<PAGE>
 
AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON SEPTEMBER 19, 1996
                                                   REGISTRATION NO. 333-
=============================================================================== 

 
                      SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C. 20549

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

                                   FORM S-8
                            REGISTRATION STATEMENT
                                     UNDER
                          THE SECURITIES ACT OF 1933

                         ----------------------------
 
                                THERMATRIX INC.
              (EXACT NAME OF ISSUER AS SPECIFIED IN ITS CHARTER)
 
                         ---------------------------

       DELAWARE                                         94-2958515
  ------------------                                    ----------
(STATE OF INCORPORATION)                   (I.R.S. EMPLOYER IDENTIFICATION NO.)
 
                          101 METRO DRIVE, SUITE 248
                          SAN JOSE, CALIFORNIA 95110
                   (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)
 
                   ----------------------------------------

                           1987 INCENTIVE STOCK PLAN
                                1996 STOCK PLAN
                         EMPLOYEE STOCK PURCHASE PLAN
                           1996 DIRECTOR OPTION PLAN
                           (FULL TITLE OF THE PLAN)

                   ----------------------------------------
 
                               JOHN T. SCHOFIELD
                CHAIRMAN, PRESIDENT AND CHIEF EXECUTIVE OFFICER
                                THERMATRIX INC.
                          101 METRO DRIVE, SUITE 248
                          SAN JOSE, CALIFORNIA 95110
                                (408) 453-0490
(NAME, ADDRESS, AND TELEPHONE NUMBER, INCLUDING AREA CODE, OF AGENT FOR SERVICE)

                   -----------------------------------------
 
                                   Copy to:
                           ALISANDE M. ROZYNKO, ESQ.
                       WILSON SONSINI GOODRICH & ROSATI
                           PROFESSIONAL CORPORATION
                              650 PAGE MILL ROAD
                           PALO ALTO, CA 94304-1050
                                (415) 493-9300
 

================================================================================
<PAGE>
 
<TABLE>
<CAPTION>
                             CALCULATION OF REGISTRATION FEE
=========================================================================================
 
      Title of             Maximum            Proposed       Proposed       Amount of
     Securities             Amount            Maximum         Maximum      Registration
       to be                to be             Offering       Aggregate         Fee
     Registered            Registered         Price Per       Offering
                                                Share           Price
- ----------------------------------------------------------------------------------------
<S>                    <C>                    <C>            <C>             <C>
Common Stock,                                       
  $.001 par value...   746,997  shares(1)     $1.61 (2)     $1,202,665.17(2)    $  414.71
Common Stock,                                                       
  $.001 par value...   333,334  shares(3)     $8.25 (4)     $2,750,005.50       $  948.28
Common Stock,                                                       
  $.001 par value...   116,667  shares(5)     $8.25 (6)     $  818,127.34       $  282.11
Common Stock,                                        
  $.001 par value...    83,334  shares(7)     $8.25 (8)     $  857,514.00       $  295.69
          TOTAL        1,280,332  SHARES         --         $5,628,312.01       $1,940.80
=========================================================================================
</TABLE>
(1)   For the sole purpose of calculating the registration fee, the number of
      shares to be registered under this Registration Statement has been broken
      down into four subtotals.  This subtotal represents the sum of shares
      issuable upon exercise of presently outstanding options (options that have
      been granted as of the date of this Registration Statement) issued under
      the 1987 Stock Plan.

(2)   Computed in accordance with Rule 457(h) under the Securities Act of 1933
      solely for the purpose of calculating the total registration fee.  This
      computation is based on the weighted average exercise price (rounded to
      nearest cent) at which the options outstanding whose exercise will result
      in the issuance of the shares being registered may be exercised.

(3)   This sub-total represents the sum of shares authorized to be issued under
      the 1996 Stock Plan.

(4)   Estimated in accordance with Rule 457(h) under the Securities Act of 1933
      solely for the purpose of calculating the total registration fee.  This
      computation is based upon the average of the high and low prices of the
      Common Stock as reported in The Nasdaq National Market on September 18,
      1996.

