LPG – Properties and Hazards

Properties

LPG is liquefied petroleum gas and is:

• Obtained during the processing of crude oil, or direct from the North Sea.
• Colourless and odourless. An odourising agent is added before distribution to give its characteristic smell.
• Half as heavy as water when in liquid form. It will float on water before vapourising.
• Easily liquefied by pressure, taking up only around 1/250th of its gaseous volume. This means that a large amount of LPG can be stored in a small place.
• Either commercial butane or commercial propane. These are similar in use but propane has a lower boiling point and hence a higher storage pressure. Commercial propane is predominantly an outdoor fuel, commercial butane is predominantly an indoor fuel.

At normal temperature (i.e.15 degrees Celsius), propane and butane cylinders are found at the following pressures:

Commercial BUTANE
2BAR (28psig)

Commercial PROPANE
7BAR(100psig)

Hazards

LPG:

• LPG is approximately twice as heavy as air when in gas form and will tend to sink to the lowest possible level and may accumulate in cellars, pits, drains etc.
• LPG in liquid form can cause severe cold burns to the skin owing to its rapid vapourisation.
• Vapourisation can cool equipment so that it may be cold enough to cause cold burns.
• LPG forms a flammable mixture with air in concentrations of between 2% and 10%.
• It can, therefore, be a fire and explosion hazard if stored or used incorrectly.
• Vapour/air mixtures arising from leakages may be ignited some distance from the point of escape and the flame can travel back to the source of the leak.
• At very high concentrations when mixed with air, vapour is an anaesthetic and subsequently an asphyxiant by diluting the available oxygen.
• A vessel that has contained LPG is nominally empty but may still contain LPG vapour and be potentially dangerous. Therefore treat all LPG vessels as if they were full.