What are the two most common fuel gases used within a structure?

The correct answer identifies natural gas and commercial propane as the two most common fuel gases used within a structure. Natural gas is primarily composed of methane and is widely used for heating, cooking, and providing hot water in residential and commercial settings due to its efficiency and widespread availability. It is delivered through pipelines directly into homes and buildings.

Commercial propane, on the other hand, is favored in areas where natural gas is not readily accessible. It is used in various applications such as cooking, heating, and powering some appliances. Both of these gases are combustible and produce energy when burned, making them essential for fulfilling the energy needs within structures.

In contrast, while propane and butane are related fuels, they do not represent the most common fuel gases used in structures as propane is more prevalent in the context of space heating and cooking. Methane and hydrogen do not accurately represent the typical fuel gas usage since hydrogen is not a prevalent fuel gas in residential settings at this time. Butane and nitrogen do not fit the context of common fuel gases used in structures, as nitrogen is an inert gas and not used as a fuel.