<PAGE>
                                                               EXHIBIT 10(i)A(2)

                       FIRST AMENDMENT TO CREDIT AGREEMENT


         THIS FIRST AMENDMENT TO CREDIT AGREEMENT (this "First Amendment") is
dated as of the 14th day of July, 2000 among NATIONAL SERVICE INDUSTRIES, INC.,
the other Borrowers parties hereto (collectively, the "Borrower"), the Banks
parties hereto (collectively, the "Banks"), BANK ONE, NA (formerly The First
National Bank Of Chicago), as Syndication Agent (the "Syndication Agent"),
WACHOVIA BANK, N.A., as Administrative Agent (the "Administrative Agent"; the
Syndication Agent and the Administrative Agent are collectively referred to as
the "Agents");

                                  WITNESSETH:

         WHEREAS, the Borrower, the Agents and the Banks executed and delivered
that certain Credit Agreement dated as of July 15, 1999 (the "Credit
Agreement");

         WHEREAS, the Borrower has requested and the Agents and the Banks have
agreed to certain amendments to the Credit Agreement, subject to the terms and
conditions hereof;

         NOW, THEREFORE, for and in consideration of the above premises and
other good and valuable consideration, the receipt and sufficiency of which
hereby is acknowledged by the parties hereto, the Borrower, the Agents and the
Banks hereby covenant and agree as follows:

         1.       Definitions. Unless otherwise specifically defined herein,
each term used herein which is defined in the Credit Agreement shall have the
meaning assigned to such term in the Credit Agreement. Each reference to
"hereof", "hereunder", "herein" and "hereby" and each other similar reference
and each reference to "this Agreement" and each other similar reference
contained in the Credit Agreement shall from and after the date hereof refer to
the Credit Agreement as amended hereby.

         2.       Amendment to Section 1.01. Section 1.01 of the Credit
Agreement hereby is amended by deleting the definition of "Termination Date" and
adding the following new definitions in the appropriate alphabetical sequence:

                  "Termination Date" means the earlier of (i) July 13, 2001, or
such later date to which it is extended by the Banks pursuant to Section
2.05(b), in their sole and absolute discretion, (ii) the date the Commitments
are terminated pursuant to Section 6.01 following the occurrence of an Event of
Default, or (iii) the date the Borrower terminates the Commitments entirely
pursuant to Section 2.08.

                  "Term Out Election" has the meaning set forth in Section

                  "Term Out Maturity Date" has the meaning set forth in Section

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<PAGE>

         3.       Amendment to Section 2.05(b). Section 2.05(b) of the Credit
Agreement hereby is deleted, and the following is substituted therefor:

                  (b)      Notwithstanding the foregoing, the outstanding
         principal amount of the Loans, if any, together with all accrued but
         unpaid interest thereon, if any, shall be due and payable on the
         Termination Date unless the Termination Date is otherwise extended by
         the Banks, in their sole and absolute discretion, provided, that in the
         event the Term Out Election is made pursuant and subject to the last
         (unlettered) paragraph of this Section 2.05(b), the outstanding
         principal amount of the Loans, together with all accrued but unpaid
         interest thereon, shall be due and payable on the Term Out Maturity
         Date. Upon the written request of the Borrower, which request shall be
         delivered to the Administrative Agent no more than 60 days, and not
         less than 30 days, prior to the then existing Termination Date, the
         Banks shall have the option (without any obligation whatsoever so to
         do) of extending the Termination Date for additional 364-day periods on
         each then existing Termination Date. Each Bank shall notify the
         Borrower and the Administrative Agent no more than 30 days, and not
         less than 20 days, prior to the then existing Termination Date whether
         or not it chooses to extend the Termination Date for such an additional
         364-day period (but any Bank which fails to give such notice within
         such period shall be deemed not to have extended); provided, that the
         Termination Date shall not be extended with respect to any of the Banks
         unless, on or before the then existing Termination Date, as to the
         Commitment of any Bank which gave notice that it chooses not to extend,
         or which is deemed pursuant to the foregoing not to have extended (any
         such Bank being a "Terminating Bank"), one of the following shall
         occur:

