iGS-221 CO2/RH/Temp Smart ControllerOne simple controller to manage ALL of your indoor garden's climate parameters! The iGS 221 can operate the intake and exhaust fans cyclically to replenish the garden's atmosphere in oxygen as it is needed for the plants and for safe CO2 combustion generator operation. When a CO2 combustion generator (propane or natural gas) is used to raise the CO2 level, ventilation for at least 2 to 5 minutes is mandatory to replenish the oxygen supply required by