they way i had mine set up with out a controller worked pretty well,i basically built a ring with the supplied clear air tubing and hung it from the roof right above plant level that way the co2 fell directly onto my plants,i had my exhaust fan and my oscilating fans set to the exact time as my co2 timer,when the co2 came on the exhaust and fans went off,the only thing running was my intake.i did three 15 min bursts.as soon as the lights came on,middle of the cycle and about an hour before lights out.i have my lights vented with ther own fan,so even when the co2 was being released the lights stayed cool and kept the temps down in the room.believe it or not but running high pressure lamps can easily bump the temps up 30 degrees in 15 mins and tank at least a half our to recover to your normal room temp.