a vent assembly for rapidly depressurizing a compartment in an aircraft upon accidental depressurization of another compartment , including an apertured grille through which a circulation of return air normally passes , but which is mounted to swing into a hollow wall of the aircraft to pass a greatly increased flow of depressurizing air into the wall when desired . two actuator plates are hinged together for differential pressure induced relative pivotal movement , and act upon such movement to swing the grille to its open or venting position . the hinged plates form a wall of a plenum chamber behind the grille , and the normal circulation of return air is so directed as to flow first through the grille , then through the plenum chamber , and then into the interior of the hollow wall beyond the plenum chamber to thereby assure positive and direct exposure of the plates to a change in compartment pressure .