Methanethiol is added to pure gas before it reaches homes and gives fuel it is well-known "rotten egg" smell to help residence owners detect a fuel leak [2]. https://www.bruederli.com/?s=https%3A%2F%2Fwww.northwestu.edu%2F%3FURL%3Dhttps%3A%2F%2Flondoncommercialgasengineer.com%2Findex.html