Is excess air considered combustion air?

Excess air refers to the additional air that is provided in a combustion process beyond what is necessary for complete combustion of the fuel. While combustion air is the air required to burn fuel efficiently, excess air can dilute the combustion process, which could lead to a lower combustion efficiency.

In combustion systems, the ideal operation occurs with just enough air to ensure complete combustion of the fuel. However, in practice, some systems add excess air to ensure complete combustion and to prevent the production of carbon monoxide and other harmful emissions. Nonetheless, this addition of air beyond what is strictly necessary for combustion is not considered part of the combustion air itself. Therefore, excess air is not classified as combustion air.

The distinction is important in HVAC and combustion analysis because using the right amount of combustion air is critical for system efficiency and safety. Too much excess air could lead to wasted energy and lower system performance. Thus, the correct understanding is that excess air is not considered combustion air.