(5)   This sub-total represents the number of shares authorized to be issued
      under the Employee Stock Purchase Plan.

(6)   Estimated in accordance with Rule 457(h) under the Securities Act of 1933
      solely for the purpose of calculating the total registration fee.
      Computation based upon 85% (see explanation in following sentence) of the
      average of the high and low prices of the Common Stock as reported in The
      Nasdaq National Market on September 18, 1996.  Pursuant to the Employee
      Stock Purchase Plan, which plan is incorporated by reference herein, the
      purchase price of a share of Common Stock shall be an amount equal to 85%
      of the Fair Market Value of a share of Common Stock on the Enrollment Date
      or the Exercise Date (as defined in such Plan), whichever is lower.

(7)   This sub-total represents the number of shares authorized to be issued
      under the 1996 Director Option Plan  This sub-total includes 40,002 shares
      that were granted to the Directors on June 19, 1996 with a  exercise price
      of $12.50.  43,332 shares are available for issuance under the Director
      Option Plan.

(8)   Options were granted on June 19, 1996 to the Directors with a exercise
      price of $12.50.  Future Director option grants computation is based upon
      the average of the high and low prices of the Common Stock as reported in
      the Nasdaq National Market on September 18, 1996 because the price at
      which the options to be granted in the future may be exercised is not
      currently determinable.

                                     -ii-
<PAGE>
 
                                THERMATRIX INC.
                      REGISTRATION STATEMENT ON FORM S-8

                                    PART II

                INFORMATION REQUIRED IN REGISTRATION STATEMENT
                                        
ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE
         ---------------------------------------

         There are hereby incorporated by reference in this Registration
Statement the following documents and information heretofore filed by Thermatrix
Inc. (the "Company") with the Securities and Exchange Commission:

         (1)  The Company's Registration Statement on Form S-1 (file no. 333-
4370) filed under the Securities Act of 1933, as amended (the "Securities Act"),
in the form declared effective on June 19, 1996.

         (2)  The description of the Company's Common Stock contained in the
Company's Registration Statement on Form 8-A filed May 1, 1996 pursuant to
Section 12(g) of the Securities Exchange Act of 1934, as amended (the "Exchange
Act") and declared effective on June 19, 1996.

         (3)  The Form 10-Q of the Registrant filed pursuant to Section 31(a) of
the Securities Exchange Act of 1934 (the "Exchange Act") on August 14, 1996.

         (4)  All documents filed by the Company pursuant to Sections 13(a),
13(c), 14 and 15(d) of the Exchange Act on or after the date of this
Registration Statement and prior to the filing of a post-effective amendment
which indicates that all securities offered have been sold or which deregisters
all securities then remaining unsold shall be deemed to be incorporated by
reference in this Registration Statement and to be part hereof from the date of
filing of such documents.

ITEM 4.  DESCRIPTION OF SECURITIES.
         ------------------------- 

         Not applicable.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.
         -------------------------------------- 

         As of the date hereof, certain members of Wilson, Sonsini, Goodrich &
Rosati, Professional Corporation beneficially owned a total of 8,940 shares of
the registrants Common Stock. Mario M. Rosati, the Assistant Secretary of the
Company, is a member of Wilson Sonsini Goodrich & Rosati.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.
         ----------------------------------------- 

         Section 145(a) of the Delaware General Corporation Law (the "DGCL")
provides in relevant part that "a corporation shall have power to indemnify any
person who was or is a party or is threatened to be made a party to any
threatened, pending or completed action, suit or proceeding, whether civil,
criminal, administrative or investigative (other than an action by or in the
right of the corporation) by reason of the fact that he is or was a director,
officer, employee or agent of the corporation, partnership, joint venture, trust
or other enterprise, against expenses (including attorneys' fees), judgments,
fines and amounts paid in settlement actually and reasonably incurred by him in
connection with such action, suit or proceeding if he acted in good faith and in
a manner he reasonably believed to be in or not opposed to the best interests of
the corporation, and, with respect to any criminal action or proceeding,

