Nailor Design 0722 Ceiling Dampers are for use in spherical apps, in lieu of hinged door type dampers in almost any UL/ULC ground/ceiling or roof/ceiling assembly with as much as a 3 hour fireplace resistance ranking where air ducts are allowed. Wall and roof-mounted dampers are placed on mechanical HVAC ventilation methods. Commonly Employed https://heavy-duty-stainless-stee13445.activoblog.com/42791695/heavy-duty-stainless-steel-damper-manufacturers-an-overview