Nailor Model 0722 Ceiling Dampers are for use in spherical purposes, in lieu of hinged door variety dampers in any UL/ULC floor/ceiling or roof/ceiling assembly with up to a 3 hour fire resistance ranking exactly where air ducts are authorized. Sizes out there are limited only through the procedure style and on-internet site House https://zanewocqe.blogdal.com/37396893/the-2-minute-rule-for-dampers-for-industrial-sector