EXHIBIT 99.2 CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002 Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 and in connection with the Annual Report on Form 10-K of National Service Industries, Inc. (the "Corporation") for the fiscal year ended August 31, 2002, as filed with the Securities and Exchange Commission on the date hereof (the "Report"), the undersigned, the Senior Vice President, Chief Financial Officer and Treasurer certifies that: (1) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and (2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Corporation. /s/ Chester J. Popkowski - -------------------------------------- Chester J. Popkowski Senior Vice President, Chief Financial Officer and Treasurer November 15, 2002