I use fans for every things in my cab: extraction, intraction, ventilation, but i dont use any ducting. PC fan dont give enough pressure to extract through a duct longer than 1-2ft.

I made my own carbon filters. I have one attached to one 12cm fan extracting, but the filter low largely the flow from the fan. I needed to put an aditional fan extracting (i use 220w of CFLs).

But you can made a carbon filter and put it out the cab, with a fan. As larger the carbon surface and thickness, larger the odor absortion. And as slower the air passes throught the carbon, the larger odor absortion. It wont work as well as a carbon filter in the extraction, but reduces smell a lot.
knna Reviewed by knna on . my idea for odor control... ok so ventilation/odor control, ive been doing some brainstorming... I think im going to buy a computer fan... and connect a 3 in hose from the exhaust of the fan to a hole in my cabinet. That should successfuly suck alot of heat out and expell it into my room. Only prob is when the plant is flowering my room is gonna reek. So im going to sharper image and buying one of those desk size Ionic Breeze (~50$) and stick it inside. Plus, im gonna tape some dryer sheets up to the hole so the Rating: 5