G2 Gas Fitter Practice Exam

Which are the major constituents of flue gases after the proper combustion of natural gas in air?

1. N2, O2, CO, H2O

2. CO2, H2O, N2, O2, and heat

3. CO2, SO2, H2O, and particulates

4. O2, CO2, methane, and nitrogen

The correct answer is: CO2, H2O, N2, O2, and heat

The major constituents of flue gases produced from the proper combustion of natural gas in air primarily include carbon dioxide (CO2), water vapor (H2O), nitrogen (N2), oxygen (O2), and heat. During combustion, natural gas (which primarily consists of methane) reacts with oxygen from the air to produce these gases. When methane burns completely, it reacts with oxygen to form carbon dioxide and water. Nitrogen is also present in the air and serves as an inert gas in the combustion process. Although some residual oxygen may be present, particularly if combustion is not perfectly balanced, the main byproducts of complete combustion are CO2 and H2O. The heat generated during this reaction is also a significant component of the flue gases, as it is the energy released during combustion. This understanding is crucial for gas fitters as it relates to combustion efficiency and emissions monitoring. Proper combustion minimizes harmful emissions and maximizes energy output, which is key in the handling and installation of gas appliances.