Natural gas is an odorless and colorless flammable gas. Natural gas odorization means operations involving addition of an odorant to gas to ensure characteristic odor of natural gas in order for people the odor to be distinctive and unpleasant so that the presence of gas in air in concentrations below the lower explosive limit (LEL) is readily detectable. By the odorant addition any physical or chemical property (except the smell) of natural gas cannot be changed. Generally speaking, in the process of natural gas delivering for both public and industrial use, odorization provides safety for those who use it.