LPG is an odourless and colourless combustible substance that is a gas at normal pressure but liquid at higher pressures. Odorants are added to LPG to make it possible to detect leaks. It is important to remember that LPG is half as dense as water in its liquid form and twice as dense as air in its gaseous state. Thus water will collect below the LPG in the storage tank and when in the form of a gas, it will settle in lower places.
In normal conditions, LPG is essentially boiling and thus constantly giving off additional combustible gas. To ignite, a specific mixture of air and gas is required, around 2-10 per cent gas in air. The temperature of the ignition source must be at least 410 °C.
Clean combustion of LPG produces CO2 and H2O – carbon dioxide and water vapour, which are both present in nature. The combustion process also gives off heat, which is usually the main goal.
The density of LPG depends greatly on the ambient temperature. Thus at +20 °C propane can weigh 0.50 kg/l and at -20 °C butane weighs 0.64 kg/l. Thus liquefied gas is only sold by weight. This makes it easier to calculate the calorific value: 12.8 kWh/kg.
Often customers confuse natural gas (methane) and LPG (propane, butane). The most important is to realize that natural gas is lighter than air and tends to escape upward.
LPG consists of two primary components: propane and butane. These two hydrocarbons have much in common but also a few differences. Propane, with a molecular formula of C3H8, boils at -42 °C and butane, C4H10, has a boiling point of -1 °C.