Having owned a body shop and built many paint booths over the years, I have developed an excellent design for one offs and "back-yard" types. While still using a used furnace motor and fan. The principle is very easy, DON'T draw out the overspray and fumes, rather "blow" them out. It's a positive pressure design. I will try to post some pics this weekend. I mount the fan inside a box with two HEPA furnace filters on the sides. This is mounted to the ceiling and outside wall of the paint booth and blow air into a wooden plenum, (~ 4' X 8' X 2') that is also mounted on the ceiling but inside the paint booth. The plenum has cut outs on one face and the bottom for 4 furnace filters. The entire booth is made out of sticks and poly. At the far end of the booth is my "door" and it has along the bottom edge 3 furnace filters. For those that are mathematically inclined, the number of filters "blowing" air into the booth exceeds those "exhausting" out, there for you get a pressure differential or positive pressure inside the booth vice ambient air outside. You will have a combination of cross flow and downdraught at the same time! The real benefit is that the positive pressure in the booth will not just blow out the exhaust but will serve to blow out every crack, crevice, joint, etc. in the booth, vice sucking in air, (dirty unfiltered air) from those same areas. I control the quality of air going in and the thus have a cleaner safer paint booth. "Sucking" the over spray and fumes out means having a potentially dangerous situation where the flammable fumes are drawn across an open electric motor as well as gumming up the fan blades very quickly. Mine is permanently mounted in a corner of my hanger and has folding walls that swing out of the way when not in use. Takes 5 minutes to set up when I need, of course that is not including moving everything out of the way first! LOL! Over the years this system has served me very well and produced some pretty darn good work.
Wayne I am more than happy to share any knowledge or experience I have with painting and finishing and leave that up to Larry. I am currently getting ready to paint my SCCA sports race car and will try to take plenty of pictures of the process and my home made paint booth. The booth is a pretty simple design with a down flow (air) idea. The idea is to basically pull air in from the top and filter exhaust air our of the bottom back side. Its a simple erector set style idea using ?2 X 3 lumber and polyethylene clear sheeting, a few dense micron furnace filters to draw air in from the top and push them out with a squirrel cage fan out of a used furnace to both filter and exhaust air out of the bottom. ?Its all put together using screws so that I can take it apart to store in my hanger. I have thought about re doing it with PVC pipes and PVC elbows to allow putting it together and taking it apart without using screws. Simply slip it together.? Jeff York KR2
