US Patent 7413024 Self-closing vent assembly

A self-closing vent has its frame and a honeycomb screen coated with an intumescent material. When affixed to a wall with an opening the vent is normally open, allowing free flow of air through the opening, but when exposed to the heat of a fire, the intumescent material expands to close the vent, thereby preventing spread of the fire through the opening. The intumescent material preferably is FireFree 88, in a coating thickness of about 5 to 15 mils. In one preferred embodiment the vent opening is in a vehicle, between an engine compartment and a passenger space.