My flower room is 8'6" x 5'6" with 3 x 1000w hps 8" vented hoods. And an exra 600w hps for the hell of it. I use a 900cfm phat filter to vent all of the exhaust, a custom made indusrial hepa filter for the fresh air. With all of the fans I move about 1600cfm so the air in the room is exchanged...