Gas flow control apparatus for an anaesthesia system

Apparatus for controlling the flow of gas to or from a patient in an anaesthesia system, said apparatus comprising a reservoir bag, a selector valve means operable in a first condition to connect said bag to said first flow passage, in a second condition to connect said bag to said second flow passage, and in a third condition to connect said bag to both of said first and second flow passages, said first and second flow passages being arranged in parallel and each being adapted to be connected at the end thereof remote from the selector valve means to a patient, said first passage comprising first one-way valve means selectively operable to prevent the back-flow of gas into said passage from the patient and communicating with an inlet for the supply of fresh gas, and said second flow passage comprising second one-way valve means selectively operable to prevent the flow of gas from said second flow passage to the patient and a selectively bypassable carbon dioxide absorbing means, there being a spill valve arranged to release gases from the second flow passage, wherein means are provided to control said conditions of the selector valve means and the selective operation of said first and second one-way valve means whereby desired modes of operation of the apparatus may be selected.