As stated in a couple posts above, the chance of creating an explosive atmosphere in your setup is extremely remote. Takes a threshold air/fuel ratio to get there and it would be hard to do w/o vent fan, let alone with one. I would worry more about being hit by a falling airplane, swallowed by the earth opening up in an earth quake, etc.
My (hobby) stick framed and drywalled booth has seen many, many paint jobs going thru and not a whimper. I use the squirrel cage blower from an old 5000cfm swamp cooler blowing out w/ 1/2hp induction motor directly in the air flow. This setup changes the air in the room every minute or so. I never even come close to generating a cloud. Of course I use a spray mask but I'd bet if you didn't stand between the fan and my spray gun, you would probably be challenged to smell the paint!
I did a search on Yahoo for "Paint Booth Explosion" and found zero incidents, and that's a pretty good endorsement since gory web pictures are a staple when they exist. I did take some precautions such as embedding 14 4' fluorescent fixtures in the walls and ceiling and covering each with a clear poly sheet but that is more to protect the lights form me running into them and breaking them and from me spray painting them. Another reason for going florescence is the light color. The whiter the light the truer the color you see in your booth. Lighting is rated according to its Correlated Color Temperature (CCT) is a measure of the "shade" (electromagnetic wave length)of whiteness of a light source. It is listed in the units of degrees Kelvin or the equivalent light wave length given off by by a 'blackbody' (hypothetical perfect radiation emitter) glowing at that temperature. Incandescent lighting is rated at 2700K which is yellowish-white and isn't the best in an environment like a paint booth where you are trying to carefully adjust the color that will be seen in a daylight setting. Halogen lighting is 3000K which is an improvement. Fluorescent lamps are manufactured to a chosen CCT by altering the mixture of phosphors inside the tube. Warm-white fluorescents have CCT of 2700K and are popular for residential lighting. Neutral-white fluorescents have a CCT of 3000K or 3500K. Cool-white fluorescents have a CCT of 4100K and are popular for office lighting. The latter two are better for a paint booth compared to incandescent lighting. Daylight fluorescents have a CCT of 5000K to 6500K, which is bluish-white and are the best possible lighting for a paint booth. They really suck for lighting a home though. That's why the make the 2700K warm light versions. Plain vanilla 4100K cool-white bulbs are great but I sprung for the 5000K Daylight ones in my booth. Don't know if I can really tell a difference but what the hey!! Either are tons better than regular incandescent light bulbs were.
IF your setup ever did pop, you would launch that tarp cover to the stratosphere and be running in circles saying 'Where's my mama?' for a few moments but shouldn't suffer any real bodily harm.
To make a short story long, yes there is a potential for an explosive mixture of paint fumes and air, no doubt about it. However the simplest precautions completely avoid that possibility and your setup far exceeds that requirement. "Paint on Garth!!"
Last edited by firstname.lastname@example.org; 07-10-2009 at 08:46 AM.