In the combustion control system of the gas heat treatment furnace, the oxygen content is an important parameter for the adjustment of the air-fuel ratio, which is used to judge whether the air is excessive in the combustion process, that is, the level of oxygen content in the flue gas.

During manual adjustment, the oxygen content is only used as a reference value. During automatic operation, the oxygen content is an important parameter. It is used to judge the best value of the air-fuel ratio of the gas heat treatment furnace. Therefore, the oxygen content detection position is generally set in the initial section of the flue of the gas heat treatment furnace.