Combustion analysis is the process of measuring the byproducts of fuel combustion in gas furnaces, boilers, and water heaters to verify safe, efficient, and complete combustion. It is performed using a combustion analyzer inserted into the flue gas stream.
A combustion analyzer measures: flue gas temperature, oxygen (O2) percentage, carbon monoxide (CO) concentration, carbon dioxide (CO2) percentage, and calculates combustion efficiency and excess air percentage. Ideal combustion produces only CO2 and water vapor; incomplete combustion produces CO, which is toxic.
HVAC technicians should perform combustion analysis during every furnace or boiler tune-up. Dangerously high CO levels (above 100-400 ppm in the flue, depending on standards) require immediate action. Combustion problems can be caused by heat exchanger cracks, improper air-to-fuel ratio, dirty burners, or inadequate combustion air supply. Annual combustion analysis is as important for gas equipment as oil changes are for engines.