When adjusting an oil burner, why do we allow for excess air?

Allowing for excess air when adjusting an oil burner primarily serves safety reasons. An excess of combustion air ensures that there is enough oxygen available for the complete combustion of the fuel. This is critical because insufficient air can lead to incomplete combustion, which can produce carbon monoxide and other harmful byproducts. By maintaining a controlled excess of air, the burner operates more safely, reducing the risk of producing dangerous emissions.

While factors like fuel efficiency, burner lifespan, and accommodating seasonal changes may have some relevance in the context of burner operation, they do not capture the primary reason for allowing excess air. Safety remains the most pressing concern, as ensuring complete combustion protects both the equipment and the occupants of the space where the burner operates.