When oxygen is plentiful, butane burns to form carbon dioxide and water vapor; when oxygen is limited, carbon (soot) or carbon monoxide may also be formed. Butane is denser than air.
Normal butane can be used for gasoline blending, as a fuel gas, fragrance extraction solvent, either alone or in a mixture with propane, and as a feedstock for the manufacture of ethylene and butadiene, a key ingredient of synthetic rubber. Isobutane is primarily used by refineries to enhance (increase) the octane number of motor gasoline.
When blended with propane and other hydrocarbons, it may be referred to commercially as LPG, for liquefied petroleum gas. It is used as a petrol component, as a feedstock for the production of base petrochemicals in steam cracking, as fuel for cigarette lighters and as a propellant in aerosol sprays such as deodorants.
Very pure forms of butane, especially isobutane, can be used as refrigerants and have largely replaced the ozone-layer-depleting halomethanes, for instance in household refrigerators and freezers. The system operating pressure for butane is lower than for the halomethanes, such as R-12, so R-12 systems such as in automotive air conditioning systems, when converted to pure butane will not function optimally and therefore a mix of isobutane and propane is used to give cooling system performance comparable to R-12.
Butane is also used as lighter fuel for a common lighter or butane torch and is sold bottled as a fuel for cooking, barbecues and camping stoves. Butane canisters global market is dominated by South Korean manufacturers.
As fuel, it is often mixed with small amounts of hydrogen sulfide and mercaptans which will give the unburned gas an offensive smell easily detected by the human nose. In this way, butane leaks can easily be identified. While hydrogen sulfide and mercaptans are toxic, they are present in levels so low that suffocation and fire hazard by the butane becomes a concern far before toxicity. Most commercially available butane also contains a certain amount of contaminant oil which can be removed through filtration but which will otherwise leave a deposit at the point of ignition and may eventually block the uniform flow of gas. Contaminants are not used in fragrance extraction and butane gases can cause gas explosions in poorly ventilated areas if leaks go unnoticed and are ignited by spark or flame.