A COLLAPSIBLE VENTILATION SYSTEM FOR VENTILATING OR EXHAUSTING AN AIR SPACE WHEREIN THE SYSTEM HAS AN INFLATABLE AND COLLAPSIBLE DUCT SECURED IN COMMUNICATING RELATIONSHIP TO AN EXHAUST DUCT LOCATED ABOVE THE AIR SPACE. A DRUM AND CABLE ARRANGEMENT DRIVEN BY AT LEAST ONE MOTOR IS CONNECTED TO THE LOWER PORTION OF THE INFLATABLE DUCT FOR RAISING AND LOWERING THE DUCT, AND MEANS ARE PROVIDED FOR SUPPLYING AIR TO THE DUCT TO INFLATE IT INTO POSITION. PREFERABLY, HEATED AIR IS USED TO PREVENT UNDESIRABLE CONDENSATION IN THE DUCT WHEN USED IN A RELATIVELY COOLER AMBIENT ATMOSPHERE.