I have a room where we all hang out and smoke in, and it's a little hot in the room. Luckily this room was a 1 car garage converted into a room, so it has those little 14x6 square vents around the bottom of the walls. I purchased a 6" inline fan @ 250cfm, which should replace the air in this room every 8 minutes by my calculations. I have the fan attached to 6" duct tubing that is then connected to a 6" circular to 14"x6" square metal piece, which connects to the square vent to expel the air outside. I will be placing this setup closer to the ceiling, and run the ducting down to the square vent at the bottom of the wall.
I'd like to put this DIY carbon filter somewhere in the middle of this setup. With that said, could I modify these instructions and swap out the end caps with an 8"-6" reducer, and then wrap the middle section with metal sheeting and clamp the sheeting down with clamps? This way, all air would be passing through the ducting and going outside.
Would this still work efficiently, or would I need to get a more powerful fan?