<PAGE>

had no reasonable cause to believe his conduct was unlawful." With respect to
derivative actions, Section 145(b) of the DGCL provides in relevant part that
"[a] corporation shall have power to indemnify any person who was or is a party
or is threatened to be made a party to any threatened, pending or completed
action or suit by or in the right of the corporation to procure a judgment in
its favor . . . [by reason of his service in one of the capacities specified in
the preceding sentence] against expenses (including attorneys' fees) actually
and reasonably incurred by him in connection with the defense or settlement of
such action or suit if he acted in good faith and in a manner he reasonably
believed to be in or not opposed to the best interests of the corporation and
except that no indemnification shall be made in respect of any claim, issue or
matter as to which such person shall have been adjudged to be liable to the
corporation unless and only to the extent that the Court of Chancery or the
court in which such action or suit was brought shall determine upon application
that, despite the adjudication of liability but in view of all the circumstances
of the case, such person is fairly and reasonably entitled to indemnity for such
expenses which the Court of Chancery or such other court shall deem proper."

         The Company's Restated Certificate of Incorporation provides that to
the fullest extent permitted by the DGCL, no director of the Company shall be
personally liable to the Company or its stockholders for monetary damages for
breach of fiduciary duty as a director. The Certificate of Incorporation also
provides that no amendment or repeal of such provision shall apply to or have
any effect on the right to indemnification permitted thereunder with respect to
claims arising from acts or omissions occurring in whole or in part before the
effective date of such amendment or repeal whether asserted before or after such
amendment or repeal.

         The Company's Bylaws provide that the Company shall indemnify to the
full extent authorized by law each of its directors, officers, employees and
other agents against expenses actually and reasonably incurred in connection
with any proceeding arising by reason of the fact that such person is or was an
agent of the corporation.

         The Company has entered into indemnification agreements with its
directors and executive officers, in addition to indemnification provided for in
the Company's Bylaws, and intends to enter into indemnification agreements with
any new directors and executive officers in the future.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED.
         ----------------------------------- 

         Not applicable
 
ITEM 8.  EXHIBITS.
         -------- 
<TABLE>
<CAPTION>
 
    Exhibit                             Description
    Number
    -------     ----------------------------------------------------------------
    <C>         <S>
      4.1*      Specimen Stock Certificate

      4.2*      Amended and Restated Investor Rights Agreement

      5.1       Opinion of counsel as to legality of securities being registered.

     10.2A*     1987 Incentive Stock Plan and form of Stock Option Agreement
                thereunder.

     10.3A*     1996 Stock Plan and form of Stock Option Agreement thereunder.

     10.4A*     Employee Stock Purchase Plan and forms of agreements thereunder.

     10.5*      1996 Director Option Plan and form of Director Stock Option
                Agreement thereunder.

     23.1       Consent of counsel (contained in Exhibit 5.1).

</TABLE> 

                                      II-2
<PAGE>
 
<TABLE>
<CAPTION>
 
    Exhibit                             Description
    Number
    -------     ----------------------------------------------------------------
    <C>         <S>
     23.2       Consent of Arthur Andersen LLP
     24.1       Power of Attorney (see page II-4).
</TABLE> 
- ---------------
*     Incorporated by reference to exhibits filed with the Company's
      Registration Statement on Form S-1 (file no. 333-4370), in the form
      declared effective on June 19, 1996.

ITEM 9.  UNDERTAKINGS.
         ------------ 

    A.   The Company hereby undertakes:

         (1)  To file, during any period in which offers or sales are being
made, a post-effective amendment to this registration statement to include any
material information with respect to the plan of distribution not previously
disclosed in the registration statement or any material change to such
information in the registration statement.

         (2)  That, for the purpose of determining any liability under the
Securities Act, each such post-effective amendment shall be deemed to be a new
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

         (3)  To remove from registration by means of a post-effective amendment
any of the securities being registered which remain unsold at the termination of
the offering.

