Active diver thermal protection requirements for cold water diving

An analysis of the supplemental heating requirements for military divers, both surface-tended and free-swimming, is presented. Specific categories of diver heat loss, including respiratory losses and suit convective losses, are characterized over a range of water temperatures, depths, and breathing gas mixtures. The need for a 1-kW diver heater is identified to accommodate deep dives where the limitation of a surface-supplied hot water source and a long hot water umbilical pose an unacceptable burden. A 0.5-kW heater is shown to be satisfactory to extend the performance of existing closed circuit-breathing apparatuses for shallow water operations in water temperatures as low as 40 degrees F. Substantial benefits in heat savings are shown through the use of passive regenerative breath heaters and alternative suit inflation gases for drysuit use.