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In underwater diving activities such as saturation diving, technical diving and nitrox diving, the maximum operating depth (MOD) of a breathing gas is the depth below which the partial pressure of oxygen (pO 2) of the gas mix exceeds an acceptable limit.
Saturation diver working on the USS Monitor wreck at 70 m (230 ft) depth Saturation diver conducting deep-sea salvage operations. Saturation diving is diving for periods long enough to bring all tissues into equilibrium with the partial pressures of the inert components of the breathing gas used.
Gas fraction is constant for the components of a mixture, but partial pressure changes in proportion to changes in the total pressure. Partial pressure is a useful measure for expressing limits for avoiding nitrogen narcosis and oxygen toxicity. [6] Dalton's law describes the combination of partial pressures to form the total pressure of the ...
If the brain used more oxygen than is available in the blood supply, the cerebral oxygen partial pressure may drop below the level required to sustain consciousness. This type of blackout is likely to occur early in the dive. [27] [29] Ascent-induced hypoxia is caused by a drop in oxygen partial pressure as ambient pressure is reduced on ascent ...
[1] [2] [12] [13] A maximum oxygen partial pressure of 1.4 bar for the active sectors of the dive, and 1.6 bar for decompression stops is recommended by several recreational and technical diving certification agencies for open circuit, [14] and 1.2 bar or 1.3 bar as maximum for the active sectors of a dive on closed-circuit rebreather ...
Inert gas such as nitrogen or helium continues to be taken up until the gas dissolved in the diver is in a state of equilibrium with the breathing gas in the diver's lungs, at which point the diver is saturated for that depth and breathing mixture, or the depth, and therefore the pressure, is changed, or the partial pressures of the gases are ...
In open circuit scuba the upper limit for oxygen partial pressure is generally accepted as 1.6 bar, [37] equivalent to a depth of 6 msw (metres of sea water), but in-water and surface decompression at higher partial pressures is routinely used in surface supplied diving operation, both by the military and civilian contractors, as the ...
Breathing mixtures for diving must limit partial pressure of oxygen to avoid the risk of acute oxygen toxicity, Recreational technical divers generally limit partial pressure of oxygen at the maximum planned depth of a dive to approximately 1.4 bar. When diving to depths below 57 m this requires the use of breathing gases with less than 21% oxygen.