Abstract: Contaminated air in general anaesthesia is extracted via a hemispherical hood 1 located closely over the patient. The hood 1, which is of a thin-wall transparent-shell form, is mounted for hand-touch variation of its orientation on an arm 2 which is carried by a telescopic column 3 that allows for height adjustment. The arm 2 extends from a unit 18 that allows the hood 1 to be swung horizontally about the column 3, and gas is drawn from the hood 1 near its open mouth 6 via a low-down port 7 (FIGS. 3 to 5) that is coupled through the arm 2 and column 3 to a fan unit 4. Relief 23 of the bottom margin of the hood 1 may be used to enhance access to the patient, and for maneuverability the column 3 is trolley-mounted or adjustable laterally on a fixed track 35 (FIGS. 9 and 10).