Airgas, Inc., Radnor, PA, has acquired Central Welding Supply Inc., an industrial packaged gas distributor with three locations south of Dallas, TX.  ; Also effective Nov. 1, 2007, it has acquired Texas Industrial Gas Inc., with one location in Houston, TX.   ; Both acquired businesses, which generated nearly $6 million in revenues in calendar 2006, have been integrated with Airgas Southwest, one of the regional companies within Airgas. The transactions bring the total number of acquisitions by Airgas in fiscal 2008 to 10, with acquired annual sales of $400 million.   ; 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 distributor of safety products, a producer of nitrous oxide and dry ice, and a liquid carbon dioxide producer in the Southeast, and distributor of process chemicals, refrigerants, and ammonia products.