I am thinking of setting up a spraybooth in the garage with some removable lightweight panels so can put it together when required then put it out the way when finished. It will probably be about 4.5m x 3m x 2m high. I am just a little unsure of how much extraction to use. I was going to make it positive pressure and pump air in to avoid needing expensive explosion proof fans. Then just filter an outlet and run a duct outside. Was thinking along the lines of using one of the inline fans sold for growing plants and filter the incoming air, think the 8 inch flows about 700 cubic metres per hour would this be enough to get the over spray out.