Oxygen is routinely, but not always vented to the atmosphere. Because oxygen can be separated from air at relatively low cost, economics generally dictates that it be vented. Where there are local uses of oxygen such as in wastewater treatment, it may have an industrial use. Electrolyzers are used in submarines and spacecraft to supply breathable oxygen.
One future use that may have significant value in decarbonizing the industrial and power sectors is oxy-fuel combustion—burning combustible fuels in pure oxygen rather than air. Because air consist of 78% nitrogen and 21% oxygen, oxy-fuel combustion dramatically reduces exhaust flow and increases the concentration of combustion products, facilitating capture an reuse of combustion products (e.g., carbon dioxide for carbon sequestration or carbon monoxide for alkane synthesis). It also prevents the formation of nitrogen oxides, which is the major potential air pollutant from the combustion of hydrogen.