A vacuum cleaning head includes a rotatable brush bar and an air turbine driving the brush bar. An air inlet admits air to drive the turbine. A button is movable between an open position, in which it admits air to the turbine, and a closed position in which it closes the inlet and prevents air from reaching the turbine. The button is movable in response to the speed of rotation of the turbine or to the flow of air to or through the turbine exceeding a predetermined limit.