HI all, my spray booth uses a 3000cfm fan in the attic.my booth is 8ft x6ft by 8ft high, thats a complete air change every 8 seconds, and that is just about right. when you are spraying, you are surrounded by about 10% mist, but when you finish your pass, about 3seconds and the air is clear.
Rcpete PS, you must not forget to leave a door open some where in the house for makeup air.