Hey how ya doing i have just purchased a 20 lb co2 cylinder and a regulator for my grow I have a 250 watt mh/hps light im using a make shift exhaust fan made out of 3 computer fans and some cardboard and a peice of duct work sucks prety well too i have another small 12 inch box fan sitting in the room is 9 ft tall 2 feet wide and 41/2 feet long just to give a quick description of wat i have to work with its not to much i am having touble setting up the co2 cylinder i cant figure out wat to set the timers and the fans at so i dont suck out too much c02 but still keep it cool enough for the plants