Chimney fitted with extension and fan - incorporates collar to reduce noise emitted by fan unit

摘要

The chimney (5) is fitted with an extension (1) which has a fan (2) mounted above its upper end. The fan (2) is so mounted that there is a narroe gap (10) between it and the extension (1). The extension (1) is fitted with a collar (3) of L-shaped cross-section which extends around the perimeter of the chimney extension. This collar (3) is aligned with the gap (10) and its height is greater than the width of the gap (10). The collar reduces the noise emitted from the chimney when the fan is operating. The noise may be further reduced by covering the collar with a layer of sound reflecting or absorbing material.