Breathing apparatus

摘要

A portable breathing apparatus for use in a noxious atmosphere includes a helmet that is closed except for a bottom opening that is provided with a neck seal to permit the helmet to be slipped over the head of the wearer while sealing the open bottom of the helmet to provide an airtight enclosure about the wearer's head. A backpack includes a high pressure oxygen cylinder, that is connected to a regulator valve through a pressure reducer; and a carbon dioxide scrubber, that receives expiration gas from the helmet through an exhaust breathing line which connects to a flexible reservoir which collects the majority of expired gases and which is provided with a relief valve to protect the bag and limit expiration resistance. The outlet of the reservoir is connected to the inlet of the scrubber and the outlet of the scrubber being connected to a second inlet in the regulator valve by a line that includes a heat exchanger associated with the oxygen cylinder so that the oxygen cylinder removes heat from the recirculating gas from the carbon dioxide scrubber. The regulator valve has an outlet chamber connected to the helmet interior through an inlet breathing line and the regulator valve includes an on-off-type valve that delivers oxygen from the oxygen supply to the chamber through an injection nozzle only when inhalation by the wearer causes a pressure drop in the chamber that acts on a diaphragm to open the valve. The gas from the scrubber enters the chamber in a reduced pressure zone adjacent the nozzle outlet, the reduced pressure helping to pull scrubbed gases from the carbon dioxide scrubber.