I also have seen all kinds of makeshift booths including some paint upwind specials. My fan has an enclosed motor but belt drive and I duct the motor ventilation from outside the air stream, from outdoor actually. I don't have explosion proof anything but the place clears well in orderly fashion and I have plugs and switches in the exhaust end near the fan outside the curtain, cord runs to fan and any recepts, lights upstream out of the way of the plume, I never get over spray on walls or even benches along side the job. Lights a couple feet down in ceiling and the major plume is drawn down along the floor and out. For a makeshift booth mine works really really well, being able to make it big enough as needed really lets one center project right in this downdraft situation, you can be painting up a storm and walk in to rest of building and never smell it.
When I do a major job put the end wall down and the air intakes from the ceiling, warmest part of the building and is drawn thru the booth. If I was going to be a regular winter painter (I can usually choose ambient friendly days) I would put in fared tube thru the booth, heat project, spray, heat.
I was doing some cleaning and remod work to it, dont think all the flashing was on in last pic but the whole thing is a "plug" that fits in my loading dock door, similar size to garage door, can be removed and stored elsewhere but I rarely use that part of the dock so thats its home, 6 wood screws hold it in.
I have screen and intake filter over it, can close the overhead on it in winter. A lot of peices I put on skids or boxes, can spin around into light and work from upwind.
