What is an indication of a propane gas leak?

The presence of a propane gas leak is strongly indicated by the smell of rotten eggs. Propane itself is non-toxic, colorless, and odorless; therefore, to enhance safety and detection, an odorant called ethyl mercaptan is added to it. Ethyl mercaptan has a distinct, strong odor reminiscent of rotten eggs, making it much easier for people to recognize leaks early and take appropriate safety measures.

The other options do not accurately represent the smell associated with propane. For instance, while vanilla and a sweet smell may be pleasant, they do not correspond to the added odorant for safety in propane. Similarly, indicating that propane has no odor is misleading, as the deliberate addition of the odorant aims to prevent dangerous situations by ensuring that any leakage is easily detectable. This makes the recognition of that specific rotten egg smell crucial for safety when handling propane.