LPG

LPG is a predominant mixture of propane and butane with a small percentage of unsaturates (propylene and butylene) and some lighter C₂ as well as heavier C₅ fractions. Included in the LPG range are propane (C₃H₈), propylene (C₃H₆), normal and iso-butane (C₄H₁₀) and butylene (C₄H₈). LPG may be defined as those hydrocarbons, which are gaseous at normal atmospheric pressure, but may be condensed to the liquid state at normal temperature by the application of moderate pressures. Although they are normally used as gases, they are stored and transported as liquids under pressure for convenience and ease of handling. Liquid LPG evaporates to produce about 250 times volume of gas.

LPG vapour is denser than air; butane is about twice as heavy as air and propane about one and a half time as heavy as air. Consequently, the vapour may flow along the ground and into drains sinking to the lowest level of the surroundings and be ignited at a considerable distance from the source of leakage. In still air, vapour will disperse slowly. Escape of even small quantities of the liquefied gas can give rise to large volumes of vapour/air mixture and thus cause considerable hazard. To aid in the detection of atmospheric leaks, all LPGs are required to be odorized. There should be adequate ground level ventilation where LPG is stored. For this very reason, LPG cylinders should not be stored in cellars or basements, which have no ventilation at ground level.