People who need the absolute best CO2 controller available today, use the PPM-2a from C.A.P. What sets the PPM-2a apart from the competition? Fuzzy Logic... Fuzzy Logic can be compared to a good driver. As a good driver approaches a red light, he or she applies the brakes to gradually slow down BEFORE getting to the intersection. Fuzzy Logic(tm) uses the same idea to bring the CO2 level up to the desired setting without over-shooting the desired CO2 level. The PPM-2a automatically dials-in the exact parameters for your area. It learns how your grow area uses CO2 and adapts to keep the CO2 levels constant. The PPM-2a can be connected to a temperature or environmental controller, disabling the CO2 function while your exhaust fans are running to reduce CO2 waste. The PPM-2a is capable of being used to control both compressed CO2 and gas-burning CO2 generators. When used with a CO2 generator, the user can change the PPM-2a mode to ON / OFF control which eliminates the rapid cycling of the CO2 generator. The PPM-2a will control any make of CO2 valve or generator that is 120 volts.