
              Management LLC, as Agent
  
    10.2      General Release dated February 25, 1999 by and among Wahlco 
              Environmental Systems, Inc., Thermatrix Inc., Wexford Capital
              Partners II, L.P., Wexford Overseas Partners I, L.P., Wexford
              Special Situations 1996, L.P., Wexford Special Situations 1996
              Institutional, L.P., Wexford Special Situations 1996 Limited,
              Wexford-Euris Special Situations 1996, L.P. and Wexford Management
              LLC, as Agent
  
    10.3      Amended and Restated Guaranty dated February 25, 1999 by and among 
              Bachmann Companies, Inc., Wahlco Engineered Products Group, LTD.,
              Wahlco, Inc., WES Property, LTD., Wahlco Engineered Products, Inc.,
              Wahlco Engineered Products, Ltd., Pentney Engineering, LTD.,
              Teddington Bellows (Holdings), LTD., Teddington Bellows Ltd., Treste
              Plant Hire, LTD., Thermatrix, LTD. and Wexford Management LLC, as 
              Agent
  
    10.4      Mortgage, Security Agreement Assignment of Rents and Leases and
              Fixture Filing dated February 25, 1999 by and between Wahlco
              Engineered Products, Inc. and Wexford Management LLC, as agent
  
    10.5      Mortgage, Security Agreement Assignment of Rents and Leases and 
              Fixture Filing dated February 25, 1999 by and between Wahlco, Inc.
              and Wexford Management LLC, as Agent
  
    10.6      Promissory Note dated February 25, 1999 in the principal amount of
              $5,720,585.64, delivered by Thermatrix Inc. and Wahlco Environmental
              Systems, Inc. to Wexford Management LLC, as Agent
  
    10.7      Registration Rights Agreement dated February 25, 1999 by and between
              Thermatrix Inc. and Wexford Management LLC
  
    10.8      Amended and Restated Security Agreement dated February 25, 1999 by
              and among Wahlco Environmental Systems, Inc., Bachmann Companies, 
              Inc., Wahlco, Inc., Wahlco Engineered Products, Inc. and Wexford 
              Management LLC, as agent
  
    10.9      Amended and Restated Security Agreement dated February 25, 1999 by
              and between Thermatrix Inc., Wexford Capital Partners II, L.P.,
              Wexford Overseas Partners I, L.P., Wexford Special Situations 1996
              Institutional, L.P., Wexford Special Situations 1996 Limited, 
              Wexford-Euris Special Situations 1996, L.P. and Wexford Management
              LLC, as Agent
  
    10.10     Form of U.K. Debenture entered into by and between Wexford
              Management LLC and each of Pentney Engineering Limited, Teddington
              Bellow (Holdings) LTD., Teddington Bellows Ltd., Thermatrix, LTD.
              Treste Plant Hire, LTD., WES Property, LTD., Wahlco Engineered
              Products Group, LTD. and Wahlco Engineered Products LTD.,
              respectively
  
    10.11     Stock Pledge Agreement dated February 25, 1999 by and among 
              Thermatrix Inc., Wahlco Environmental Systems, Inc., Bachmann
              Companies, Inc., Wahlco Engineered Products Group LTD., Teddington
              Bellows (Holdings), Ltd. and Wexford Management LLC, as Agent
  
    10.12     Warrant to purchase up to 450,000 shares of Common Stock of 
              Thermatrix Inc. issued to Wexford Management LLC on February 25, 
              1999
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text: SECURITIES AND EXCHANGE COMMISSION
  
                             Washington, D.C. 20549
  
   
                                    FORM 8-K
  
                                 CURRENT REPORT
  
     Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934.
  
