i use motors to vent out the fumes. if you decide to do the same be absolutely sure that they are "Brushless" motors. otherwise you will get a big bang out of the whole situation. quite litterally. brush dc motors will spark on occasion which could ignite the fumes.
All the filter is inteded to do is to prevent the paint itself from going into the duct work. and if you have motors in there it will ruin them.
i have done a bunch of research on this kind of thing. when i first decided to airbrush, which wasn't that long ago, i wanted an booth however they are a little expensive, so i made a cheap one out of a cardboard box, some wire, and a few T-pins. i use three brushless motors that are in a window to vent out the fumes. My dad had already built the motor mount and put the motors in when he was working on an entertainment center for our neighbors. that was so he could vent the lacquer and the lacquer thinner out so the rest of the family would asphyxiate
Jeffrey
Darth Vader says "Come to the dark side we have cookies!!!"