    B.   Insofar as indemnification for liabilities arising under the Securities
Act may be permitted to directors, officers and controlling persons of the
Company pursuant to the Corporation Law, the Company's Certificate of
Incorporation, the Company's Bylaws or the Company's indemnification agreements,
the Company has been advised that in the opinion of the Securities and Exchange
Commission such indemnification is against public policy as expressed in the
Securities Act and is therefore unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the Company
of expenses incurred or paid by a director, officer or controlling person of the
Company in the successful defense of any action, suit or proceeding) is asserted
by such director, officer or controlling person in connection with the
securities being registered hereunder, the Company will, unless in the opinion
of its counsel the question has already been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question of whether such
indemnification by it is against public policy as expressed in the Securities
Act and will be governed by the final adjudication of such issue.

                                      II-3
<PAGE>
 
                                  SIGNATURES

       Pursuant to the requirements of the Securities Act of 1933, the
Registrant, Thermatrix Inc., a corporation organized and existing under the laws
of the State of Delaware, certifies that it has reasonable grounds to believe
that it meets all of the requirements for filing on Form S-8 and has duly caused
this registration statement to be signed on its behalf by the undersigned,
thereunto duly authorized, in the City of San Jose, State of California, on this
19th day of September, 1996.

                                    THERMATRIX INC.

                                    By:  /s/ John T. Schofield
                                         ---------------------------------------
                                         John T. Schofield, President and
                                         Chief Executive Officer (Principal
                                         Executive Officer)


                               POWER OF ATTORNEY

       KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints John T. Schofield and Steven J.
Guerrettaz, jointly and severally, as his attorneys-in-fact, with full power of
substitution in each, for him or her in any and all capacities to sign any
amendments to this Registration Statement on Form S-8, and to file the same,
with all exhibits thereto and other documents in connection therewith, with the
Securities and Exchange Commission, hereby ratifying and confirming all that
each of said attorneys-in-fact, or his substitutes, may do or cause to be done
by virtue hereof.

       Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed below by the following persons in the
capacities and on the dates indicated.
<TABLE>
<CAPTION>
 
         Signature                             Title                            Date
- --------------------------    --------------------------------------  ------------------------
<S>                           <C>                                       <C>
/s/ John T. Schofield         President, Chief Executive Officer and    September 19, 1996
- ---------------------------   Director (Principal Executive Officer)
(John T. Schofield)


/s/ Steven J. Guerrettaz      Vice President Finance and Accounting     September 19, 1996
- ---------------------------   and Chief Financial Officer (Principal
(Steven J. Guerrettaz)        Financial and Accounting Officer)


/s/ Robi Blumenstein          Director                                  September 19, 1996
- ---------------------------
(Robi Blumenstein)


/s/ Harry J. Healer, Jr.      Director                                  September 19, 1996
- ---------------------------
(Harry J. Healer, Jr.)


/s/ Rebecca Mark              Director                                  September 19, 1996
- ---------------------------
(Rebecca Mark)



- ---------------------------   Director                                  September 19, 1996
(Robert W. Page)
</TABLE> 

                                      II-4
<PAGE>
 
<TABLE> 
<S>                           <C>                                       <C>  

- ---------------------------   Director                                  September 19, 1996
(Frank R. Pope)


/s/ John M. Toups             Director                                  September 19, 1996
- ---------------------------
(John M. Toups)
</TABLE>

                                      II-5
<PAGE>
 
                               INDEX TO EXHIBITS

<TABLE>
<CAPTION>
 
 Exhibit Number                                        Description
 --------------     -------------------------------------------------------
 <C>                 <S>
      4.1*          Specimen Stock Certificate

      4.2*          Amended and Restated Investor Rights Agreement

      5.1           Opinion of counsel as to legality of securities being registered.

     10.2A*         1987 Incentive Stock Plan and form of Stock Option Agreement thereunder.

     10.3A*         1996 Stock Plan and form of Stock Option Agreement thereunder.

     10.4A*         Employee Stock Purchase Plan and forms of agreements thereunder.

     10.5*          1996 Director Option Plan and form of Director Stock Option Agreement thereunder.

