you need a fan that will move large amounts of air fast. ratings for fans are CFM (cubic feet per minute). you want to exhaust your grow area at the minimum of every 5 minutes, perferribly every 1 or 2.

l x w x h will give you cubic feet. now find a fan that will move the appropriate amount of air. you can find a cheap "can fan" for ~$20-25 and they move up from there.

try that and see what happens.


-shake