                           (i)      the remaining Banks shall purchase ratable
         assignments (without any obligation so to do) from such Terminating
         Bank (in the form of an Assignment and Acceptance) in accordance with
         their respective percentage of the remaining Aggregate Commitments;
         provided, that, such Banks shall be provided such opportunity (which
         opportunity shall allow such Banks at least 5 Domestic Business Days in
         which to make a decision) prior to the Borrower finding another bank
         pursuant to the immediately succeeding clause (ii); and, provided,
         further, that, should any of the remaining Banks elect not to purchase
         such an assignment, then, such other remaining Banks shall be entitled
         to purchase an assignment from any Terminating Bank which includes the
         ratable interest that was otherwise available to such non-purchasing
         remaining Bank or Banks, as the case may be, or

                           (ii)     the Borrower shall find another bank,
         acceptable to the Administrative Agent, willing to accept an assignment
         from such Terminating Bank (in the form of an Assignment and
         Acceptance) on or before the then existing Termination Date, or

                           (iii)    on the then existing Termination Date, the
         Borrower shall reduce the aggregate Commitments in an amount equal to
         the Commitment of any such Terminating Bank and pay all amounts due to
         such Terminating Bank at that time.

                  The Borrower shall have the right, at any time not more than
     60 days and not less than (x) 30 days before the then current Termination
     Date, if an extension of the Termination Date has not been requested by the
     Borrower pursuant to the foregoing provisions, or (y) 15 days before the
     then current Termination Date if an extension of the Termination Date has
     been requested by the Borrower but not extended by the Required Banks
     pursuant to the foregoing provisions, to notify the Administrative Agent
     and the Banks that it has elected


                                       2
<PAGE>

         (the "Term Out Election") to have the outstanding principal amount of
         the Loans, together with all accrued but unpaid interest thereon,
         become due and payable on the date (the "Term Out Maturity Date") which
         is 364 days after the Termination Date in effect on the date the Term
         Out Election is made. If the Term Out Election has been timely made:
         (1) the Commitments shall terminate on the Termination Date in effect
         on the date the Term Out Election was made, and no new Borrowings may
         be made thereafter, other than, during the period from the Termination
         Date until the Term Out Maturity Date, Borrowings made solely as
         Refunding Loans, with no new actual advances of money by the Banks (and
         such Refunding Loans during such period may be Euro-Dollar Borrowings
         or Base Rate Borrowings (but not Money Market Borrowings), subject to
         the terms and conditions pertaining to Borrowings of such types,
         provided, that no Interest Period may be selected which would extend
         beyond the Term Out Maturity Date); and (2) the Loans, together with
         all accrued but unpaid interest thereon, shall become due and payable
         on the Term Out Maturity Date.

         4.       Amendment to Section 5.01. Section 5.01 of the Credit
Agreement hereby is amended by deleting subsections (h), (i) and (j) thereof
(and all references to any such subsection and related definitions in other
portions of the Credit Agreement shall be ignored and no further force or
effect).

         5.       Amendment to Section 5.05. In order to amend clause (e)(ii)
thereof, Section 5.05 of the Credit Agreement hereby is deleted and the
following is substituted therefor:

                           SECTION 5.05. Consolidations and Mergers. Each
         Borrower agrees that it will not, nor will the Parent permit any
         Subsidiary to, consolidate or merge with or into any other Person,
         provided that if, after giving effect to any of the following, no
         Default will be in existence, (a) any Subsidiary may merge or
         consolidate with the Parent, if the Parent is the corporation surviving
         such merger, (b) any Borrower may merge or consolidate with any other
         Borrower, (c) any Subsidiary which is a Guarantor may merge or
         consolidate with any other Subsidiary which is a Guarantor, (d) any
         Subsidiary which is not a Borrower or Guarantor may merge or
         consolidate with any other Subsidiary which is not a Borrower or
         Guarantor, or with any other Subsidiary which is a Borrower or
         Guarantor, if the Borrower or Guarantor, as the case may be, is the
         corporation surviving such merger, and (e) any Borrower or Subsidiary
         may merge with another Person if (i) such Person was organized under
         the laws of the United States of America or one of its states, (ii) the
         corporation surviving such merger is a Borrower or a Subsidiary and
         (iii) immediately after giving effect to such merger, no Default shall
         have occurred and be continuing.

