Under what condition can mercaptan odors be undetectable?

The ability to detect mercaptan odors, which are added to normally odorless natural gas as a safety measure, can be compromised when other stronger odors are present. This phenomenon occurs because the human olfactory system can become overwhelmed or desensitized by more potent smells, making it difficult to identify the specific scent of mercaptan.

For instance, in a busy kitchen filled with smells from cooking, or in areas where industrial processes are underway, the presence of these stronger odors can mask the mercaptan, leading to a failure to notice a potentially dangerous gas leak. This emphasizes the importance of being in an environment with minimal competing aromas when trying to detect gas leaks for safety purposes.

The other conditions listed, while they may influence the general perception of odors, do not specifically impact the detectability of mercaptan in the same direct way as competing smells do.