With the progress of technology, the environmental pressure range of human being's activities are extended from 0 Pa (in the space) to 66 MPa (in the deep sea). The methods of penetration in the sea can be classified into two main groups, 1. Environmental pressure diving: the divers' body is exposed directly to the hydrostatic pressure depending on the dive depth, 2. Atmospheric diving: the operators stay under atmospheric air environment within the pressure hull (one-atmospheric diving suit or research submersible, Fig.1). Environmental pressure deep diving, the diver must respire the pressurized gas, He-O_2 or H_2-He-O_2 mixed gas. The sea water temperature goes down to a several degrees Celsius deeper than 200m, then the diver utilize the hot water suit and the inspired gas heater avoiding the respiratory heat loss. Without inspired gas heating system, the diver's body is directly cooled from the body core by their respiration.
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