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The limiting oxygen concentration (LOC), [1] also known as the minimum oxygen concentration (MOC), [2] is defined as the limiting concentration of oxygen below which combustion is not possible, independent of the concentration of fuel. It is expressed in units of volume percent of oxygen. The LOC varies with pressure and temperature.
The type of oxygen sensor used in most underwater diving applications is the electro-galvanic oxygen sensor, a type of fuel cell, which is sometimes called an oxygen analyser or ppO 2 meter. They are used to measure the oxygen concentration of breathing gas mixes such as nitrox and trimix . [ 9 ]
There are two commonly used ways to specify expected sensor life span: The time in months at room temperature in air, or volume percentage oxygen hours (Vol%O 2 h). Storage at low oxygen partial pressure when not in use would seem an effective way to extend cell life, but when stored in anoxic conditions the sensor current will cease and the ...
Safe limits for mix of gases in trimix are generally accepted to be a maximum partial pressure of oxygen (PO 2 —see Dalton's law) of 1.0 to 1.6 bar and maximum equivalent narcotic depth of 30 to 50 m (100 to 160 ft). At 100 m (330 ft), "12/52" has a PO 2 of 1.3 bar and an equivalent narcotic depth of 43 m (141 ft).
Medical use liquid oxygen airgas tanks are typically 2.4 MPa (350 psi). [citation needed] All equipment coming into contact with high pressure oxygen must be "oxygen clean" and "oxygen compatible", to reduce the risk of fire. [3] [4] "Oxygen clean" means the removal of any substance that could act as a source of ignition. "Oxygen compatible ...
Pressure in blanketed tanks is maintained by self actuating pressure control valves (PCVs). As liquid is withdrawn from the tank the pressure in the gas space falls. The blanket gas supply valve opens to maintain the pressure. As the tank fills with liquid the pressure rises and a vent gas valve open to vent gas to atmosphere or a vent system. [11]
This can be compensated by using a small sampling pump drawing gas from the blending tube and delivering it to the instruments, or by allowing for the reduced inlet pressure for oxygen analysis with an in-line sensor cell. This would require a vacuum gauge measuring the pressure drop or absolute pressure at the sensor.
Methods of oxygen storage for subsequent use span many approaches, including high pressures in oxygen tanks, cryogenics, oxygen-rich compounds and reaction mixtures, and chemical compounds that reversibly release oxygen upon heating or pressure change. O 2 is the second most important industrial gas.