Ceiling dampers are designed to function as a heat barrier in air handling openings penetrating fire resistive membrane ceilings. The Model Series 557RD has been especially designed and tested to provide protection and simple installation in specific design wood truss ceiling assemblies.

The 557RD assembly consists of a rectangular ceiling damper recessed in a fiberglass plenum (boot/register box) by others that accommodates a steel grille, register or diffuser.