     Date of Report (Date of earliest event reported):    February 25, 1999
                                          
  
                                 THERMATRIX INC.
             (Exact name of Registrant as specified in its charter)
  
                         Commission File Number 0-20819
  
                Delaware                                   94-2958515
     (State or other jurisdiction of                    (I.R.S. Employer
      Incorporation or organization)                 Identification Number)
  
      2025 Gateway Place, Suite 132                        95110-1005
          San Jose, California                             (Zip Code)
  (Address of principal executive offices)
  
       Registrant's telephone number, including area code: (408) 453-0490
  ITEM 2.    ACQUISITION OR DISPOSITION OF ASSETS
  
       (a)   On January 13, 1999, Thermatrix Inc., a Delaware corporation
  ("Thermatrix") acquired Wahlco Environmental Systems, Inc., a Delaware
  corporation ("Wahlco") in a transaction whereby Wahlco was merged with and into
  a wholly-owned subsidiary of Thermatrix (the "Merger"). In connection with the
  Merger, Thermatrix agreed (i) to guaranty obligations (the "Thermatrix
  Guaranty") of Wahlco arising from a non-committed line of credit with The Chase
  Manhattan Bank (the "Chase Notes," which were subsequently purchased from The
  Chase Manhattan Bank by Wexford and the Lenders on January 22, 1999), and a
  Credit Agreement (the "1998 Credit Agreement") among Wahlco, Wexford Management
  LLC ("Wexford") and several lenders affiliated with Wexford (the "Lenders"), and
  (ii) to secure such obligations by granting a security interest in all existing
  and future assets of Thermatrix (the "Original Security Agreement").
  
       On February 25, 1999, Thermatrix, Wahlco, the Lenders and Wexford entered
  into a Second Amended and Restated Credit Agreement (the "1999 Credit
  Agreement") which amends and restates the 1998 Credit Agreement, the Thermatrix
  Guaranty and the Chase Notes, and pursuant to which: (i) Thermatrix became a co-
  obligor; (ii) the outstanding obligations (which include the obligations arising
  under the Chase Notes and the Thermatrix Guaranty) are approximately $5.72
  million and bear interest at a rate of 13% per annum payable monthly, with no
  commitment by Wexford and the Lenders to advance any additional loans or
  extensions of credit to Thermatrix or Wahlco; (iii) the outstanding principal
  amount of the obligations will become due and payable six months from the date
  thereof, provided that such due date may be extended an additional ninety days
  for a fee of one hundred thousand dollars ($100,000); (iv) the Original Security
  Agreement was amended and restated to confirm the security interest granted to
  Wexford and the Lenders in Thermatrix's existing and future assets; (v)
  Thermatrix issued to Wexford a net exercise Warrant exercisable for up to four
  hundred fifty thousand (450,000) shares of Thermatrix Common Stock, with certain
  registration rights thereon; (vi) Thermatrix's significant direct and indirect
  subsidiaries in the U.S. and the U.K. guaranteed the obligations arising under
  the 1999 Credit Agreement and secured such obligations by granting a security
  interest in all of such subsidiaries' existing and future assets (including real
  property owned by such subsidiaries); (vii) Thermatrix and Wahlco delivered a
  General Release in favor of Wexford and certain other parties related to
  Wexford.
  ITEM 7       FINANCIAL STATEMENTS AND EXHIBITS.
  
        The following exhibits are filed as part of this Report, in accordance
  with item 601 of Regulations S-K, where indicated.
  
  Exhibit
  Number    Description
  ------    -----------
  
     10.1   Second Amended and Restated Credit Agreement dated February 25, 1999
            by and among Wahlco Environmental Systems, Inc., Thermatrix Inc.,
            Wexford Capital Partners II, L.P., Wexford Overseas Partners I,
            L.P., Wexford Special Situations 1996, L.P., Wexford Special
            Situations 1996 Institutional, L.P., Wexford Special Situations 1996
            Limited, Wexford-Euris Special Situations 1996, L.P. and Wexford
            Management LLC, as Agent
  
