This product uses MH-Z19C carbon dioxide gas sensor and AHT20 temperature and humidity sensor. MH-Z19C is a universal intelligent small sensor, which uses the principle of non-dispersive infrared (NDIR) to detect CO2 in the air. It has the characteristics of good selectivity, no oxygen dependence, long service life and built-in temperature compensation. The sensor is a high-performance sensor which combines the mature infrared absorption gas detection technology with the precise optical circuit design and excellent circuit design. AHT20 is equipped with a newly designed ASIC chip, an improved MEMS semiconductor capacitive humidity sensor and a standard on-chip temperature sensor. Its performance has been greatly improved and even exceeded the reliability level of the previous generation sensor. The new generation temperature and humidity sensor has been improved to make its performance more stable in harsh environment. Each sensor has been calibrated and tested, and is widely used in homes, hotels, offices and other places.