Lambda and excess air in natural gas combustion: what they mean

Lambda is a key metric in combustion control, indicating how much air we provide relative to the theoretically required amount.

Lambda = 1

Theoretically corresponds to the stoichiometric amount of air. In practice, burners usually operate with some excess air.

Lambda greater than 1

Means there is more air than theoretically required.

Very large lambda

Can reduce efficiency because excess air is heated and discharged through the flue.

Very small lambda

Can increase CO and create unstable or unsafe combustion.