Not sure if there is thread about this subject but i would like some input. I flower in a closet that is 3x6.5x8. I have a 6" x 24" carbon filter covered by a prefilter that is ducted to a roof vent. My son was on the roof working yesterday and he said the smell was very strong. I have 430 cubic foot fan in front of the filter. To try to keep the heat down some i have been running it wide open. I am guessing i am pulling the air thru the filter to quick. I guess that the only way to tell would be to have some one on the roof sniffing while you turn it down. Mostly posting for anyone that has to have stealth mode around your house.