Abstract: A flow control valve (100;200;300) for a ventilation or exhaust duct comprises a housing (102;202;302), which defines a longitudinally extending passage (104;204;304) between a flow inlet and a flow outlet. A closing element (110;210;310) in the passage is movable between a fully open position and a fully closed position. A motor or actuator (116;216;316) is provided for moving the closing element. The motor or actuator may be located inside the closing element (110;210;310). The flow passage (104;204;304) through the housing may have sections of different diameters to obtain a venturi-like diffusor. A pressure difference sensor may be provided, which in combination with a position of the closing element allows for computation of the flow rate through the valve without the need for a separate flow meter.