     23.1           Consent of counsel (contained in Exhibit 5.1)

     23.2           Consent of Arthur Andersen LLP

     24.1           Power of Attorney (see page II-4)
</TABLE>
- ------------------------
*    Incorporated by reference to exhibits filed with the Company's Registration
     Statement on Form S-1 (file no. 333-4370), in the form declared effective
     on June 19, 1996.
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 21253}]
{"company-data": {"conformed-name": "THERMATRIX INC", "cik": "0000929473", "assigned-sic": "3569", "irs-number": "942958515"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-12363", "film-number": "96632498"}, "business-address": {"street1": "101 METRO DRIVE", "street2": "STE 248", "city": "SAN JOSE", "state": "CA", "zip": "95110"}}
AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON SEPTEMBER 19, 1996
                                                   REGISTRATION NO. 333-
=============================================================================== 

 
                      SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C. 20549

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

                                   FORM S-8
                            REGISTRATION STATEMENT
                                     UNDER
                          THE SECURITIES ACT OF 1933

                         ----------------------------
 
                                THERMATRIX INC.
              (EXACT NAME OF ISSUER AS SPECIFIED IN ITS CHARTER)
 
                         ---------------------------

       DELAWARE                                         94-2958515
  ------------------                                    ----------
(STATE OF INCORPORATION)                   (I.R.S. EMPLOYER IDENTIFICATION NO.)
 
                          101 METRO DRIVE, SUITE 248
                          SAN JOSE, CALIFORNIA 95110
                   (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)
 
                   ----------------------------------------

                           1987 INCENTIVE STOCK PLAN
                                1996 STOCK PLAN
                         EMPLOYEE STOCK PURCHASE PLAN
                           1996 DIRECTOR OPTION PLAN
                           (FULL TITLE OF THE PLAN)

                   ----------------------------------------
 
                               JOHN T. SCHOFIELD
                CHAIRMAN, PRESIDENT AND CHIEF EXECUTIVE OFFICER
                                THERMATRIX INC.
                          101 METRO DRIVE, SUITE 248
                          SAN JOSE, CALIFORNIA 95110
                                (408) 453-0490
(NAME, ADDRESS, AND TELEPHONE NUMBER, INCLUDING AREA CODE, OF AGENT FOR SERVICE)

                   -----------------------------------------
 
                                   Copy to:
                           ALISANDE M. ROZYNKO, ESQ.
                       WILSON SONSINI GOODRICH & ROSATI
                           PROFESSIONAL CORPORATION
                              650 PAGE MILL ROAD
                           PALO ALTO, CA 94304-1050
                                (415) 493-9300
 

================================================================================
CALCULATION OF REGISTRATION FEE
=========================================================================================
 
      Title of             Maximum            Proposed       Proposed       Amount of
     Securities             Amount            Maximum         Maximum      Registration
       to be                to be             Offering       Aggregate         Fee
     Registered            Registered         Price Per       Offering
                                                Share           Price
- ----------------------------------------------------------------------------------------
Common Stock,                                       
  $.001 par value...   746,997  shares(1)     $1.61 (2)     $1,202,665.17(2)    $  414.71
Common Stock,                                                       
  $.001 par value...   333,334  shares(3)     $8.25 (4)     $2,750,005.50       $  948.28
Common Stock,                                                       
  $.001 par value...   116,667  shares(5)     $8.25 (6)     $  818,127.34       $  282.11
Common Stock,                                        
  $.001 par value...    83,334  shares(7)     $8.25 (8)     $  857,514.00       $  295.69
          TOTAL        1,280,332  SHARES         --         $5,628,312.01       $1,940.80
=========================================================================================
(1)   For the sole purpose of calculating the registration fee, the number of
      shares to be registered under this Registration Statement has been broken
      down into four subtotals.  This subtotal represents the sum of shares
      issuable upon exercise of presently outstanding options (options that have
      been granted as of the date of this Registration Statement) issued under
      the 1987 Stock Plan.

(2)   Computed in accordance with Rule 457(h) under the Securities Act of 1933
      solely for the purpose of calculating the total registration fee.  This
      computation is based on the weighted average exercise price (rounded to
      nearest cent) at which the options outstanding whose exercise will result
      in the issuance of the shares being registered may be exercised.