     10.2   General Release dated February 25, 1999 by and among Wahlco
            Environmental Systems, Inc., Thermatrix Inc., Wexford Capital Partners
            II, L.P., Wexford Overseas Partners I, L.P., Wexford Special
            Situations 1996, L.P., Wexford Special Situations 1996 Institutional,
            L.P., Wexford Special Situations 1996 Limited, Wexford-Euris Special
            Situations 1996, L.P. and Wexford Management LLC, as Agent
  
     10.3   Amended and Restated Guaranty dated February 25, 1999 by and among
            Bachmann Companies, Inc., Wahlco Engineered Products Group, LTD.,
            Wahlco, Inc., WES Property, LTD., Wahlco Engineered Products, Inc.,
            Wahlco Engineered Products, Ltd., Pentney Engineering, LTD.,
            Teddington Bellows (Holdings), LTD., Teddington Bellows, Ltd., Treste
            Plant Hire, LTD., Thermatrix, LTD. and Wexford Management LLC, as
            Agent
  
     10.4   Mortgage, Security Agreement Assignment of Rents and Leases and
            Fixture Filing dated February 25, 1999 by and between Wahlco 
            Engineered Products, Inc. and Wexford Management LLC, as Agent
  
     10.5   Mortgage, Security Agreement Assignment of Rents and Leases and
            Fixture Filing dated February 25, 1999 by and between Wahlco, Inc. and
            Wexford Management LLC, as Agent
  
     10.6   Promissory Note dated February 25, 1999 in the principal amount of
            $5,720,585.64, delivered by Thermatrix Inc. and Wahlco Environmental
            Systems, Inc. to Wexford Management LLC, as Agent
            
     10.7   Registration Rights Agreement dated February 25, 1999 by and between
            Thermatrix Inc. and Wexford Management LLC 
  
     10.8   Amended and Restated Security Agreement dated February 25, 1999 by and
            among Wahlco Environmental Systems, Inc., Bachmann Companies, Inc., 
            Wahlco, Inc., Wahlco Engineered Products, Inc. and Wexford Management 
            LLC, as Agent
  
     10.9   Amended and Restated Security Agreement dated February 25, 1999 by and
            between Thermatrix Inc., Wexford Capital Partners II, L.P., Wexford
            Overseas Partners I, L.P., Wexford Special Situations 1996
            Institutional, L.P., Wexford Special Situations 1996 Limited, Wexford-
            Euris Special Situations 1996, L.P. and Wexford Management LLC, as
            Agent
  
     10.10  Form of U.K. Debenture entered into by and between Wexford Management 
            LLC and each of Pentney Engineering Limited, Teddington Bellows
            (Holdings) LTD., Teddington Bellows Ltd., Thermatrix, LTD., Treste
            Plant Hire, LTD., WES Property, LTD., Wahlco Engineered Products
            Group, LTD. and Wahlco Engineered Products LTD., respectively
  
     10.11  Stock Pledge Agreement dated February 25, 1999 by and among 
            Thermatrix Inc., Wahlco Environmental Systems, Inc., Bachmann
            Companies, Inc., Wahlco Engineered Products Group LTD., Wahlco
            Engineered Products LTD., Teddington Bellows (Holdings), LTD. and
            Wexford Management LLC, as Agent
  
     10.12  Warrant to purchase up to 450,000 shares of Common Stock of Thermatrix
            Inc. issued to Wexford Management LLC on February 25, 1999
  SIGNATURES
  
            Pursuant to the requirements of the Securities Exchange Act of 1934,
  the registrant has duly caused this report to be signed on its behalf by the
  undersigned hereunto duly authorized.
  
                                      THERMATRIX INC.
  
