Description
Liquefied petroleum gas or liquid petroleum gas
(LPG ) also referred to as simply propane or butane, are flammable
mixtures of hydrocarbon gases used as fuel in heating appliances,
cooking equipment, and vehicles. It is increasingly used as an
aerosol propellant and a refrigerant[citation needed], replacing
chlorofluorocarbons in an effort to reduce damage to the ozone
layer. When specifically used as a vehicle fuel it is often
referred to as autogas.
LPG is prepared by refining petroleum or "wet" natural gas, and is
almost entirely derived from fossil fuel sources, being
manufactured during the refining of petroleum (crude oil), or
extracted from petroleum or natural gas streams as they emerge from
the ground. As its boiling point is below room temperature, LPG
will evaporate quickly at normal temperatures and pressures and is
usually supplied in pressurised steel vessels. They are typically
filled to ***5% of their capacity to allow for thermal expansion of
the contained liquid. The ratio between the volumes of the
vaporized gas and the liquefied gas varies depending on
composition, pressure, and temperature, but is typically around
**0:1. The pressure at which LPG becomes liquid, called its vapour
pressure, likewise varies depending on composition and temperature;
for example, it is approximately **0 kilopascals (*2 psi) for pure
butane at *0 °C (*8 °F), and approximately 2,**0 kilopascals (**0
psi) for pure propane at *5 °C (**1 °F). LPG is heavier than air,
unlike natural gas, and thus will flow along floors and tend to
settle in low spots, such as basements. There are two main dangers
from this. The first is a possible explosion if the mixture of LPG
and air is within the explosive limits and there is an ignition
source. The second is suffocation due to LPG displacing air,
causing a decrease in oxygen concentration.