Exhibit 10.21


               FOURTH AMENDMENT TO REVOLVING CREDIT LOAN AGREEMENT


     THIS AGREEMENT (the "Agreement") dated as of the 15th day of June, 2000,
between FLEET BANK, N.A., with offices at 1125 Route 22 West, Bridgewater, New
Jersey 08807 (the "Bank") and BARRINGER TECHNOLOGIES INC., a Delaware
corporation, with offices at 30 Technology Drive, Warren, New Jersey 07059
("BTI"), BARRINGER INSTRUMENTS INCORPORATED, a New Jersey corporation, with
offices at 30 Technology Drive, Warren, New Jersey 07059 ("BII"), and BARRINGER
RESEARCH LIMITED, a Canadian corporation with offices at 1730 Aimes Boulevard,
Mississauga, Ontario, Canada L4W IVI ("BRL").

                                   WITNESSETH:

     WHEREAS, BTI executed and delivered a revolving credit note to Bank in the
original principal balance not to exceed Five Million and 00/100 Dollars
($5,000,000) (the "Revolving Credit Line"); and

     WHEREAS, the advances under the Revolving Credit Line are made by Bank in
accordance with and subject to the terms, covenants, conditions and provisions
of the Revolving Credit Loan Agreement, dated as of March 13, 1998 (as further
amended herein and together with all prior amendments, the "Loan Agreement");

     WHEREAS, BTI and Bank modified the terms of the Loan Agreement pursuant to
a First Loan Modification Agreement, dated as of July 1, 1999 (the "First
Modification Agreement"), which among other things, added Digivision, Inc.
("Digivision"), as a guarantor of BTI's obligations under the Revolving Credit
Line and the Loan Agreement (collectively, together with all related documents,
the "Loan Documents");

     WHEREAS, BTI and Bank modified the terms of the Loan Agreement pursuant to
an Amendment to Revolving Credit Loan Agreement and Guaranty Agreement, dated as
of February 2, 2000 (the "Second Modification Agreement"), which among other
things, released Digivision as a guarantor of BTI's obligations under the Loan
Documents, and a Third Modification to Revolving Credit Loan Agreement, dated as
of May 30, 2000 (the "Third Modification Agreement"); and

     WHEREAS, BTI and Bank have agreed to further amend the terms and conditions
of the Loan Agreement upon the terms and conditions contained herein.

     NOW, THEREFORE, in consideration of the mutual covenants and conditions
contained herein and for other valuable consideration, the parties hereby agree
as follows:

     1. Preamble. Each and every part of the preamble hereof is incorporated
herein by reference as if set forth at length.

     2. Amendment of Loan Agreement.

          a. The following new sections are added:

               Section 8.13 Pledge to Federal Reserve. Lender may at any time
          pledge all or any portion of its rights under the Loan Documents
          including any portion of the Notes to any of the twelve (12) Federal
          Reserve Bank organized under Section 4 of the Federal Reserve Act, 12
          U.S.C. Section 341. No such pledge or enforcement thereof shall
          release Lender from its obligations under any of the Loan Documents.



<PAGE>


               Section 8.14 Participations. Lender shall have the unrestricted
          right at any time and from time to time, and without the consent of or
          notice to Borrowers or any Guarantors, to grant to one or more banks
          or other financial institutions (each a "Participant") participating
          interests in Lender's obligation to lend hereunder and/or any or all
          of the Loans held by Lender hereunder. In the event of any such grant
          by Lender of a participating interest to a Participant, whether or not
          upon notice to Borrower, Lender shall remain responsible for the
          performance of its obligations hereunder and Borrowers shall continue
          to deal solely and directly with Lender in connection with Lender's
          rights and obligations hereunder. Lender may furnish any information
          concerning Borrowers in its possession from time to time to
          prospective Participants, provided that Lender shall require any such
          prospective Participant to agree in writing to maintain the
          confidentiality of such information.

               b. Section 2.6 (Computation of Interest) is deleted and replaced
          with the following:

               SECTION 2.6 Computation of Interest. The interest on the amounts
          outstanding under the Loan shall be computed on the basis of a year of
          360 days for the actual number of days elapsed.

     3. Representations and Warranties. BTI represents and warrants to the Bank
that the statements, representations and warranties made by BTI in the Loan
Documents are true and correct in all material respects as of the date hereof.

     4. Affirmation. Except as expressly modified herein, the Loan Documents
remain in full force and effect in accordance with the terms thereof. BTI hereby
ratifies, confirms and approves all of the terms of the Loan Documents.

     5. Binding Effect. This Agreement shall be binding upon the parties hereto
and their successors and assigns.

     6. Governing Law. This Agreement shall be construed and enforced in
accordance with the laws of the State of New Jersey.

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<PAGE>

     IN WITNESS WHEREOF, the parties have executed this Agreement the day and
year first above written.


WITNESS/ATTEST:
BARRINGER TECHNOLOGIES INC.                  BARRINGER INSTRUMENTS INCORPORATED

By: /s/ RICHARD S. ROSENFELD                 By: /s/ RICHARD S. ROSENFELD
   -------------------------                     ------------------------------
   Name: Richard S. Rosenfeld                    Name: Richard S. Rosenfeld
   Title: VP Finance                             Title: VP Finance

Attest: /s/ KENNETH WOOD                     Attest: /s/ KENNETH WOOD
      ----------------------                        ---------------------------


BARRINGER RESEARCH LIMITED

By: /s/ STANLEY BINDER
   -------------------------
   Name: Stanley Binder
   Title: Director

Attest: KENNETH WOOD
      ----------------------


FLEET BANK, N.A.

By: /s/   CRAIG W. HEAL
   -------------------------
   Name:  Craig W. Heal
   Title: Director


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