  Date: March 11, 1999                By: /s/ Daniel S. Tedone             
                                          ------------------------------
                                          Daniel S. Tedone
                                          Chief Financial Officer
  EXHIBIT INDEX
  
  Exhibit
   Number     Description
  -------     -----------
  
    10.1      Second Amended and Restated Credit Agreement dated February 25, 1999
              by and among Wahlco Environmental Systems, Inc., Thermatrix Inc.,
              Wexford Capital Partners II, L.P., Wexford Overseas Partners I,
              L.P., Wexford Special Situations 1996, L.P., Wexford Special
              Situations 1996 Institutional, L.P., Wexford Special Situations 1996
              Limited, Wexford-Euris Special Situations 1996, L.P. and Wexford
              Management LLC, as Agent
  
    10.2      General Release dated February 25, 1999 by and among Wahlco 
              Environmental Systems, Inc., Thermatrix Inc., Wexford Capital
              Partners II, L.P., Wexford Overseas Partners I, L.P., Wexford
              Special Situations 1996, L.P., Wexford Special Situations 1996
              Institutional, L.P., Wexford Special Situations 1996 Limited,
              Wexford-Euris Special Situations 1996, L.P. and Wexford Management
              LLC, as Agent
  
    10.3      Amended and Restated Guaranty dated February 25, 1999 by and among 
              Bachmann Companies, Inc., Wahlco Engineered Products Group, LTD.,
              Wahlco, Inc., WES Property, LTD., Wahlco Engineered Products, Inc.,
              Wahlco Engineered Products, Ltd., Pentney Engineering, LTD.,
              Teddington Bellows (Holdings), LTD., Teddington Bellows Ltd., Treste
              Plant Hire, LTD., Thermatrix, LTD. and Wexford Management LLC, as 
              Agent
  
    10.4      Mortgage, Security Agreement Assignment of Rents and Leases and
              Fixture Filing dated February 25, 1999 by and between Wahlco
              Engineered Products, Inc. and Wexford Management LLC, as agent
  
    10.5      Mortgage, Security Agreement Assignment of Rents and Leases and 
              Fixture Filing dated February 25, 1999 by and between Wahlco, Inc.
              and Wexford Management LLC, as Agent
  
    10.6      Promissory Note dated February 25, 1999 in the principal amount of
              $5,720,585.64, delivered by Thermatrix Inc. and Wahlco Environmental
              Systems, Inc. to Wexford Management LLC, as Agent
  
    10.7      Registration Rights Agreement dated February 25, 1999 by and between
              Thermatrix Inc. and Wexford Management LLC
  
    10.8      Amended and Restated Security Agreement dated February 25, 1999 by
              and among Wahlco Environmental Systems, Inc., Bachmann Companies, 
              Inc., Wahlco, Inc., Wahlco Engineered Products, Inc. and Wexford 
              Management LLC, as agent
  
    10.9      Amended and Restated Security Agreement dated February 25, 1999 by
              and between Thermatrix Inc., Wexford Capital Partners II, L.P.,
              Wexford Overseas Partners I, L.P., Wexford Special Situations 1996
              Institutional, L.P., Wexford Special Situations 1996 Limited, 
              Wexford-Euris Special Situations 1996, L.P. and Wexford Management
              LLC, as Agent
  
    10.10     Form of U.K. Debenture entered into by and between Wexford
              Management LLC and each of Pentney Engineering Limited, Teddington
              Bellow (Holdings) LTD., Teddington Bellows Ltd., Thermatrix, LTD.
              Treste Plant Hire, LTD., WES Property, LTD., Wahlco Engineered
              Products Group, LTD. and Wahlco Engineered Products LTD.,
              respectively
  
    10.11     Stock Pledge Agreement dated February 25, 1999 by and among 
              Thermatrix Inc., Wahlco Environmental Systems, Inc., Bachmann
              Companies, Inc., Wahlco Engineered Products Group LTD., Teddington
              Bellows (Holdings), Ltd. and Wexford Management LLC, as Agent
  
    10.12     Warrant to purchase up to 450,000 shares of Common Stock of 
              Thermatrix Inc. issued to Wexford Management LLC on February 25, 
              1999