Hey Gnome, Hey SC, I figure it is me you are wondering about with the 2 filters?

The reason I have the 8 inch in there is to scrub the room odor continuously. I also use the 8 inch inline fan as a Co2 delivery system and to recirc new air through the garden. I mount the duct along the corner at the deiling. I seal the end with aluminium tape. I cut holes in the duct to allow air and Co2 to exhaust right onto the plants. The carbon filter is on the ground and in front of the A/C. It pics up the Co2 and cool air and drops it directly onto the garden.

The second filter is there to combat the humidity spike that occurs when the lights go out. That filter comes on, the dehumidifier fires up, and the Co2 stops dispensing at lights out. The fan exhausts into the attic. Probably not so important now but when I have buds they wont be getting moldy!!
I also plan to get a controller that will allow me to set that exhaust filter so it can be used as a high temp safety valve of sorts. I will have it come on if the air gets 95+.

I hope it all make sense. -Jay

Peace and Love.

PS. please take a look at my post in the hydro topics..."2000w to 3000w Should I expand or thin out crop?"