         6.       Replacement of Schedule 4.08. Schedule 4.08 to the Credit
Agreement hereby is deleted and the Schedule 4.08 attached hereto is substituted
therefor.

         7.       Restatement of Representations and Warranties. The Borrower
hereby restates and renews each and every representation and warranty heretofore
made by it in the Credit Agreement and the other Loan Documents as fully as if
made on the date hereof and with specific reference to this First Amendment and
all other loan documents executed and/or delivered in connection herewith.


                                       3
<PAGE>

         8.       Effect of Amendment. Except as set forth expressly
hereinabove, all terms of the Credit Agreement and the other Loan Documents
shall be and remain in full force and effect, and shall constitute the legal,
valid, binding and enforceable obligations of the Borrower. The amendments
contained herein shall be deemed to have prospective application only, unless
otherwise specifically stated herein.

         9.       Ratification. The Borrower hereby restates, ratifies and
reaffirms each and every term, covenant and condition set forth in the Credit
Agreement and the other Loan Documents effective as of the date hereof.

         10.      Counterparts. This First Amendment may be executed in any
number of counterparts and by different parties hereto in separate counterparts,
each of which when so executed and delivered shall be deemed to be an original
and all of which counterparts, taken together, shall constitute but one and the
same instrument.

         11.      Section References. Section titles and references used in this
First Amendment shall be without substantive meaning or content of any kind
whatsoever and are not a part of the agreements among the parties hereto
evidenced hereby.

         12.      No Default. To induce the Agent and the Banks to enter into
this First Amendment and to continue to make advances pursuant to the Credit
Agreement, the Borrower hereby acknowledges and agrees that, as of the date
hereof, and after giving effect to the terms hereof, there exists (i) no Default
or Event of Default and (ii) no right of offset, defense, counterclaim, claim or
objection in favor of the Borrower arising out of or with respect to any of the
Loans or other obligations of the Borrower owed to the Banks under the Credit
Agreement.

         13.      Further Assurances. The Borrower agrees to take such further
actions as the Agent shall reasonably request in connection herewith to evidence
the amendments herein contained to the Borrower.

         14.      Governing Law. This First Amendment shall be governed by and
construed and interpreted in accordance with, the laws of the State of Georgia.

         15.      Conditions Precedent. This First Amendment shall become
effective only upon execution and delivery (i) of this First Amendment by each
of the parties hereto, and (ii) of the Consent and Reaffirmation of Guarantor at
the end hereof by the Guarantor.


                       [SIGNATURES COMMENCE ON NEXT PAGE]


                                       4
<PAGE>

         IN WITNESS WHEREOF, the Borrower, the Agents and each of the Banks has
caused this First Amendment to be duly executed, under seal, by its duly
authorized officer as of the day and year first above written.

                                 NATIONAL SERVICE INDUSTRIES, INC.
                                 as Borrower                         (SEAL)



                                 By:
                                    --------------------------------
                                      Title:


                                 NSI LEASING, INC.
                                 as Borrower                          (SEAL)



                                 By:
                                    --------------------------------
                                      Title:


                                 NSI ENTERPRISES, INC.
                                 as Borrower                          (SEAL)


                                 By:
                                    --------------------------------
                                      Title:


                                       5
<PAGE>

                                 BANK ONE, NA (formerly The First National
                                 Bank Of Chicago), as Syndication Agent
                                 and as a Bank                        (SEAL)



                                 By:
                                    --------------------------------
                                      Title:


