[header] How to tell if you have fixed a gas leak [title] Notice if you smell gas. [step] The smell of gas is one of the best indications that you haven't successfully fixed a gas leak. While you might not always be able to smell a leak, you should pay attention to see if you do notice the smell of leaking gas. 
[substeps] Gas smells like sulphur or " rotten eggs. " the smell of gas is made by mercaptan, an additive that is intended to help humans smell it.