gee whiz, what size room? how many watts of light? What are you temps in the room? Lights on fan off? air cooled lights? put the fan on a controller, run you filter by itself, in the room, exhaust in the room. When your fan exhaust controller kicks on due to heat, it will exhaust filtered air. You can get by with the filter setup on the room exhaust but fan size is critical. You don't want to pull air across the carbon too fast. I have found that in room filter, separate from exhaust, works great. You can run a really large can with a smaller fan,since it runs 24/7. You can maintain higher room heat temps with C02. Growers need a controller when utilizing Co2. If air cooled lights, make sure your pulling air from outside the room,through the lights, exhaust out of the room,seal the joints with metal duct tape. Balance is the key. saves you money on electric, and wasted Co2. Co2 is worth it if the balance is achieved.