This is a link on how to make a pretty cheap and easy carbon scrubber. Haven't made one myself, but the general idea is all you need and you can make one custom for your application. I'm going to try and scale this down, make it 4" outer diam 2" inner and pull air through it with a pc fan I have. My box is only 2X1X3
http://boards.cannabis.com/growroom-...on-filter.html