Most of the hobby spray booths have the shaded pole blower like Mike has posted. I used it in a homemade bench and it works great. As Mike said, explosion proof motors are cost prohibative for most people.
Use of acrylics will also cut down the risk.
Volatiles have a habit of finding ignition points. A friend years ago lost his eyebrows and facial hair as the fumes from the Acetone he was using crept down the stairs to the water heater and flashed. He was real lucky.
The best practice is to get the motor out of the air flow, which is what a shaded pole blower does. Putting a fan at the beginning is putting you between a possible ignition source and a possible fuel.
Here's the link that has been around here for a while and will give you tons of good info and a link to grainger for fans.
http://modelpaint.tripod.com/booth2.htm