The model AOX2 Combustion Head measures %O2 and temperature of flue gases and can calculate the %CO2 found in the products of combustion. The AOX2 is designed to give you some basic information about the combustion process being analyzed. The AOX2 comes with clips for mounting the thermocouple to the end of the pump snoot, a water trap and filter with replacement filters to keep the sensor clean and free of moisture and a hand pump for manual aspiration of the sensor. Since %CO2 is calculated based on a known fuel, the %CO2 reading is only meaningful when testing combustion products of the selected fuel.