Ethanethiol, which serves this purpose, is usually added to propane so leaks can be detected
If you wish to not have this information used for the purpose of serving you... [DOC] [TLE] The Smell of Danger - Bruce Goldfarb [PAR] propane leak and to prevent accidents, propane is odorized by mixing it ... 
enough odorant be added to propane so that it can be detected when it has 
reached one-fifth the ... amount.