Magnetically actuated auto-closing air vent

A self-closing vent intended for use in attics, crawl spaces, joist cavities, exterior walls, interior walls, or other structural element which allows for the free flow of air from outside a building to interior spaces during normal use. The vent includes a damper blade pivotally connected to, and disposed within, the vent housing, which is held in an open position by a temperature sensitive fusible link. Two, and preferably three, permanent magnets provide the force for driving the damper blade into a closed and locked position. A first magnet disposed in a side of the vent housing and a second magnet disposed on the damper blade are disposed with opposing (repelling) polarities when the damper blade is held in the open position. A third magnet disposed proximate the back of the vent housing is oriented so as to attract the magnet disposed on the damper blade. Thus, when the fusible link is broken by high temperatures, the first magnet propels the damper blade toward the closed position, and the third magnet attracts the damper blade to assist in putting it into a fully closed position. The third magnet and second magnet then cooperate to effect a secure closure, which is supplemented by mechanical locks disposed in the vent housing.