In the whole process of the boiler or other burner, fuel and combustion air are added to the combustion chamber from the beginning stage, and then the actual combustion is carried out until the flue gas cleaning and the final emission test. By measuring the concentration of O2, CO, CO2 (or NOx/NO, NO2, SO2, CH4) in the combustion process, our flue gas analyzer calculates combustion efficiency, excess air coefficient and other parameters to regulate combustion equipment to the best combustion condition.