An air-flow valve (1) having associated therewith at least one movable blade (13) means for detecting air-flow thereabout, which valve (1) includes at least one air-directing aperture (5), said aperture being adapted to alter the direction of air-flow incident on said valve (1) from a first direction tangential to a second altered direction, which second altered direction is perpendicular or at least towards the planar surface of said blade (13) means; whereby said direction-altered air-flow provides a force which causes said blade means (13) to move.
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