Portable breathing system

Abstract

A semiclosed-loop rebreathing system is provided for use in a hostile environment. The system is characterized by a packed bed regenerative heat exchanger providing two distinct temperature-humidity zones of breathing gas with one zone providing cool, relatively dry air and the second zone providing hot, moist air. Exhaled gas is passed through the packed bed regenerative heat exchanger to increase the temperature and humidity of the gas and is then passed through a sorbent cannister containing a lithium hydroxide bed to remove carbon dioxide. The carbon dioxide-free gas is then passed through the regenerative heat exchanger in the reverse direction to cool and dehumidify the gas to normal breathing conditions. Check valves between the heat exchanger and the sorbent cannister establish gas flow in a single direction through the lithium hydroxide bed and a flexible breathing bag interposed in the flow path prevents back pressure during inhalation/exhalation sequences. A dump valve is interconnected between the heat exchanger and the inlet side of the lithium hydroxide cannister and when the breathing bag is fully extended functions to vent a portion of the exhaled gas. An external oxygen supply and control unit provides make-up oxygen to offset oxygen losses incurred by dumping a portion of the system gas and losses by metabolic consumption. A wick assembly is interconnected to the sorbent cannister at the inlet side to remove moisture condensate prior to passing the carbon-dioxide laden gas through the lithium hydroxide bed.