Abstract: A damper for use in controlling the flow rate or direction of a flow of air or fumes flowing out from a room or space or flowing through a ventilation system, including a housing having at least one inlet opening. The housing has a tubular side wall in which are provided a plurality of outlet apertures opened and closed by associated closure members which are adapted to swing to and away from the side wall, preferable inwardly of the housing. The total flow area of the outlet apertures may be extended to a desired degree by increasing the axial length and diameter of the side wall of the housing, whereby the flow resistance and pressure drop across the damper are reduced.