(3)   This sub-total represents the sum of shares authorized to be issued under
      the 1996 Stock Plan.

(4)   Estimated in accordance with Rule 457(h) under the Securities Act of 1933
      solely for the purpose of calculating the total registration fee.  This
      computation is based upon the average of the high and low prices of the
      Common Stock as reported in The Nasdaq National Market on September 18,
      1996.

(5)   This sub-total represents the number of shares authorized to be issued
      under the Employee Stock Purchase Plan.

(6)   Estimated in accordance with Rule 457(h) under the Securities Act of 1933
      solely for the purpose of calculating the total registration fee.
      Computation based upon 85% (see explanation in following sentence) of the
      average of the high and low prices of the Common Stock as reported in The
      Nasdaq National Market on September 18, 1996.  Pursuant to the Employee
      Stock Purchase Plan, which plan is incorporated by reference herein, the
      purchase price of a share of Common Stock shall be an amount equal to 85%
      of the Fair Market Value of a share of Common Stock on the Enrollment Date
      or the Exercise Date (as defined in such Plan), whichever is lower.

(7)   This sub-total represents the number of shares authorized to be issued
      under the 1996 Director Option Plan  This sub-total includes 40,002 shares
      that were granted to the Directors on June 19, 1996 with a  exercise price
      of $12.50.  43,332 shares are available for issuance under the Director
      Option Plan.

(8)   Options were granted on June 19, 1996 to the Directors with a exercise
      price of $12.50.  Future Director option grants computation is based upon
      the average of the high and low prices of the Common Stock as reported in
      the Nasdaq National Market on September 18, 1996 because the price at
      which the options to be granted in the future may be exercised is not
      currently determinable.

                                     -ii-
THERMATRIX INC.
                      REGISTRATION STATEMENT ON FORM S-8

                                    PART II

                INFORMATION REQUIRED IN REGISTRATION STATEMENT
                                        
ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE
         ---------------------------------------

         There are hereby incorporated by reference in this Registration
Statement the following documents and information heretofore filed by Thermatrix
Inc. (the "Company") with the Securities and Exchange Commission:

         (1)  The Company's Registration Statement on Form S-1 (file no. 333-
4370) filed under the Securities Act of 1933, as amended (the "Securities Act"),
in the form declared effective on June 19, 1996.

         (2)  The description of the Company's Common Stock contained in the
Company's Registration Statement on Form 8-A filed May 1, 1996 pursuant to
Section 12(g) of the Securities Exchange Act of 1934, as amended (the "Exchange
Act") and declared effective on June 19, 1996.

         (3)  The Form 10-Q of the Registrant filed pursuant to Section 31(a) of
the Securities Exchange Act of 1934 (the "Exchange Act") on August 14, 1996.

         (4)  All documents filed by the Company pursuant to Sections 13(a),
13(c), 14 and 15(d) of the Exchange Act on or after the date of this
Registration Statement and prior to the filing of a post-effective amendment
which indicates that all securities offered have been sold or which deregisters
all securities then remaining unsold shall be deemed to be incorporated by
reference in this Registration Statement and to be part hereof from the date of
filing of such documents.

ITEM 4.  DESCRIPTION OF SECURITIES.
         ------------------------- 

         Not applicable.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.
         -------------------------------------- 

         As of the date hereof, certain members of Wilson, Sonsini, Goodrich &
Rosati, Professional Corporation beneficially owned a total of 8,940 shares of
the registrants Common Stock. Mario M. Rosati, the Assistant Secretary of the
Company, is a member of Wilson Sonsini Goodrich & Rosati.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.
         ----------------------------------------- 

