Liquefied petroleum gas is a mixture of propane and butane, usually accompanied by a small amount of propylene and butene. Usually add a strong smell of ethanethiol, so that the leakage of LPG will be easily found. Liquefied petroleum gas is produced in the extraction of crude oil, or from the oil or natural gas exploitation process of gas emissions. Liquefied petroleum gas (LPG) is often mistaken for propane. In fact, LPG is a mixture of oil and natural gas at the appropriate pressure and is present at room temperature. In the United States and Canada, the mixing of these two substances is generally considered to be mainly composed of propane, while in many European countries the LPG has a propane content of only 50% or less.