Abstract: An automatic opening smoke vent door is provided which serves as a normal, self-closing exit door, and which is capable of being connected to a fire alarm circuit so that the door opens automatically in the event of a fire to allow smoke to be vented. The invention provides a member, preferably an L-shaped sub-frame, hinged to the normal door frame, and with an opening device acting between the door frame and the hinged member to urge this member from a closed position to an open position disposed at about 90.degree. to the door frame. The hinged member is normally held in the closed position by a solenoid operated latch, which is released to allow the member to open in the event of a fire. The door is itself hinged to the hinged member, and a normal door closer is connected between the hinged member and the door to allow the door to operate in the usual way when the hinged member is in the closed position.