An air supply system and valve is disclosed which provides a reverse pulse of air for cleaning a filter element located in a filter house. A valve is also disclosed for use in the air supply system. The system includes a pressure vessel adapted to contain a volume of compressed air to be used for supplying the reverse pulse, the pressure vessel having a wall with at least one outlet aperture therein. The valve is mounted to the wall around the aperture to control the flow of air from the pressure vessel, the valve means comprising a valve body having an inlet, an outlet and a flow passage connecting the inlet and outlet, the inlet, the outlet and the flow passage generally extending axially through the valve body, a valve seat surrounding the flow passage, and a valve closure member movable towards and away from the valve seat into closed and open positions to thereby close or open the flow passage, and operating means for moving the valve closure member between the closed and open positions. A conduit mounted to the valve body around the outlet and adapted to extend into the filter house in use so as to direct a pulse of air towards a filter element to be cleaned when the valve closure member is in the open position.