LPG

Liquefied petroleum gas (also called LPG, LP Gas, or autogas) is a fusion of hydrocarbon gases used as a fuel in heating appliances and vehicles, and increasingly replacing chlorofluorocarbons as an vaporizer propellant and a refrigerant to decrease damage to the ozone layer.

Varieties of LPG bought and sold include mixes that are primarily propane, mixes that are primarily butane, and the more common, mixes including both propane (60%) and butane (40%), 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.

LPG is manufactured during the refinement of crude oil, or extracted from oil or gas streams as they materialize from the ground. At normal temperatures and pressures, LPG will vanish. Because of this, LPG is supplied in pressurised steel bottles. In order to allow for thermal extension of the contained liquid, these bottles are not filled completely. Typically, they are filled to between 80% and 85% of their capacity. The share between the volumes of the vaporised gas and the liquefied gas varies depending on composition, pressure and temperature, but is typically around 250:1. The pressure at which LPG becomes liquid, called its vapor pressure, similarly varies depending on composition and temperature; for example, it is approximately 220 kilopascals (2.2 bar) for pure butane at 20 °C (68 °F), and approximately 2.2 megapascals (22 bar) for pure propane at 55 °C (131 °F). LPG is heavier than air, and thus will flow along floors and tend to settle in low spots, such as basements.