October 22, 2001

Wade R. Abnett, ASP
Senior Safety Engineer
Middle River Aircraft Systems
103 Chesapeake Park Plaza
Baltimore, Maryland 21220

Dear Mr. Abnett:

Thank you for your April 4 letter to the Assistant Commissioner of Maryland Occupational Safety and Health. Your letter was referred to Directorate of Compliance Programs (DCP) in the Occupational Safety and Health Administration's National Office for a response. This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any question -not delineated within your original correspondence. You requested a clarification regarding minimum face velocity requirements for spray booths as stated in 29 CFR 1910.107(b)(5) and 1910.94(c)(6)(i).

Question:   Must the average velocity range be no lower than Table G-10, while concurrently maintaining the 100 foot per minute (fpm) average requirement?

Reply:   Table G-10 of 1910.94(c)(6)(i) specifies the required airflow velocities ranging from 50 to 250 linear foot per minute (fpm) into the openings of a spray booth for various operations and designs, except where a spray booth has an adequate air replacement system. The standard 1910.107(b)(5)(i) is specifically for dry type overspray collectors, which are required to maintain the average air velocity of 100 linear fpm over the open face of the booth or booth cross section during all spraying operations except electrostatic spraying.

Question:   29 CFR 1910.107(b)(5) only refers to a dry filter spray booth. What is the minimum air velocity requirement for a waterwash spray booth or an enclosed booth with no openings?

Reply:   OSHA currently does not have specific standards addressing velocity requirements for a waterwash spray booth or an enclosed booth with no openings. However, 1910.94(c)(6)(ii) requires that the vapor concentration in all area of the booth remain at a level below 25 percent of the lower explosive limit (LEL). This requirement corresponds to the requirements of NFPA 33, section 5.2, Ventilation, performance requirements (2000 edition).

Question:   The attached OSHA interpretation (November 4, 1976 memorandum from Assistant Regional Administrator to Area Directors) referring to Table G infers that OSHA is directed to cite non-compliance of Table G only if the site has exceeded a Permissible Exposure Level (PEL) or 25% of the LEL. There is no mention of the 100 fpm requirement in 1910.107. Is this interpretation valid? Are there any more recent interpretations regarding face velocity?

Reply:   Yes, the 1976 interpretation memorandum is valid. However, please be aware that Permissible Exposure Levels (PELs) in working environments are addressed in 1910.1000, not in 1910.94 or 1910.107. The most recent interpretation regarding face velocity for spray areas is an April 8, 1997 letter to Ms. Elsie Munsell (enclosed).

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at http://www.osha.gov. If you have any further questions, please feel free to contact the Office of General Industry Compliance Assistance at (202) 693-1850.

Sincerely,




Richard E. Fairfax, Director
Directorate of Compliance Programs



cc:  Regional Administrator, Region III
      Dr. Keith Goddard, Assistant Commissioner of Maryland Occupational Safety
      and Health
      Enclosure