LPG is composed primarily of propane (C3H8) and butane (C4H10), with smaller amounts of isobutane, propylene and butylene. The mixture is gaseous at room temperature and atmospheric pressure but converts to liquid under pressure, giving it a high energy density for transport and storage.

The addition of ethyl mercaptan gives otherwise odorless LPG a distinctive smell, a basic safeguard that helps users detect leaks before concentrations become dangerous.

Because LPG boils below room temperature, it evaporates rapidly at atmospheric pressure. It therefore must be held in specially engineered pressure vessels. These containers are built to withstand internal pressure and are equipped with pressure relief valves to respond to abnormal pressure increases caused by external heat.

LPG vapor is heavier than air. If a leak occurs, the gas tends to settle in low-lying areas such as basements, pits or drains, creating dual risks of explosion and asphyxiation. Adequate ventilation and routine inspections are central to safe operation.

LPG is used for home cooking, water heating, agricultural and industrial heating, and as a marine fuel. Its versatility has made it a common energy source in areas beyond the reach of natural gas pipelines.

In refrigeration, purified LPG mixtures such as R-290a are drawing attention as environmentally friendlier alternatives to traditional chlorofluorocarbon refrigerants because of their very low global warming potential.