K here a pic of my fan , see the ducting behind it? thats thats my intake i have that attached to a 4" fan in the loft , i lifted a tile and put the fan directly under it ! so the fan will send the cool air all around the tent , you must have your outgoing air going directly out side , no good having it pumped in the room the room air will get to warm !! Attachment 276120 and that will be the same fan your useing for your carbon filter !!