The UEi C155 Combustion Analyzer is a no nonsense analyzer that gets the job done. This analyzer can measure temperature (20-2400 F), CO2 (0-20%), CO (0-2,000ppm). The C155 uses a CO2 sensor and the CO measurements to calculate the O2 present which increases the shelf life of the sensors. This change eliminates the need for the O2 sensor which in turns eliminates your need to send it in for replacement every year.