Abstract: The present invention relates to an arrangement for controlling fluid flow through an aperture.In one embodiment, the flow control arrangement, which may be used in association with a window to control the flow of ventilating air, comprises a strip brush composed of an array of resilient filaments firmly mounted at their root region. The free end region of the filaments define, with a fixed flange, the effective area or width of an aperture for the passage of ventilating air. Variations in the strength of the air flow incident to the array of filaments causes changes in the degree of deflection of the filaments, thus altering the effective width of the aperture and controlling the air flow through the aperture.