I have a situation where nitrogen and carbon dioxide (both compressed gas state) distribution piping is to be routed in a ceiling space in which the dropped ceiling tiles are sealed to the frames with gaskets (biopharm application). Is there an industry or manufacturer recommendation that this distribution piping should be welded/soldered in lieu of compression and/or threaded fittings? The vertical space between the dropped ceiling tile and the overhead concrete floor deck is about 3 ft. HVAC is fully ducted supply and return, so the space is unventilated. Please advise. Best Regards, Raymond A. Phillips Mechanical Engineer Process Results, Inc. 734-260-1639 rphillips@processresults.com