What odorant is commonly added to natural gas and propane?

Mercaptan is the odorant commonly added to natural gas and propane to provide a distinct smell that helps in the detection of gas leaks. This compound, which has a strong, sulfur-like odor often described as resembling rotten eggs, is crucial for safety purposes. Natural gas and propane are both colorless and odorless in their natural state, making it impossible to detect a leak without an added odorant. By incorporating mercaptan, the presence of gas can be easily identified, enabling prompt action to prevent accidents or hazards associated with gas accumulation. This safety measure is a critical part of gas distribution systems to ensure that leaks can be detected early, reducing the risk of explosions or asphyxiation. Other substances listed, such as ethylene, octane, and chlorine, do not serve the same purpose and are not used as odorants for these fuels.