Conversion of Supercritical Air Self-contained Breathing Apparatus (SCBA) for Diving Applications

"The proposed breathing apparatus makes uses of moderate pressure gases (?750 psi) and a low temperature (<-170¿C) to store a greater quantity of breathing gas in the same volume. Two hours of supercritical cryogenic breathing air will have the same volumeas one hour of 4500 psi compressed breathing air. The supercritical breathing gas is single phase so that it will feed identically in any attitude, unlike liquid air. This is particularly important for underwater work as the attitudes are extremelyvariable. Because of the moderate or higher pressure the system will supply gas at any useable depth of dive. Whenout of the water the apparatus may be used for full respiratory protection against airborne chemical or biological agents. In addition, due to the cryogenic storage of the air there is considerable cooling capacity to reduce heat stress in the user duringhot climate deployments or when wearing impermeable garments. For normal underwater operations the heat to warm the breathing gas will come from the surrounding water, whereas for hot environment and land operations the heat will be supplied by the usersbody. The metabolic energy and heat transfer from the surrounding water is transferred to the breathing gas before it is consumed.An added feature which could be investigated in the Phase I option would be the use a small heater to allow warming of the user in both cold water and in cold land operations. The supercritical