What is a common consequence of an improper air-to-fuel ratio?

An improper air-to-fuel ratio can lead to a flickering flame. This occurs because the combustion process is not achieving the optimal mixture of air and fuel. When there is too much fuel or not enough air, combustion becomes unstable, resulting in an inconsistent flame that can flicker. This flickering can indicate incomplete combustion, which not only affects the performance of the burner but can also lead to increased emissions and potential safety hazards.

In contrast, a balanced air-to-fuel ratio is crucial for maintaining stable combustion, improving efficiency, and ensuring that the burner operates smoothly. The other outcomes listed, such as increased efficiency, longer burner lifespan, and reduced noise levels, are typically associated with a correctly adjusted air-to-fuel ratio rather than the consequences of an improper one. Therefore, flickering flame serves as a clear indicator of combustion issues linked directly to the air-to-fuel mixture.