filter??

hey guys just wanted some input. im putting up an enclosed 25 square foot growing space, i'll have about 22 plants in that under most likely a 1000w hps (or 430 for now)
ive had problems designing the exhaust and dont know how big a filter and fan i will need. also, am i going to need an intake fan or will a passive vent do the trick (how big, and the odor wont escape through it, right?)

any help would be much appreciated.
cheers,

Well...welcome Lady, don't forget our ladies. Soo.. 25 sq ft, kinda like a 5' by5' area? what is the height? In order to figure the ize of your exhaust fan you need cubic feet (cfm). Multiply your height by the 25 sqft to get cubic feet. Your exhaust fan should have the capacity to remove that amount of air every few minutes(cfm). For intake, passive in take can be used, it will save energy. It should be twice as large as the exhaust ducting, ie 6" duct 12" passive intake. Filters are rated the same way, cfm. If your concerned about smell leaking out you could just get a 'carbon filter' commonly available at Menards, Lowes etc. I use one for my bud dryer. You can stand right next to it and not smell anything. Before you decide on lights you may want to check t-5's as well. VV