Dating scuba tanks
Oxygen has historically been obtained by fractional distillation of liquid air, but is increasingly obtained by non-cryogenic technologies such as pressure swing adsorption (PSA) and vacuum swing adsorption (VSA) technologies.The minimum safe partial pressure of oxygen in a breathing gas is commonly held to be 16 k Pa (0.16 bar).The associated risks are oxygen toxicity at depth and fire, particularly in the breathing apparatus.where the oxygen content is less than that of air, generally to the extent that there is a significant risk of measurable physiological effect over the short term.The immediate risk is usually hypoxic incapacitation at or near the surface.It causes nitrogen narcosis in the diver, so its use is limited to shallower dives. Equivalent air depth is used to estimate the decompression requirements of a nitrox (oxygen/nitrogen) mixture.Equivalent narcotic depth is used to estimate the narcotic potency of trimix (oxygen/helium/nitrogen mixture).A breathing gas is a mixture of gaseous chemical elements and compounds used for respiration.Air is the most common, and only natural, breathing gas.
As oxygen supports combustion and causes rust in diving cylinders, it should be handled with caution when gas blending.
If the body is deprived of oxygen for more than a few minutes, unconsciousness and death result.
The tissues and organs within the body (notably the heart and brain) are damaged if deprived of oxygen for much longer than four minutes.
Breathing gases for diving are classified by oxygen fraction.
The boundaries set by authorities may differ slightly, as the effects vary gradually with concentration and between people, and are not accurately predictable.where the oxygen content exceeds atmospheric levels, generally to a level where there is some measurable physiological effect over long term use, and sometimes requiring special procedures for handling due to increased fire hazard.