The Kronus 2 controls temperature, humidity, and CO2 in your grow area at your preferred settings. The Kronus 2 activates fans and A/C units to control temperature, or activates dehumidifiers to control humidity. Simply plug in your fan, dehumidifier, or A/C into the "Exhaust Fan Output" to control your temperature or humidity, and plug your CO2 equipment into the "CO2 Output" to keep your grow room environment in check. The Kronus 2 has a built in photo sensor to only activate CO2 during the daylight periods. The Kronus 2 does not read CO2 levels; it simply turns on/off CO2 equipment.