This was mine. I now have a decent 10x12' spray booth room built into the new shop. in the new one I made a panel, like a window made of a section of foam and sheathing that I pull out and drop in my fan when i want to spray. So normally it looks basically like a solid wall with some trim around this one section, until I want to spray. I have full inlet filters on this now.
The old one was knock-down but only filtered the air going to the fan so it wasn't great in that regard (stuff could easily get into your finish). You can see the fan's shadow behind the filter in the middle there. I made it from 1/4" luaun plywood glued to 1.5" foam (IIRC). I painted the inside bright white for lighting purposes, and hinged them together with basic door hinges with pins I could knock out to break it down. The center section was a bit sturdier as it had to hold the fan. I got the fan from Grainger and found one that was pretty well sealed but not explosion proof ($$). Yes I took some chances, but I sealed up everything else that i could with silicone to minimize the risk of anything getting to see a spark. I also mostly spray water-based, so less of an issue. I called it my "explosion resistant" fan

and just put a long flex cord on it, so I could plug it in well away from the booth. I would take the fan off when I broke it down. I also made a lid for it out of 1/2-5/8" cheap plywood with a cutout to lay a 4' fluorescent light on top for extra lighting (first pic). I screwed in a clear plastic piece to the plywood to help seal the light away from any fumes. I also made a turntable from a lazy susan from HD which is helpful as others have pointed out (sitting on the horses, though not obvious). Once I had it set up, I would put 2" cheap masking tape over the hinge seams to direct airflow better and help keep bugs and stuff out was about all I had to do before starting. Oh yeah - I also put down a heavy canvas painters tarp before setting it up. Mounted a screw-in hook for the spray gun to hang it when I needed to. Just unscrew it when breaking it down. I bought a box of spray booth paper filters and stapled a few up over the opening to the fan. Never had to change them the few years I used this (sporadically).
It was kind of a PITA to setup/teardown, but I would batch things so I only set it up when I had enough to do. I always did it solo, but a helper would have made it a little easier. Yeah I put some thought into it... If you can find 1/8" plywood use it, but it needs to be able to take paint to make it white (hard to do with slick, dark brown hardboard)
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