Abstract: A vent structure for equalizing the pressure on opposite sides of a structure including a plenum formed at least in part by movable vent panel and a hinged panel supporting wall having overcenter biasing means, the plenum being pneumatically connected to the side of the structure which will be the high pressure side so that the condition requiring venting applies a differential pressure across the hinged wall which tends to force it overcenter against the overcenter biasing means thereby removing the normal support from the vent panel which moves to open a vent passageway. Spring-loaded flapper doors may be included in the plenum forming structure to enable relief of pressure in the opposite direction.

Abstract: A vent structure for equalizing the pressure on opposite sides of a structure including a plenum formed at least in part by movable vent panel and a hinged panel supporting wall having overcenter biasing means, the plenum being pneumatically connected to the side of the structure which will be the high pressure side so that the condition requiring venting applies a differential pressure across the hinged wall which tends to force it overcenter against the overcenter biasing means thereby removing the normal support from the vent panel which moves to open a vent passageway. Spring-loaded flapper doors may be included in the plenum forming structure to enable relief of pressure in the opposite direction.