What are the main byproducts of combustion?

The main byproducts of combustion in a fuel-burning process, particularly in the context of natural gas, are carbon dioxide (CO2), water (H2O), and heat. During combustion, hydrocarbons react with oxygen, resulting in a chemical reaction that primarily produces these three substances.

Carbon dioxide is a complete combustion product emitted when carbon in the fuel combines with oxygen. Water is created when hydrogen in the fuel reacts with oxygen. The heat generated is a result of the exothermic nature of the combustion reaction, providing energy. While carbon monoxide (CO) can occur during incomplete combustion, it is not a primary byproduct when combustion is complete, hence the mention of "trace amounts" indicates that its presence is not typical in a properly functioning system.

The other options include various combinations of byproducts, but they do not accurately capture the complete combustion reaction as comprehensively as option C does. This understanding is crucial for HVACR professionals, as it guides them in assessing combustion efficiency and safety in heating applications.