The term “liquefied gas” may seem a contradiction in terms since all things in nature are either a liquid or a solid or a gas. Yet, liquidity is the unique character of LPG that makes it such a popular and widely used fuel. At normal temperature and pressure, LPG is gaseous. It changes to a liquid when subjected to modest pressure or cooling. In liquid form the tank pressure is about twice the pressure in a normal truck tyre, which means it is very safe when properly handled. LPG is a derivative of two large energy industries: the processing of natural gas liquids and the refining of crude oil.