G2 Gas Fitter Practice Exam

Which gas is typically associated with combustion products in gas appliances?

1. Carbon dioxide

2. Oxygen

3. Hydrogen

4. Nitrogen

The correct answer is: Carbon dioxide

The presence of carbon dioxide in combustion products is a fundamental aspect of how gas appliances operate. When a gas appliance burns natural gas or another hydrocarbon fuel, the primary chemical reaction involves the gas combining with oxygen from the air. This combustion process yields energy in the form of heat, and carbon dioxide is one of the main by-products generated along with water vapor. In residential and commercial contexts, gas appliances such as furnaces, water heaters, and ovens predominantly produce carbon dioxide when functioning correctly. Monitoring the levels of this gas is crucial because, although it is not toxic at low levels, high concentrations can indicate poor combustion, leading to safety concerns such as inadequate ventilation and the potential build-up of harmful gases. Oxygen, while essential for combustion, is consumed during the process and is not found in the combustion products. Similarly, hydrogen and nitrogen are either not products of this process or are only present in trace amounts, making them less relevant to the outputs expected from gas appliances. Understanding the role of carbon dioxide helps ensure that gas appliances are functioning safely and efficiently.