A ventilation system to deliver conditioned air through a duct (10) to an enclosure includes a damper blade (12) rotatably mounted within the duct to regulate the flow of air to the enclosure. The ends of the damper blade (12) are in spaced relation to a pair of cutoff plates (14, 16) attached to the inner surface of the duct (10), except when the blade (12) is rotated to place each end thereof into contact with one of the plates (14, 16) to substantially interrupt all flow of conditioned air through the duct (10). The centre of curvature (26) of a curved portion (20) of the blade (12) is offset from the axis of rotation (13) thereof. IMAGE
展开▼