Available in fire and combination fire/smoke models, DFD, FD, and FSD Series Dampers are approved for installation in horizontal, non-concrete, fire rated barriers. Units can be specified for use in UL floor/ceiling design I503, which consists of 2-hour fire rated floor/ceiling assembly made from steel studs and gypsum board. Installation method simplifies difficult task designers and contractors face trying to protect duct penetrations at top and bottom of fire-rated building shafts.