October 16, 1987

Mr. David K. Branstutter
P.O. Box 178241
Lucasville, Ohio 45699-0001

Dear Mr. Branstutter:

This is a follow-up to our September 18 response to your letter dated September 1, addressed to Mr. E. Ross Buckley, Chairman, Occupational Safety and Health Review Commission, concerning the recirculation of air discharged from paint booths and the use of electronic air filters to filter the recirculated air. Your letter has been referred to the Occupational Safety and Health Administration (OSHA) for response.

Section 29 CFR 1910.107 of OSHA's General Industry Standards applies to spray finishing operations using flammable and combustible materials. Paragraph (d)(9) of this Section (copy enclosed) specifically prohibits recirculating air discharged from spray operations. However, if the workplace is in compliance with a current industry consensus standard, or if the employer's workplace is at the state-of-the-art and provides equal or greater safety and health protection to the workers but differ from OSHA's requirements, a violation of the applicable OSHA standard may be considered to be de minimis (see enclosure).

The National Fire Protection Association (NFPA) 33-1985 standard paragraph 5-6.1 allows the recirculation of air discharged from a spray operation if the recirculated air has been decontaminated to an acceptable level. In addition, the same NFPA standard required that the decontaminated air stream be monitored by approved equipment that signal the operator and automatically shutdown the spray operation in the event of failure of the decontamination equipment. Therefore, if you desire to recirculate air discharged from paint spray booths, you must meet or exceed the requirements of NFPA 33-1985 paragraph 5-6.1.

There are several air cleaning mechanisms in use including filtration, absorption, adsorption, centrifuging, electrostatic precipitation (electronic filter), and incineration. Electrostatic precipitators are mainly used to collect particulates and not gases and vapors. For your purpose, to remove gases, vapors and particulates, a combination of electronic and absorption cleaning devices may be necessary.

Section 29 CFR 1910.107(c)(5) of OSHA's General Industry Standards in part reads, "Unless specifically approved for locations containing both deposits of readily ignitable residue and explosive vapors, there shall be no electrical equipment in any spraying area, whereon deposits of combustible residues may readily accumulate..." Therefore, since electrostatic precipitators produce sparks, the use of such devices in a spray area where flammable liquids are used must be engineered to meet the requirements of the above standard.

OSHA does not endorse or promote any products. Therefore, we cannot recommend any particular manufacturer of electronic air filters. The Thomas Register of American Manufacturers does contain names, telephone numbers, and addresses of the manufacturers of air cleaning equipment, electronic air filters and air contaminant monitors. You may wish to contact these firms for the information you need. Thomas Registers are available in most public libraries. We recommend, however, that you check with the manufacturer of the electronic air filter of you choice to assure that the equipment will safely remove the type of contaminant in your spray area. Additionally, you may explore the feasibility of using heat pumps to extract heat from the air discharged from your spray booth.

I hope this information is useful to you.

Sincerely,



Edward J. Baier
Director
Directorate of Technical Support


Enclosures



September 1, 1987

E. Ross Buckley, Chairman
Occupational Safety and Health Review Commission
1825 K Street, N.W.
Washington, D.C. 20006

Dear Mr. Buckley,

I own a body shop and am losing alot of heat due to my paint booth. Currently, I use a blower (with common air filters) to supply shop air to the paint booth and another blower forces the paint-contaminated air out an exhaust vent.

What I would like to do is recirculate the air back into the shop and prevent any heat loss. I can use filters to catch the paint particles, but I am not sure if an electronic air filter will remove paint fumes.

It is my understanding that there are industrial electronic air filters and they are capable of removing all types of toxic fumes. If at all possible, would you please supply me the names and addresses of companies which manufacture industrial electronic air filters? Also, would you please recommend a couple models?

Incidentally, if I can safely recirculate the paint booth's air back into my shop area, are there any devices I can buy which will permit me to monitor the air to ensure my industrial electronic air filter is working properly?

I would appreciate a response concerning this matter as expeditiously as possible.

Sincerely,



David K. Branstutter
P.O. Box 178241
Lucasville, Ohio 45699-0001