(2) Liquefied petroleum gas or liquid petroleum gas (LPG or LP gas), 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. Chemically, LPG is a mixture of two flammable but nontoxic gases called propane and butane. Both of these are hydrocarbons (their molecules are made from different combinations of hydrogen and carbon atoms).