Airgas, Inc., Radnor, PA, has acquired Lehner & Martin, Inc, a Santa Ana, CA-based industrial gas and welding supply distributor with branches in Placentia, Gardena, and Chino, CA. L & M had sales of more than $13 million in the fiscal year ended March 31, 2007.   ; The operations have been integrated into Airgas West, one of the regional companies that make up Airgas' distribution business.   ; The transaction was the fifth acquisition completed since the start of Airgas' fiscal 2008 on April 1, 2007, with acquired sales now topping $378 million, including the Linde U.S. packaged gas acquisition announced earlier.   ; Airgas, Inc. is a U.S. distributor of industrial, medical, and specialty gases, and hardgoods, such as welding equipment and supplies. Airgas is also a U.S. distributor of safety products, U.S. producer of nitrous oxide and dry ice, a liquid carbon dioxide producer in the Southeast, and a distributor of process chemicals, refrigerants, and ammonia products.