A Pilot study of the accuracy of CO₂ sensors in commercial buildings

Carbon dioxide (CO₂) sensors are often deployed in commercial buildings to obtain CO₂ data that are used to automatically modulate rates of outdoor air supply. The goal is to keep ventilation rates at or above design requirements and to save energy by avoiding ventilation rates exceeding design requirements. However, there have been many anecdotal reports of poor CO₂ sensor performance in actual commercial building applications. This study evaluated the accuracy of 44 CO₂ sensors located in nine commercial buildings to determine if CO₂ sensor performance, in practice, is generally acceptable or problematic. CO₂ measurement errors varied widely and were sometimes hundreds of parts per million. Despite its small size, this study provides a strong indication that the accuracy of CO₂ sensors, as they are applied and maintained in commercial buildings, is frequently less than needed to measure typical values of maximum one-hour-average indoor-outdoor CO₂ concentration differences with less than a 20% error. Thus, we conclude that there is a need for more accurate CO₂ sensors and/or better sensor maintenance or calibration procedures.