There are two basic types of LPG. Butane is commonly used as lighter, heater or camping stove fuel and in recent times as a propellant for aerosol cans of paint, hair spray, fly spray and so on. Propane is the gas used for road fuel as its calorific value (how much heat a given amount of gas measured by weight will produce when burned) is significantly higher than that of Butane.

LPG has one unique and very special property. If mildly compressed it easily changes to a liquid state. This allows a large amount of gas (stored energy) to be contained in a relatively small space. The reverse process is just as fortunate - If decompressed or escapes the tank the liquid gas will quickly revert to its gaseous state (vaporise).