Propane is produced from both natural gas processing and crude oil refining.
It is nontoxic, colorless and virtually odorless. As with natural gas, an identifying odor is added so the gas can be readily detected. Propane has a narrow range of flammability when compared with other petroleum products. If the mixture contains less than 2.2 percent gas, it is too lean to burn. If it contains more than 9.6 percent, it is too rich to burn.