Ok guys, no more picking on people's grammar in this thread or it gets locked. Let's just concentrate on the question, ok?
I would not put a furnace in a paint booth. Even if you keep it shut off when you are painting it will get crusted with lots of flammable and hazardous overspray and become both a fire and a health hazard. If you want to heat the booth run duct work and shut the furnace off when painting.
