Propane, ethane, butane, and mixtures consisting mainly of these three compounds are the most common LPGs. Natural gas is a mixture of about 90 percent methane, about five percent propane and about five percent other gases. These exist as gases in underground reservoirs. These reservoirs also contain some liquids. NGLs come from gas processing plants.
Refineries use large quantities of LRGs and NGLs.
Like all fossil fuels, they are a non-renewable energy source. Although each is nontoxic and odorless, foul-smelling mercaptan is added so propane leaks can be easily detected. Because propane is heavier than air, it sinks to the ground and can make vapor clouds. These pools can explode if a spark or match is struck. These gases dissipate quickly, so there are hardly ever explosions of this kind.