Abstract: A winch operating a drum around which a control cable is wound, the control cable controlling the opening and closing of shutters and smoke exhaust vents. The drum is driven by a gear train which may be immobilized by an electromagnetic brake or lock, such that the shutters or vents may be held closed or open, or in any intermediary position. In addition, the drum is provided with a ratchet wheel which can be immobilized by a solenoid operated rod. The electromagnetic brake or lock and the solenoid operating the ratchet wheel rod are controlled by push-buttons, and an emergency control is provided for releasing simultaneously the ratchet wheel and the electromagnetic brake or lock, such as to operate the drum for instantaneously opening the shutters and air vents to evacuate smoke and gases from the building.