UNDERWATER DIVING METHOD AND SYSTEM COMPRISING BREATHING GAS CONTAINING HYDROGEN

PCT No. PCT/FR95/01083 Sec. 371 Date Feb. 19, 1997 Sec. 102(e) Date Feb. 19, 1997 PCT Filed Aug. 11, 1995 PCT Pub. No. WO96/06771 PCT Pub. Date Mar. 7, 1996A process of pressurization, of supply for effecting a dive for underwater intervention with a breathing mixture with hydrogen, and of decompression of a person making the dive, wherein the person is pressurized to an absolute pressure P1 of at least 0.45 MPa with a first type of breathing mixtures not containing hydrogen. The person is supplied at least from this pressure P1 with a second type of breathing mixtures at pressure P as a function of the depth of dive p to which said person is lowered, which second breathing mixture is of hydreliox type containing hydrogen at a minimum partial pressure of 0.33 MPa, oxygen at less than 4% by volume, helium with a partial pressure of more than 0.1 MPa and other gases such a nitrogen with a total partial pressure of less than 0.09 MPa. Supplying this second type of hydrogenated breathing mixtures in accordance with a composition which would locate the dive in one of the zones of the high pressure nervous syndrome or of narcosis is avoided. The supply of the hydreliox mixture thus obtained is maintained at the pressure P2 of the depth of dive p2 of the desired intervention and the person is authorized to make the desired intervention at this depth p2.