Ask the Expert Question-and-Answer Archive

by Ron Joseph

May, 2007

Do I Need a Spray Booth?

Q: I have a very low .02 VOC cold liquid spray metal coating that is 95% solid. It is so heavy that when you spray it with an HVLP the over spray falls to the ground. Do I need a booth and if so could it be a booth that filters the air back into the shop so I don’t have to heat a 4,000 S/F warehouse with a make up air system?

A: Please bear in mind that the primary purposes of a spray booth are (i) to prevent fires and explosions, (ii) contain paint overspray and prevent it from entering the atmosphere, (iii) protect the health and safety of painters, and (iv) minimize the amount of overspray that deposits on freshly painted surfaces.

The last factor (iv) strictly concerns the operator, whereas the first three are governed by the EPA and/or OSHA.

Bulletin NFPA-33 is provided (at a small cost) by the National Fire Protection Association and lays out the guidelines for designing a spray booth.  According to this document the concentration of flammable vapors must not exceed 25% of the lower flammable limit (LFL).  In my opinion, based on the information you provided the VOC content of your coating is so low (0.02 lbs/gal), that it is unlikely that you will ever achieve such a high value. In any case, you mentioned that this is a liquid metal coating, and hence you might be exempt from requiring a spray booth.

The EPA requires the installation of spray booths primarily to prevent paint particles from entering the outside atmosphere, but since you mentioned that the particles are heavy and dropped to the ground, you might well be able to make the argument that a conventional spray booth is not required.

Unfortunately, it is not for me to make such determinations, but a quick consultation with your local fire marshal will determine if he requires you to install a spray booth to prevent a conflagration.

With regard to the EPA or your local state air pollution agency, a quick phone call to the appropriate permit engineer should answer the environmental requirement.

Recirculating spray booth air is commonly being performed and your main concern is to keep the concentration of solvents well below the permissible exposure levels (PEL).  Since your coating has such a low VOC content I imagine that you can quite easily recirculate the air several times before attaining any significant concentration level of solvents.

Spray booth manufacturers such as Global Finishing Systems, whose address and phone number you can obtain from the Internet can advise you on the recirculation issue.

I hope I have been somewhat helpful in answering your questions.

Regards,

Ron Joseph