Air Flow in Painting Facilities

Ask the Expert Question-and-Answer Archive

by Ron Joseph

October, 2002

Air Flow in Painting Facilities

Q. Regarding paint booth air flow dynamics, we have been using as a rule of the thumb the following two constraints:

air supplied from the paint line tunnels: minimum requirement = 200 ft/minute
air flow across the part to be painted: minimum requirement = 120 fpm.

However, nobody can provide me with the source of these requirements. Are there regulatory requirements for minimum air flow in paint booths. If so, where might I find them.

A. Your best source for information on airflow is NFPA-33 for spray booths and NFPA-86 for ovens. I haven't read through NFPA-86, but I'm fairly confident you'll get your answer there. Both documents can be purchased online at www.nfpa.org, but they are not for free. I downloaded both of them for approximately $26 each.

With regard to the spray booth, you will find that the minimum velocity used to be 100 ft/min, but in the last year or two this has been changed so that the Lower Flammable Limit (LFL) is now the new criterion and not airflow. To the best of my knowledge, the maximum LFL should be 25%, but I suggest that you check this for yourself.

OSHA also has a regulation on spray booths, I believe it is 1910, and you can go to the OSHA site and find it there. OSHA tends to work closely with the NFPA on these issues.