                                       6
<PAGE>

                                 WACHOVIA BANK, N.A.
                                 as Administrative Agent and
                                 as a Bank                            (SEAL)



                                 By:
                                    --------------------------------
                                      Title:


                                       7
<PAGE>

                                 ABN AMRO, N.V.
                                 as a Bank                           (SEAL)



                                 By:
                                    --------------------------------
                                      Title:


                                       8
<PAGE>

                                 COMMERZBANK AKTIENGESELLSCHAFT,
                                 NEW YORK BRANCH, as Co-Agent.
                                 and as a Bank                       (SEAL)



                                 By:
                                    --------------------------------
                                      Title:


                                       9
<PAGE>

                                 THE BANK OF NEW YORK
                                 as a Bank                             (SEAL)



                                 By:
                                    --------------------------------
                                      Title:


                                       10
<PAGE>

                                 BANK OF AMERICA, N.A.
                                 as a Bank                          (SEAL)



                                 By:
                                    --------------------------------
                                      Title:


                                       11
<PAGE>

                                 MELLON BANK, N.A.
                                 as a Bank                          (SEAL)



                                 By:
                                    --------------------------------
                                      Title:


                                       12
<PAGE>

                                 MORGAN GUARANTY TRUST COMPANY
                                 OF NEW YORK, as a Bank              (SEAL)



                                 By:
                                    --------------------------------
                                      Title:


                                       13
<PAGE>

                                 SUNTRUST BANK (formerly SunTrust
                                 Bank, Atlanta), as a Bank          (SEAL)



                                 By:
                                    --------------------------------
                                      Title:


                                       14
<PAGE>

                     CONSENT AND REAFFIRMATION OF GUARANTOR

         The undersigned, in its capacity as a Guarantor (i) acknowledges
receipt of the foregoing First Amendment to Credit Agreement (the "First
Amendment"), (ii) consents to the execution and delivery of the First Amendment
by the parties thereto and (iii) reaffirms all of its obligations and covenants
under the Guaranty Agreement dated as of July 15, 1999 executed by it, and
agrees that none of such obligations and covenants shall be affected by the
execution and delivery of the First Amendment.


                                 NATIONAL SERVICES INDUSTRIES, INC.
                                 as Guarantor                         (SEAL)



                                 By:
                                    --------------------------------
                                      Title:


                                       15
<PAGE>

                                  Schedule 4.08

                            NSI LIST OF SUBSIDIARIES

<TABLE>
<CAPTION>
                                                                                                 State or Other
                                                                                                 Jurisdiction
                                                                                                 of Incorporation
Subsidiary or Affiliate                              Principal Location                          or Organization
----------------------------------------------------------------------------------------------------------------
<S>                                                  <C>                                         <C>
C&G Carandini SA                                     Barcelona, Spain                            Spain
Castlight de Mexico, S.A. de C.V.                    Matamoros, Tamaulipas                       Mexico
Graham International B.V.                            Bergen op Zoom, Holland                     Netherlands
HSA Acquisition Corporation                          Columbus, Ohio                              Ohio
HSA Financing Corporation                            Tultitlan, Mexico City                      Mexico
Holophane S.A. de C.V.                               Tultitlan, Mexico City                      Mexico
Holophane Alumbrado Iberica S.r.l.                   Barcelona, Spain                            Spain
Holophane Australia Corporation Pty Ltd.             New South Wales, Australia                  Australia
Holophane Canada, Inc.                               Brampton, Ontario                           Canada
Holophane Europe Ltd.                                Milton Keynes, England                      United Kingdom
Holophane Foundation, Inc.                                                                       New York
Holophane Holding Company                            Columbus, Ohio                              Ohio
Holophane International, Inc.                        Bridgetown, Barbados                        Barbados
Holophane Lichttechnik GmbH                          Dusseldorf, Germany                         Germany
Holophane Lighting Ltd.                              Milton Keynes, England                      United Kingdom
Holophane Market Development Corp.                   Grand Cayman, Cayman Islands                British West Indies
Indies
ID Limited                                           Douglas, Isle of Man                        Isle of Man
Kem Europa B.V.                                      Bergen op Zoom, Holland                     Netherlands
Keplime B.V.                                         Bergen op Zoom, Holland                     Netherlands
Keplime Ltd.                                         London, England                             United Kingdom
Lithonia Lighting do Brasil Ltda.                    Sao Paulo, Brazil                           Brazil
Lithonia Lighting Mexico S.A. de C.V.                Monterrey, Nuevo Leon                       Mexico
Lithonia Lighting Servicios S.A. de C.V.             Monterrey, Nuevo Leon                       Mexico
Luxfab Ltd.                                          Milton Keynes, England                      United Kingdom
National Airline Laundry Services, LLC               Atlanta, Georgia                            Delaware
National Empire Manufacturing Co., Inc.              Atlanta, Georgia                            Georgia
National Service Industries, Inc.                    Atlanta, Georgia                            Georgia
         Unincorporated Operating Divisions:
                  Allen Envelope
                  Antique Street Lamps
                  Atenco Filing Systems
                  Atlantic Envelope Company
                  Austin Lighting Products
                  Enforcer Products
                  Gilmore Envelope
                  Holophane
                  Lithonia Lighting
                  Lyon Folder Company
                  MetalOptics
                  National Chemical
                  National Direct Source
                  National Dust Control Service
                  National Healthcare Linen Service
                  National Linen Service
                  National Uniform Service
                  Seaboard Printing Services
</TABLE>


                                       16
<PAGE>

<TABLE>
<S>                                                  <C>                                         <C>
                  Selig Chemical Industries
                  Zep Manufacturing Company
National Service Industries Canada
               Limited Partnership                   Calgary, Alberta                            Canada
NSI Canadian Ventures, Inc.                          Calgary, Alberta                            Canada
NSI Enterprises, Inc.                                Atlanta, Georgia                            California
         Unincorporated Operating Divisions:
                  Lithonia Hydrel
                  Lithonia Lighting
                  Lithonia Peerless
NSI Export Ltd.                                      Bridgetown, Barbados                        Barbados
NSI Holdings, Inc.                                   Montreal, Quebec, Canada                    Canada
NSI Insurance (Bermuda) Ltd.                         Hamilton, Bermuda                           Bermuda
NSI International Pty Ltd.                           Melbourne, Australia                        Australia
NSI Leasing, Inc.                                    Atlanta, Georgia                            Delaware
NSI Realty, L.P.                                     Atlanta, Georgia                            Texas
NSI Ventures, Inc.                                   Atlanta, Georgia                            Delaware
Productos Lithonia Lighting de
              Mexico, S.A. de C.V.                   Monterrey, Nuevo Leon                       Mexico
Produits de Maintenance et de Proprete
              Industrielle SARL                      Nogent-le-Roi, France                       France
Selig Company of Puerto Rico, Inc.                   Atlanta, Georgia                            Puerto Rico
South Insulation Co., Inc.                           Dallas, Texas                               Texas
The Austphane Trust
Unique Lighting Solutions Pty Ltd.                   New South Wales, Australia                  Australia
ZEP Belgium S.A.                                     Brussels, Belgium                           Belgium
ZEP Europe B.V.                                      Bergen op Zoom, Holland                     Netherlands
ZEP FRANCE S.A.R.L                                   Nogent-le-Roi, France                       France
Zep Industries S.A.S.                                Nogent-le-Roi, France                       France
Zep Industries, S.A. (formerly Zep S.A.)             Bern, Switzerland                           Switzerland
Zep Industries B.V. (formerly Chemical Specialties)  Bergen op Zoom, Holland                     Netherlands
Zep International Pty Ltd.                           Melbourne, Australia                        Australia
Zep Italia S.r.l.                                    Aprilia, Italy                              Italy
Zep Kem Italia S.r.l.                                Aprilia, Italy                              Italy
Zep Manufacturing B.V.                               Bergen Op Zoom, Holland                     Netherlands
</TABLE>


                                       17