Abstract: An air extract method and apparatus particularly for use with fume cupboards. The interior of the fume cupboard is connected to a suction fan via ducting and in the ducting is provided a connection to the outside atmosphere controlled by a baffle. The baffle position reduces the flow of air from the fume cupboard as it increases the flow from outside and vice versa, the position of the baffle being controlled by a servo motor or pneumatic cylinder operated by means responsive to the position of the sash window on the fume cupboard. Raising the sash window increases the air flow from the fume cupboard as it reduces the flow from outside, so that the velocity of air fow through the window aperture is always above a minimum and the exhaust velocity from the fan is also maintained.