Ceiling dampers are designed to function as a heat barrier in air handling openings penetrating fire resistive membrane ceilings. The model 509 has been especially designed to provide protection and simple installation inspecific design wood truss ceiling assemblies.

The 509 assembly consists of a rectangular ceiling damper recessed in an internally insulated sheet metal register box (boot) with a round 90° side inlet collar, that accommodates a steel grille or register.