mcr FID WING fire dampers are designed for installation at penetrations of day-to-day ventilation ductwork through the building walls and horizontal assemblies. Their purpose is to maintain the fire-resistance rating of a building component at a point where it is penetrated by ventilation or air-conditioning ducts. They also prevent spread of flame, smoke and combustion gasses to the parts of the building which are not on fire. During normal operation of the system, the damper blade remains in the open position. In the event of a fire, the damper blade moves to the closed position. The dampers must not work in systems exposed to dust, unless they are covered by a special, individually developed servicing and technical inspections program.