Technical Standards and Safety Authority (TSSA) G3 Practice Exam

What component is essential in the flue gas of a complete combustion process?

1. Carbon monoxide

2. Hydrogen

3. Water vapor

4. Aldehydes

The correct answer is: Water vapor

In a complete combustion process, the primary products are typically carbon dioxide, water vapor, and energy. The presence of water vapor is essential as it indicates that hydrogen from the fuel has reacted with oxygen during combustion to form H2O. In contrast, the other options represent incomplete combustion products or are not typically seen in a complete combustion scenario. Carbon monoxide occurs when there is insufficient oxygen, leading to incomplete combustion. Hydrogen may be present in the fuel but is not a direct product of combustion; it is used in the reaction to form water. Aldehydes are organic compounds that can be produced from incomplete combustion or from the breakdown of larger organic molecules, which again suggests a lack of complete combustion. Therefore, water vapor is a definitive indicator of a complete combustion process, fulfilling the criteria for a complete reaction where all available fuels are fully utilized, producing energy, carbon dioxide, and water vapor.