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


                               Envirotest Systems Corp.

                                         and

                             the Guarantors named herein

                                         and

                          First Trust National Association,

                                       Trustee

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


                             THIRD SUPPLEMENTAL INDENTURE


                             Dated as of January 30, 1996


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


                                     $125,000,000


                           9-5/8% Senior Subordinated Notes
                                       due 2003

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



    THIRD SUPPLEMENTAL INDENTURE dated as of January 30, 1996, among ENVIROTEST
SYSTEMS CORP., a Delaware corporation (the "Company"), ENVIROTEST TECHNOLOGIES,
INC., a Delaware corporation (the "Initial Guarantor"), REMOTE SENSING
TECHNOLOGIES, INC., a Delaware corporation ("RST"), ENVIROTEST PARTNERS, a
Pennsylvania partnership (f/k/a Envirotest/Synterra Partners) ("Envirotest
Partners"), ENVIROTEST ACQUISITION CO., a Delaware corporation ("Envirotest
Acquisition"), and SYSTEMS CONTROL, INC., a Washington corporation ("Systems
Control"), and FIRST TRUST NATIONAL ASSOCIATION, a National Association, as
Trustee.


                                       RECITALS

    WHEREAS, the Company, the Initial Guarantor and the Trustee entered into an
Indenture, dated as of April 1, 1993 (the "Original Indenture"), pursuant to
which the Company issued $125,000,000 in principal amount of 9-5/8% Senior
Subordinated Notes due 2003 (the "Securities") (capitalized terms used herein
without definition shall have the respective meanings ascribed to them in the
Indenture); and

    WHEREAS, the Company, the Initial Guarantor and the Trustee amended the
Original Indenture by entering into a First Supplemental Indenture dated as of
March 16, 1994 in accordance with Section 9.02 of the Original Indenture; and

    WHEREAS, the Company, the Initial Guarantor, RST, Envirotest Partners and
the Trustee amended the Original Indenture, as amended, by entering into a
Second Supplemental Indenture dated as of May 28, 1994 in accordance with
Section 9.01 of the Original Indenture (as so supplemented by the First
Supplemental Indenture and the Second Supplemental Indenture, the "Indenture");
and

    WHEREAS, on January 22, 1996, the Company formed and capitalized Envirotest
Acquisition as a wholly owned subsidiary; and

    WHEREAS, on January 30, 1996, Envirotest Acquisition acquired Systems
Control; and

    WHEREAS, Section 9.01 of the Indenture provides that the Company, the
Initial Guarantor and the Trustee may amend or supplement the Indenture without
the consent of any Holders in order to, among other things, add additional
Guarantors pursuant to Section 13.03 of the Indenture; and

    WHEREAS, the Company, the Initial Guarantor, the Trustee, Envirotest
Partners, RST, Envirotest Acquisition and Systems Control desire to amend the
Indenture without the consent of any Holders to add each of Envirotest
Acquisition and Systems Control as a Guarantor in accordance with Section 13.03
of the Indenture;



    NOW, THEREFORE, to comply with the provisions of the Indenture and in
consideration of the above premises, the Company, the Initial Guarantor,
Envirotest Partners, RST, Envirotest Acquisition, Systems Control and the
Trustee covenant and agree for the benefit of each other and for the equal and
proportionate benefit of the respective Holders of the Securities as follows:

                                      ARTICLE 1

    Section 1.01.  This Third Supplemental Indenture is supplemental to the
Indenture and does and shall be deemed to form a part of, and shall be construed
in connection with and as part of, the Indenture for any and all purposes,
including but not limited to discharge of the Indenture as provided in Article 8
of the Indenture.

    Section 1.02.  Envirotest Acquisition hereby expressly assumes the
obligations of a Guarantor under the Indenture from and after January 30, 1996,
and Systems Control hereby expressly assumes the obligations of a Guarantor
under the Indenture from and after January 30, 1996.

    Section 1.03.  This Third Supplemental Indenture shall become effective
immediately upon its execution and delivery by each of the Company, the Initial
Guarantor, Envirotest Partners, RST, Envirotest Acquisition, Systems Control and
the Trustee, it being understood that the obligations undertaken in Section 1.02
hereof shall become effective as of the dates indicated in such Section 1.02.


                                      ARTICLE 2

    Section 2.01.  Except as specifically modified herein, the Indenture and
the Securities are in all respects ratified and confirmed and shall remain in
full force and effect in accordance with their terms.

    Section 2.02.  Except as otherwise expressly provided herein, no duties,
responsibilities or liabilities are assumed, or shall be construed to be
assumed, by the Trustee by reason of this Third Supplemental Indenture.  This
Third Supplemental Indenture is executed and accepted by the Trustee subject to
all the terms and conditions set forth in the Indenture with the same force and
effect as if those terms and conditions were repeated at length herein and made
applicable to the Trustee with respect hereto.

    Section 2.03.  The laws of the State of New York shall govern this Third
Supplemental Indenture without regard to principles of conflicts of law.  The
Trustee, the Company, the

                                         -2-


Initial Guarantor, Envirotest Partners, RST, Envirotest Acquisition and Systems
Control agree to submit to the jurisdiction of the courts of the State of New
York in any action or proceeding arising out of or relating to this Third
Supplemental Indenture.

    Section 2.04.  The parties may sign any number of copies of this Third
Supplemental Indenture.  Each signed copy shall be an original, but all of such
executed copies together shall represent the same agreement.


                                      SIGNATURES

    IN WITNESS WHEREOF, the parties hereto have caused this Third Supplemental
Indenture to be duly executed, all as of the date first written above.

                                       COMPANY

                                       ENVIROTEST SYSTEMS CORP.


                                       By:       /s/ Raj Modi
                                          -------------------------------------
                                       Name:     Raj Modi
                                       Title:    Vice President


                                       INITIAL GUARANTOR

                                       ENVIROTEST TECHNOLOGIES, INC.


                                       By:       /s/ Raj Modi
                                          -------------------------------------
                                       Name:     Raj Modi
                                       Title:    Vice President


                                       ENVIROTEST PARTNERS

                                       By:  ENVIROTEST SYSTEMS CORP.,
                                            its general partner


                                       By:       /s/ Raj Modi
                                          -------------------------------------
                                       Name:     Raj Modi
                                       Title:    Vice President

                                         -3-


                                       REMOTE SENSING TECHNOLOGIES, INC.


                                       By:       /s/ C. Michael Alston
                                          -------------------------------------
                                       Name:     C. Michael Alston
                                       Title:    Vice President



                                       ENVIROTEST ACQUISITION CO.


                                       By:       /s/ C. Michael Alston
                                          -------------------------------------
                                       Name:     C. Michael Alston
                                       Title:    Secretary


                                       SYSTEMS CONTROL, INC.


                                       By:       /s/ C. Michael Alston
                                          -------------------------------------
                                       Name:     C. Michal Alston
                                       Title:


                                       TRUSTEE

                                       FIRST TRUST NATIONAL ASSOCIATION,
                                       as Trustee


                                       By:    /s/ Richard Prokosch
                                          -------------------------------------
                                       Name:  Richard Prokosch
                                       Title: Trust Officer



e:\rk\enviro\indentur\supp3.958

                                         -4-