Butane and propane

Butane and propane, odorless, colorless, flammable gases. These hydrocarbons (compounds of hydrogen and carbon) are found in natural gas and crude petroleum, and can be produced by cracking, a chemical process by which gasoline is derived from heavy oil. In their liquid form (referred to as LPG, or liquified petroleum gas), they are used as fuels for industry and for isolated homes.