Liquefied petroleum gas (also called LPG, GPL, LP Gas, autogas, or liquid propane gas) is a flammable mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles. It is increasingly used as an aerosol propellant and a refrigerant, replacing chlorofluorocarbons in an effort to reduce damage to the ozone layer.
Varieties of LPG bought and sold include mixes that are primarily propane (C3H8), primarily butane (C4H10) and, most commonly, mixes including both propane and butane, depending on the season — in winter more propane, in summer more butane. Propylene and butylenes are usually also present in small concentration. A powerful odorant, ethanethiol, is added so that leaks can be detected easily. The international standard is EN 589. In the United States, thiophene or amyl mercaptan are also approved odorants