+1
In the electrical world (I work for a contractor) we try to avoid placing electrical devices (motors, switches, light fixtures etc.) within a hazardous-rated area whenever possible... less expensive installation and safer.
If you have access to a copy of the National Electrical Code, look up Article 516, Spray Application, Dipping, and Coating Processes:
If you have an enclosed booth, the space 3' from any opening is considered a Class I, Division 2 area (inside the booth itself is Class I Div 1). If you keep your fan motor and any other electrical devices out of this area, then they don't need to be hazardous location-rated (aka "explosion-proof"). The fan itself, though, should be rated for spray booth usage, i.e. non-ferrous, non-sparking blades, etc. Don't forget to ground any metallic surfaces within the booth and ductwork.
Have fun, and be safe
Mike
P.S. - if you are just converting a room into a spray booth, then that's another thing... you'd have to upgrade any existing switches, light fixtures, and wiring in the room to Class I Div 1. Not for the faint-hearted. Use an enclosed spray booth.