The SOX2 gives technicians accurate combustion testing, measuring flue gas %O2, temperature, and calculating %CO2 and % Excess Air. The SOX2 tests the three most common fuel types for residential and light commercial combustion equipment: Natural gas, Oil #2, and Propane. The SOX2 switches between natural gas, oil#2, and propane fuel types with the push of a button. The differentiation between fuel types provides a more accurate calculation of %CO2. The SOX2 measures percent oxygen (%O2) and stack temperature by inserting the included pump and ATBF1 high-temperature thermocouple into the flue. Then it calculates the resulting percent carbon dioxide (%CO2) and excess air (%EA) present during combustion. The SOX2 also comes with a small screwdriver for field calibration of the thermocouple, thermocouple clips, and our ANC1 carrying case.