SGP40 Air Quality Sensor SparkFun SGP40 Air Quality Sensor is designed to measure the quality of air in a limited enclosed space. The SGP40 is based on Sensirion's CMOSens® technology. It combines a metal oxide (MOx) sensor with a temperature-controlled micro hotplate to offer a humidity-compensated volatile organic compound (VOC) based indoor air quality signal. The sensing element and VOC Algorithm feature unmatched robustness against contaminating gases present in real-world applications. Additionally, this enables exceptional long-term stability and low drift with a device-to-device variation.