An air quality sensor is a device used to detect the concentration of pollutants in the air. It can usually measure two or more air quality indicators, such as temperature, humidity, carbon dioxide, carbon monoxide, ozone, formaldehyde, benzene, PM2.5, PM10, etc. It is an important part of the air purifier and fresh air system. Further, the air quality sensor's working principle is to detect gas and particulate matter indicators in the air through optical, electrical, thermal, and other methods.