Raw natural gas is odorless, so a distinctive odorant that smells very much like strong sulfur is added prior to distribution. This strong odor makes the presence of a leak very easy to detect. If an odor is detected, please inspect the vehicle for the source of the concern and repair as needed. When you first smell the odorant, the concentration is approximately at 1% by volume. However, the odorant does not get stronger as the concentration increases. That means if you smell the odorant, you are at least at a 1% concentration level.