Combustion, breathing
Steel production
Water purification (ozone)
Component of sand, water, concrete...

Oxygen is mainly used in the metal-mechanic industries for welding and casting materials made iron and steel; it is also used in the production of synthesis gases, for oxidation of the natural gas and for reduction of the water vapor by the carbon. It is also used in the production of a great variety of substances of industrial interest, as the acetylene, the hydrogen peroxide (oxygenated water), the chlorine (for oxidation of HCl), the ethylene oxide, the ftalic anhydride, the ozone, etc. Less usual applications include the gas in bottles used by divers, in hyperbaric chambers for therapeutic purposes and in reaction motors.