You want an NDIR CO2 sensor such as an SCD30 or a T6713 and not an electrochemical sensor. Electrochemical sensors respond to CO2 and other VOC gases and give

You want an NDIR CO2 sensor such as an SCD30 or a T6713 and not an electrochemical sensor. Electrochemical sensors respond to CO2 and other VOC gases and give you an "eCO2" reading, and you can never be really sure if it measured CO2 or something else, and require frequent calibration. They suck. NDIR CO2 sensors work by emitting IR light and measuring the CO2 by its IR absorption band, and are much more accurate at singling out only CO2 among other gases.