Overview: 

 Natural gas is a general term for a mixture of hydrocarbon-based gas that exists in underground rock reservoirs, with a specific gravity of about 0.65, lighter than air, and has colorless, tasteless and non-toxic properties. Natural gas is mainly composed of alkanes, of which methane accounts for the majority, as well as a small amount of ethane, propane and butane, in addition to hydrogen sulfide, carbon dioxide, nitrogen and water vapor, and a small amount of carbon oxide and trace amounts of rare gases, such as hene and argon. Before natural gas is delivered to end users, in order to help detect leaks, thiols, etc. are also used to add odors to natural gas.