Ceiling dampers are designed to function as a heat barrier in air handling openings penetrating fire resistive membrane ceilings . M o d e l 556RD has been especially designed to provide protection and simple installation in specific design wood truss ceiling assemblies.

The 556RD assembly consists of a rectangular ceiling damper recessed in a sheet metal register box (boot) by others with a round inlet collar, that accommodates a steel grille register or diffuser.