I started with this but had too much turbulence. The air coming in was centered and too concentrated so over spray had a tendency to curl back toward the filters. Also there was not enough lighting.
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One wall was plastic sheeting which easily let me know when I had the garage door adjusted for positive pressure.
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I replaced the plastic with drywall and added angles to the long walls of the booth. Moved the overhead lights to the angled portions to improve lighting on the sides of the vehicle. I wish I had just added more lights rather than moving them and plan to reinstall some overhead lights.
I also added lights on the walls so as to help light up the lower portions of the vehicle.
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Doubled the size of the filter bank to increase airflow and also doubled the amount of fans pushing air into the plenum (box) behind the filter bank. The filter specs have a flow rate to help you decided how many you need to facilitate the the airflow desired.
I am using squirrel caged fans from old home furnaces. They put out around 1200 cfm each and I have 4 of them.
Not saying may way is right or best by any means, I was never planning on restoring cars for other people, this was for my projects. So in my way of thinking I needed to move a "wall" of air from one end of the booth to the other, at a rate that changed in then entire mass of air contained in the booth twice per minute.
My booth is roughly 10x20x30' so 6000 cubic feet of air needs to be moved. 4 fans at 1200 cfm is 4800 cubic feet per minute but you have some flow restrictions with the plenum, filters and exhaust restriction to get a positive pressure. So a guesstimate puts me at 4000 cubic feet of airflow which changes the air mass in the booth every 1.5 minutes. Not quite what I was hoping for but a vast improvement.
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I have since changed to LED 6000k frosted bulbs.