Nailor Design 0722 Ceiling Dampers are for use in round purposes, in lieu of hinged door form dampers in almost any UL/ULC flooring/ceiling or roof/ceiling assembly with around a 3 hour fireplace resistance score wherever air ducts are permitted. Industrial dampers utilize a heavy-duty flanged body damper with many blade types and force classes. https://heavydutystainlesssteelda13445.verybigblog.com/35899250/the-definitive-guide-to-dampers-for-industrial-sector