The SAIR-1 4-in-1 sensor is the standard Environmental Sensor that is included with the SEN-1 / Sentry and GUARD-1 / Guardian controllers. The 4-in-1 Environmental sensor uses precision sensor elements to accurately measure Temperature, Humidity, CO2, VPD, CO2 (ppm). There is also a built-in photocell that is used to determine whether it is daytime or nighttime. All of the sensors used within the SAIR-1 have been selected for their high-accuracy and stability as well as their specific ability to resist abusive conditions normally present within growing spaces. Croptiva uses temperature and humidity sensor chips with the highest accuracy possible. They also feature a special protective layer to resist high humidity locations. *Included with the SEN-1 / GUARD-1.