AIR CURTAINS ( AIR DOOR , VENTILATION DOOR , CURTAIN DOOR , AIR CONDITONING PROTECTOR , HEATING PROTECTITIVE MACHINE , ... ) are designed for installation in shops, office buildings, hotels and restaurants doorway. They discharge a curtain of air, which effectively shut out outside air. Use them to keep out insects, unpleasant smells, and dust from indoor where a large number of people pass in and out. These air curtains also prevent air escaping from an air-conditioned room.