Abstract: An apparatus for ventilating spacious public rooms, workshops, industrial halls, underground parking lot and the like spaces, which apparatus comprises a damper having a plurality of shutters attached by a ring to inner surface of tubular body so as to radially move a series of shutters from shut position to opened position. The apparatus further comprises a nozzle having a plurality of guide vanes which occur swirls in jet as well as in injected ventilation air supplied to the rooms. With this arrangement, the apparatus is effective for obtaining a precise adjustment of supply air with minimum air resistance, non-turbulent, and protecting dwelling zones against undesirable thermal air streams or undesirable radiation.