Hmm, disappointing that the largest one is only 5' 5" tall at the peak, much less than that where you'd be "standing" (kneeling?)

Andy, if you have the 10x10 canopy already, couldn't you just surround it with cheap plastic "drop-cloth"?

During a time when forest fires made breathing the air here unhealthy, we had to stay indoors. We had several 20" box fans with high-efficiency filters taped over them so they were actively filtering the indoor air. You could use one or more of those pushing air into your enclosure, ideally with the air-escape points narrowed enough that you have positive pressure inside, so the only air coming in has to pass through the filter. Just tape the plastic sheet to the box fans

For a door to enter the space, they make stick-on zippers for just that purpose: hang your plastic sheet, stick on the zipper where you want it, then slit the sheet down the middle of the zipper. Works like magic if you remember to put the zipper on right-way-up. I watched my contractor do it wrong during a home remodel, zipper pull at the top so you pulled it down to open, didn't work! He had to unstick the zipper and do it over which was really difficult, but it's super easy if you start it right, zipper pull at the bottom when closed.

The only time I actually tried the plastic sheeting hung in a square as a "booth" was in 1976 or '77 at Santana, when we had prototype #1 done but no spray booth yet. We just hung plastic sheet from the ceiling to make a room within a room. No zipper, didn't know that trick, so you had to lift the edge of the sheet and climb under it. They had me paint the frame, though I had zero painting experience, I think because they knew it was going to be nasty and I was low man on the totem pole. I had no respirator whatsoever, so I tried to go in and hold my breath while I was in the "booth", but I still had metal-flake blue snot when I blew my nose later. And that was Imron, famously carcinogenic (though no one told me that at the time!) Shoulda reported them to OSHA...