Liquefied petroleum gas (LPG) is a colourless odourless liquid which readily evaporates into a gas. Normally an odourant has been added to it to help detect leaks. LPG (either Butane or Propane), is generally stored and distributed as a liquid and it is widely used for process and space heating, cooking and automotive propulsion. It is classified as highly flammable and if it contains more than 0.1%Butadiene, it is also classified as a carcinogen and mutagen.
As pure LPG is odourless and invisible, a distinctive garlic-like odour is usually added to warn of its presence thus enabling easier detection. Ethyl mercaptan, C2H5SH, also referred to as ethanethiol, is usually added to give it that characteristic odour to make it easier to detect. It is a colourless organic liquid that has a strong odour and is added to odourless fuel and fuel systems as a warning agent.
The hazards commonly associated with LPG are fire and explosion. This derives from its inherent characteristic of high flammability and in extreme cases may combine with high pressure, and lead to a phenomenon known as the Boiling Liquid Expanding Vapour Explosion (BLEVE) phenomenon. This type of explosion occurs when a vessel containing a pressurised liquid is ruptured due to high temperature and pressure. Such explosions can be extremely hazardous. LPG may leak as a gas or a liquid. If the liquid leaks it will quickly evaporate and form a relatively large cloud of gas which will drop to the ground, as it is heavier than air. LPG vapours can run for long distances along the ground and can collect in drains or basements. When the gas meets a source of ignition it can burn or explode.
It is also important to note that cylinders can explode if involved in a fire, and most of all, can cause cold burns to the skin especially to those gas attendants who refill cylinders without proper protective clothing.