Mercaptans, which are sulfur-containing compounds, are employed to impart a distinct odor akin to rotten eggs or cabbage to natural gas, n-butane, and propane. This distinctive smell serves as a vital warning sign for gas leaks. However, the odor of mercaptan can diminish for various reasons:

1. Absorption or oxidation occurs when leaked natural gas or propane from underground pipelines interacts with soil and concrete.

2. Materials like plasterboard and plywood can also contribute to the fading of the odor.

3. The installation of new piping for natural gas or storage tanks for propane can result in the odorant being adsorbed into the interior of the pipes or tank shell.

Given these potential odor fade scenarios, gas suppliers strongly advise that firefighting personnel utilize gas detection equipment to identify any leaks of natural gas or propane. This precaution ensures safety in situations where the odor may no longer serve as a reliable indicator of gas presence.