         Section 145(a) of the Delaware General Corporation Law (the "DGCL")
provides in relevant part that "a corporation shall have power to indemnify any
person who was or is a party or is threatened to be made a party to any
threatened, pending or completed action, suit or proceeding, whether civil,
criminal, administrative or investigative (other than an action by or in the
right of the corporation) by reason of the fact that he is or was a director,
officer, employee or agent of the corporation, partnership, joint venture, trust
or other enterprise, against expenses (including attorneys' fees), judgments,
fines and amounts paid in settlement actually and reasonably incurred by him in
connection with such action, suit or proceeding if he acted in good faith and in
a manner he reasonably believed to be in or not opposed to the best interests of
the corporation, and, with respect to any criminal action or proceeding,
had no reasonable cause to believe his conduct was unlawful." With respect to
derivative actions, Section 145(b) of the DGCL provides in relevant part that
"[a] corporation shall have power to indemnify any person who was or is a party
or is threatened to be made a party to any threatened, pending or completed
action or suit by or in the right of the corporation to procure a judgment in
its favor . . . [by reason of his service in one of the capacities specified in
the preceding sentence] against expenses (including attorneys' fees) actually
and reasonably incurred by him in connection with the defense or settlement of
such action or suit if he acted in good faith and in a manner he reasonably
believed to be in or not opposed to the best interests of the corporation and
except that no indemnification shall be made in respect of any claim, issue or
matter as to which such person shall have been adjudged to be liable to the
corporation unless and only to the extent that the Court of Chancery or the
court in which such action or suit was brought shall determine upon application
that, despite the adjudication of liability but in view of all the circumstances
of the case, such person is fairly and reasonably entitled to indemnity for such
expenses which the Court of Chancery or such other court shall deem proper."

         The Company's Restated Certificate of Incorporation provides that to
the fullest extent permitted by the DGCL, no director of the Company shall be
personally liable to the Company or its stockholders for monetary damages for
breach of fiduciary duty as a director. The Certificate of Incorporation also
provides that no amendment or repeal of such provision shall apply to or have
any effect on the right to indemnification permitted thereunder with respect to
claims arising from acts or omissions occurring in whole or in part before the
effective date of such amendment or repeal whether asserted before or after such
amendment or repeal.

         The Company's Bylaws provide that the Company shall indemnify to the
full extent authorized by law each of its directors, officers, employees and
other agents against expenses actually and reasonably incurred in connection
with any proceeding arising by reason of the fact that such person is or was an
agent of the corporation.

         The Company has entered into indemnification agreements with its
directors and executive officers, in addition to indemnification provided for in
the Company's Bylaws, and intends to enter into indemnification agreements with
any new directors and executive officers in the future.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED.
         ----------------------------------- 

         Not applicable
 
ITEM 8.  EXHIBITS.
         --------
Exhibit                             Description
    Number
    -------     ----------------------------------------------------------------
4.1*      Specimen Stock Certificate

      4.2*      Amended and Restated Investor Rights Agreement

      5.1       Opinion of counsel as to legality of securities being registered.

     10.2A*     1987 Incentive Stock Plan and form of Stock Option Agreement
                thereunder.

     10.3A*     1996 Stock Plan and form of Stock Option Agreement thereunder.

     10.4A*     Employee Stock Purchase Plan and forms of agreements thereunder.

     10.5*      1996 Director Option Plan and form of Director Stock Option
                Agreement thereunder.

     23.1       Consent of counsel (contained in Exhibit 5.1).
II-2
Exhibit                             Description
    Number
    -------     ----------------------------------------------------------------
23.2       Consent of Arthur Andersen LLP
     24.1       Power of Attorney (see page II-4).
- ---------------
*     Incorporated by reference to exhibits filed with the Company's
      Registration Statement on Form S-1 (file no. 333-4370), in the form
      declared effective on June 19, 1996.

ITEM 9.  UNDERTAKINGS.
         ------------ 

    A.   The Company hereby undertakes:

         (1)  To file, during any period in which offers or sales are being
made, a post-effective amendment to this registration statement to include any
material information with respect to the plan of distribution not previously
disclosed in the registration statement or any material change to such
information in the registration statement.

         (2)  That, for the purpose of determining any liability under the
Securities Act, each such post-effective amendment shall be deemed to be a new
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

         (3)  To remove from registration by means of a post-effective amendment
any of the securities being registered which remain unsold at the termination of
the offering.

