What substance is commonly added to natural gas to give it an odor?

Natural gas is naturally odorless, which poses significant safety risks in the event of a leak, as it would be difficult for individuals to detect escaping gas. To address this, a substance known as mercaptan is added to natural gas. Mercaptan has a distinct, strong odor often described as being similar to rotten eggs, which serves as an effective alert for leaks.

The addition of mercaptan allows individuals to detect even small amounts of gas, ensuring prompt action can be taken to address potential hazards. This practice is a crucial safety measure in the handling and distribution of natural gas.

Other substances listed, such as propane and butane, are not used for this purpose. Propane is a different type of gas used for heating and cooking, while butane is used primarily as a fuel or lighter fluid. "Smelly Gas" is not a specific substance and does not pertain to the actual additives used in natural gas. Hence, mercaptan remains the correct and widely recognized substance used for odorization of natural gas.