Exhibit 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the quarterly report of Airgas, Inc. (the “Company”) on Form 10-Q for the period ended June 30, 2015 as filed with the Securities and Exchange Commission (the “Report”), I, Peter McCausland, Executive Chairman of the Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that, to such officer’s knowledge:

(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 Company as of the dates and for the periods expressed in the Report.

 /s/ PETER McCAUSLAND

Peter McCausland

Executive Chairman

(Co-Principal Executive Officer)

August 5, 2015

The foregoing certification is being furnished to the Securities and Exchange Commission pursuant to 18 U.S.C. Section 1350 as an exhibit to the Report and is not being filed as part of the Report or as a separate disclosure document.