Which odorant is added to propane to aid leak detection?

• A. Methyl mercaptan
• B. Butanethiol
• C. Ethyl mercaptanoxide
• D. Ethyl mercaptan

Answer: (D)

Gas is odorized because propane itself has no smell, so a detectable odor is added to help you notice leaks quickly. Ethyl mercaptan is chosen for this purpose because it produces a strong, distinctive sulfur-like odor even at extremely low concentrations, making leaks obvious long before amounts become dangerous. It also mixes well with propane and remains stable in the distribution system, so the scent is reliable and long-lasting enough to be noticed. Other listed sulfur compounds can have odors too, but ethyl mercaptan provides the right balance of detectability and compatibility for propane. An odorant that isn’t a real or standard addition to propane (such as an erroneous or non-viable compound) wouldn’t serve reliably for leak detection.