your gonig 2 have 2 buy a co2 controler if you want it right, timers suck!! a co2 controler measures the co2 ppm with a sensor and turns on if you need it, i got a cd36 co2 gen and a sentinal controler, i keep my co2 set at 1200 ppm when my sensor reads that my ppm is low my cd36 kicks on and...