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The helium is included as a substitute for some of the nitrogen, to reduce the narcotic effect of the breathing gas at depth and to reduce the work of breathing. With a mixture of three gases it is possible to create mixes suitable for different depths or purposes by adjusting the proportions of each gas.
The mass of the helium is a small part of the total. and density of oxygen and nitrogen are fairly similar. A reasonable approximation is to use the volume at 20 °C, ignore the mass of helium and take all nitrox and air components to be 1.3 kg/m 3. Using these approximations the estimate for the previous example is:
Gas blending for scuba diving is the filling of diving cylinders with non-air breathing gases such as nitrox, trimix and heliox. Use of these gases is generally intended to improve overall safety of the planned dive, by reducing the risk of decompression sickness and/or nitrogen narcosis, and may improve ease of breathing.
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. Other mixtures of gases, or pure oxygen, are also used in breathing equipment and enclosed habitats such as scuba equipment, surface supplied diving equipment, recompression chambers, high-altitude mountaineering, high-flying aircraft, submarines ...
Analysing a trimix blend using a portable helium analyzer Two oxygen cells as used by oxygen anylysers for diving gas Oxygen and helium analyser for breathing gas for diving. Before a gas mix leaves the blending station and before the diver breathes from it, the fraction of oxygen in the mix should be checked.
Helium has a higher heat conductivity than nitrogen and oxygen, but has a lower specific heat, so heat loss to helium based breathing gases is less than to air or nitrox. [22] This heat loss to breathing gas compounds the risk of hypothermia already present in the cold temperatures usually found at greater depths.
Heliox is a breathing gas mixture of helium (He) and oxygen (O 2).It is used as a medical treatment for patients with difficulty breathing because this mixture generates less resistance than atmospheric air when passing through the airways of the lungs, and thus requires less effort by a patient to breathe in and out of the lungs.
Rebreather technology may be used where breathing gas supply is limited, such as underwater, in space, where the environment is toxic or hypoxic (as in firefighting), mine rescue, high-altitude operations, or where the breathing gas is specially enriched or contains expensive components, such as helium diluent or anaesthetic gases.