Aircraft closed circuit breathing system

Claim 1

In a closed circuit breathing system for the distribution of oxygen to, and waste gases from, the respiratory organs of a vertebrate wherein a respirator adapted to be worn by the vertebrate is, by separate conduits, connected to and in flow communication with an enclosure defined by both impermeable wall area and permeable, nonporous wall area having a CO2/O2 permeability ratio of at least about 5 whereby exhaled breath from the vertebrate is transmitted from said respirator to said enclosure, is depleted in CO2 content and transmitted back to said respirator in a closed circuit and means are provided in flow communication with said closed circuit for introducing makeup oxygen thereto, the improvement comprising: means for selective operation of said closed circuit either as a variable pressure, constant volume system or as a constant pressure, variable volume system, said means comprising a compressor connected in series in said closed circuit and a flexible breathing bag located in flow communication with said closed circuit upstream of said compressor, said compressor having valve means located therein providing some flow path therethrough during either condition of selective operation.