What type of air is mixed with gas before it reaches the burner port?

The correct choice is primary air, as it refers specifically to the air that is mixed with gas before it reaches the burner port. Primary air is essential in the combustion process because it allows for the proper mixing of fuel and air, ensuring efficient and complete combustion.

The amount of primary air must be carefully controlled to achieve the correct air-to-fuel ratio, which is critical for optimal burner performance. Too little primary air can result in incomplete combustion, leading to lower efficiency and increased emissions. Conversely, too much primary air can cool the flame and affect performance.

Secondary air, on the other hand, is introduced into the flame itself after the initial combustion has begun. It supports further combustion processes but does not mix with the gas prior to reaching the burner.

Excess air refers to the additional air provided beyond what is needed for complete combustion. While this can help ensure that all the fuel is burned, it is not mixed with the gas before reaching the burner port.

Combustion air is a broader term that generally describes the air required for the combustion process, including both primary and secondary air, but does not specifically denote the air mixed with the gas prior to combustion. Therefore, it is the primary air that specifically denotes the air mixed with the