Oxygen can be used medically for patients who require mechanical ventilation, often at concentrations above the 21% found in ambient air. Treatments are flexible enough to be used in hospitals, the patient’s home, or increasingly by portable devices. Oxygen tents were once commonly used in oxygen supplementation, but have since been replaced mostly by the use of oxygen masks or nasal cannulas.
Oxygen, as a supposed mild euphoric, has a history of recreational use in oxygen bars and in sports. Oxygen bars are establishments, found in Japan, California, and Las Vegas, Nevada since the late 1990s that offer higher than normal O 2 exposure for a fee. Professional athletes, especially in American football, also sometimes go off field between plays to wear oxygen masks in order to get a “boost” in performance. The pharmacological effect is doubtful; a placebo effect is a more likely explanation. Available studies support a performance boost from enriched O2 mixtures only if they are breathed during aerobic exercise.
Smelting of iron ore into steel consumes 55% of commercially produced oxygen. In this process, O2 is injected through a high-pressure lance into molten iron, which removes sulfur impurities and excess carbon as the respective oxides, SO2 and CO2. The reactions are exothermic, so the temperature increases to 1,700 °C.
Another 25% of commercially produced oxygen is used by the chemical industry. Ethylene is reacted with O2 to create ethylene oxide, which, in turn, is converted into ethylene glycol; the primary feeder material used to manufacture a host of products, including antifreeze and polyester polymers (the precursors of many plastics and fabrics).
Most of the remaining 20% of commercially produced oxygen is used in medical applications, metal cutting and welding, as an oxidizer in rocket fuel, and in water treatment. Oxygen is used in oxyacetylene welding burning acetylene with O2 to produce a very hot flame. In this process, metal up to 60 cm thick is first heated with a small oxy-acetylene flame and then quickly cut by a large stream of O2. Larger rockets use liquid oxygen as their oxidizer, which is mixed and ignited with the fuel for propulsion.
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