Abstract: A breathing bag for inclusion in an open-circuit respirating system in which anaesthetic gases are supplied from an inlet duct (10) to a mask connected at (11). The bag (13) is connected at one end to a flexible exhalation duct (12), and has an open tail (14) as an escape passageway at the other end. An internal rod (21) connects the bag (13) pivotally to a ball and socket joint (22, 23) mounted on a rigid sleeve (25) adapted for connection to a scavenging system. A flexible bellows (27) adjustably surrounds the tail (14) thus to enable ready connection and disconnection of the rod (21) and sleeve (25) while being extendible to minimise or prevent the escape (at 17) of anaesthetic gases to the atmosphere.