G2 Gas Fitter Practice Exam

The addition of an odorant to natural gas is crucial for safety because natural gas is colorless and odorless in its pure state, making it difficult for individuals to detect leaks without an added scent. Mercaptan is the substance most commonly used as the odorant in natural gas. It has a distinct, strong smell often compared to rotten eggs or skunk, which allows for easy identification even at very low concentrations. This characteristic helps ensure prompt action in case of a gas leak, significantly reducing the risk of dangerous situations such as explosions and asphyxiation.

The other options, while they may have their own uses in different contexts, do not provide the same effectiveness or recognition for leak detection as mercaptan does. For example, propane and butane are both gases themselves and are typically associated with fuel sources rather than added for detection, while ethanol is not used as a gas odorant and doesn't have the same properties conducive to leak detection.