    B.   Insofar as indemnification for liabilities arising under the Securities
Act may be permitted to directors, officers and controlling persons of the
Company pursuant to the Corporation Law, the Company's Certificate of
Incorporation, the Company's Bylaws or the Company's indemnification agreements,
the Company has been advised that in the opinion of the Securities and Exchange
Commission such indemnification is against public policy as expressed in the
Securities Act and is therefore unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the Company
of expenses incurred or paid by a director, officer or controlling person of the
Company in the successful defense of any action, suit or proceeding) is asserted
by such director, officer or controlling person in connection with the
securities being registered hereunder, the Company will, unless in the opinion
of its counsel the question has already been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question of whether such
indemnification by it is against public policy as expressed in the Securities
Act and will be governed by the final adjudication of such issue.

                                      II-3
SIGNATURES

       Pursuant to the requirements of the Securities Act of 1933, the
Registrant, Thermatrix Inc., a corporation organized and existing under the laws
of the State of Delaware, certifies that it has reasonable grounds to believe
that it meets all of the requirements for filing on Form S-8 and has duly caused
this registration statement to be signed on its behalf by the undersigned,
thereunto duly authorized, in the City of San Jose, State of California, on this
19th day of September, 1996.

                                    THERMATRIX INC.

                                    By:  /s/ John T. Schofield
                                         ---------------------------------------
                                         John T. Schofield, President and
                                         Chief Executive Officer (Principal
                                         Executive Officer)

                               POWER OF ATTORNEY

       KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints John T. Schofield and Steven J.
Guerrettaz, jointly and severally, as his attorneys-in-fact, with full power of
substitution in each, for him or her in any and all capacities to sign any
amendments to this Registration Statement on Form S-8, and to file the same,
with all exhibits thereto and other documents in connection therewith, with the
Securities and Exchange Commission, hereby ratifying and confirming all that
each of said attorneys-in-fact, or his substitutes, may do or cause to be done
by virtue hereof.

       Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed below by the following persons in the
capacities and on the dates indicated.
Signature                             Title                            Date
- --------------------------    --------------------------------------  ------------------------
/s/ John T. Schofield         President, Chief Executive Officer and    September 19, 1996
- ---------------------------   Director (Principal Executive Officer)
(John T. Schofield)

/s/ Steven J. Guerrettaz      Vice President Finance and Accounting     September 19, 1996
- ---------------------------   and Chief Financial Officer (Principal
(Steven J. Guerrettaz)        Financial and Accounting Officer)

/s/ Robi Blumenstein          Director                                  September 19, 1996
- ---------------------------
(Robi Blumenstein)

/s/ Harry J. Healer, Jr.      Director                                  September 19, 1996
- ---------------------------
(Harry J. Healer, Jr.)

/s/ Rebecca Mark              Director                                  September 19, 1996
- ---------------------------
(Rebecca Mark)

- ---------------------------   Director                                  September 19, 1996
(Robert W. Page)
II-4
- ---------------------------   Director                                  September 19, 1996
(Frank R. Pope)

/s/ John M. Toups             Director                                  September 19, 1996
- ---------------------------
(John M. Toups)
II-5
INDEX TO EXHIBITS
Exhibit Number                                        Description
 --------------     -------------------------------------------------------
4.1*          Specimen Stock Certificate

      4.2*          Amended and Restated Investor Rights Agreement

      5.1           Opinion of counsel as to legality of securities being registered.

     10.2A*         1987 Incentive Stock Plan and form of Stock Option Agreement thereunder.

     10.3A*         1996 Stock Plan and form of Stock Option Agreement thereunder.

     10.4A*         Employee Stock Purchase Plan and forms of agreements thereunder.

     10.5*          1996 Director Option Plan and form of Director Stock Option Agreement thereunder.

     23.1           Consent of counsel (contained in Exhibit 5.1)

     23.2           Consent of Arthur Andersen LLP

     24.1           Power of Attorney (see page II-4)
- ------------------------
*    Incorporated by reference to exhibits filed with the Company's Registration
     Statement on Form S-1 (file no. 333-4370), in the form declared effective
     on June 19, 1996.