Abstract: Breathing apparatus of the closed- or semi-closed-circuit type includes a carbon dioxide absorber (8) which creates troublesome heat in operation. Apparatus giving acceptable breathing gas temperature incorporates an evaporative cooler unit (20), and a pump utilizing the diaphragn plate (15) of the breathing bag (3), the pump inducing an air flow over the evaporative cooler unit.

Abstract: A lung ventilator which changes over automatically to provide either ventilation or to allow for natural breathing has an oxygen inlet (1) connected through a pressure regulator (2) and a flow regulator (4) to a reservoir (7). A secondary supply to the reservoir (7) takes place through a NOT unit (10). Oxygen from the reservoir (7) is supplied to a face mask connection (29) either through a demand valve (34) or through a second flow regulator (18) and a spool valve (26). The spool valve (26) is controlled by a pneumatic timing system (20-25) and the oxygen from the reservoir either flows intermittently through the spool valve (26) which is opened and closed by the timing system to provide ventilation or, it is supplied through the demand valve (34). Changeover from one supply to the other and back again is controlled in dependence upon the pressure in the reservoir (7).