for that small of a grow box, one CFL odor-killer should be plenty, ... I have two in a 2'x4'x7' cabinet, and they handle it fine, ... however, when the lights are off, so is the odor-killer CFL, so you would have to put the ionizer in the same room, but outside of your cabinet, ... not sure how well they work on the whole room (although their product description DOES mention entire rooms) ... wish I could tell you for sure ... :smokin: