I erect a plasic wall on 3 sides of my shop witht he door being the one without. the door(16') gets opened enough to put 2 squirrell cage fans on both ends and in between is sealed off. I have 2 windows on the opposite end that I open and put furnace filters on. the shop gets a thorough cleaning before I put up the walls. been workin pretty good so far.
as for fans, I though I read that the main problem that can result is with startup. that's when sparks can happen, so my fans are turned on before I start spraying and dotn get turned off until im done.
got done last sunday spraying a 19' sleekcraft boat that wouldn't fit all the way in my shop without a major rearranging, so I had the door open. luckily, only the trailer tongue was outside and it was raining lightly, so dirt in cc was minimal and not hard to fix.