The NEW Novo 4N Portable Combustion Analyzer Oxygen (O2), Carbon Monoxide (CO), Nitric Oxide (NO), Nitrogen Dioxide (NO2, Nitrogen Oxide (NOx) and calcualtes Carbon Dioxide (CO2), along with all of the necessary temperature, draft, and pressure measurements for combustion efficiency analysis. The Novo 4S is a robust, reliable, precise instrument. ideal for HVAC Professionals.