High CO concentration is an indication of incomplete combustion and must be investigated immediately. It cannot be resolved solely by increasing air without checking the root cause.
Insufficient combustion air
Low air supply, clogged filters, or incorrect damper positioning can reduce available oxygen.
Poor air-fuel mixing
Issues with the burner head, nozzles, or flame geometry can cause a locally rich mixture.
Draft issues
Incorrect chimney draft or increased resistance at the flue gas outlet affects combustion stability.
Testing at different loads
CO must be checked at low, medium, and high fire, as the problem may only appear at a specific point on the curve.
Safety
High CO is a serious incident. Adjustment must be performed by a qualified technician using a flue gas analyzer and in accordance with the manufacturer's instructions.
