Ceiling Radiation Damper Boot is a 90 degree Register Boot with a Fire Damper in the rectangular outlet end that accommodates the Grill or Register. In event of fire, the fusible links securing the curtain will melt, causing the steel curtain to close off the outlet so that fire and smoke do not travel outside the ductwork into the conditioned space. Commonly specified in Multifamily construction projects including Apartments, assisted living, and mix use developments, the CRD Boots serve the same purpose as the Square framed Fire Damper Sleeve and assembly specified in the wall or ceilings in rectangular ductwork.