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.

April 10, 2017

Mr. Dan Reider
Buford Goff & Associates, Inc.
Engineers and Planners
1331 Elmwood Avenue
Columbia, South Carolina 29201

Dear Mr. Reider,


Thank you for your letter to the Occupational Safety and Health Administration (OSHA). Your letter was referred to OSHA’s Directorate of Enforcement Programs for a response to your questions. In your letter, you mentioned that you work for an engineering firm in Columbia, South Carolina, and have questions regarding OSHA’s requirements related to welding and recirculation of filtered air back into technical college classrooms or workplaces. You were also called by a member of my staff to clarify some of your questions. 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. Your specific questions and our responses are below.

Background: You explained that your company helps design classrooms and laboratory facilities in schools and technical colleges where students are learning the welding trade, and that those facilities may be equipped with ductless welding booths that allow recirculation of filtered air back into the classroom (or, if the booths are used in industry, into a workplace). You are concerned about the potential hazards from welding fumes, especially from hexavalent chromium, which is a carcinogen. You also referenced an OSHA publication, Table III: 3-6., Recirculation Criteria, from the OSHA Technical Manual (OTM), Section III, Chapter 3, Ventilation Investigation, which states that "Recirculation should not be used if a carcinogen is present."

Question 1: The OSHA language consistently references "workers." Do OSHA’s requirements also apply to students in classrooms of technical colleges?

Response: The Occupational Safety and Health Act of 1970 (OSH Act) covers most private sector employers and their employees either directly through Federal OSHA or through OSHA-approved State programs. In general, whether an employment relationship exists is a legal determination that must be made on a case-by-case basis.

Several factors influence whether a student performing work activities as part of an educational or training program is engaged in an employment relationship. In most cases, a student receiving compensation in exchange for performing work activities would be considered an employee by Federal OSHA. Generally, compensation includes wages or a salary, although other forms of compensation may include receiving room and board, or counseling. On the other hand, if a student receives no monetary or other compensation for work performed, it is Federal OSHA’s view they are not an employee and not subject to Federal OSHA standards.

The OSH Act provides that states may assume responsibility for enforcing OSHA standards by adopting a State Plan; roughly half of U.S. states have done so. See www.osha.gov/dcsp/osp, for a listing of State Plans and contact information. Since your welding projects could be located in State Plan states, you may want to contact the states directly for guidance. Also, in some states, students performing work activities at schools or technical colleges may be considered employees of state or local governments. Federal OSHA specifically excludes coverage of public sector employees; however, State Plans are required to provide coverage of employees of state and local governments. You may also want to inquire of these states whether their standards apply to students in public institutions.

Finally, the National Institute for Occupational Safety and Health (NIOSH) has a Safety Checklist Program which provides information needed by career-technical schools and colleges to maintain safe classrooms, shops, and laboratories for both teachers and students. Details of the NIOSH Safety Checklist Program are available at: www.cdc.gov/niosh/docs/2004-101/. A NIOSH self-inspection checklist on general requirements for welding, cutting, and brazing is available at: http://www.cdc.gov/niosh/docs/2004-101/chklists/r1n64w~1.htm.

Question 2: Since hexavalent chromium from welding stainless steel is classified as a carcinogen, why do manufacturers of ductless welding booths allow recirculation into the workplace (or into the classroom, if used in technical colleges)? Central dust collection system manufacturers also allow recirculation into the workplace. They state that recirculated air is permissible, so long as the air is properly filtered and monitored. I am not sure how either of these comply with Table III: 3-6 in the OSHA Technical Manual (OTM).

Response: OSHA’s standard at 29 CFR 1910.1026 (Chromium (VI)), governs occupational exposure to hexavalent chromium. The OSHA standard sets the permissible exposure limit (PEL) for hexavalent chromium at 5 micrograms per cubic meter (5 µg/m3) in air, calculated as an 8-hour time weighted average (TWA) (29 CFR 1910.1026(c)). Employers generally must use engineering and work practice controls to reduce and maintain employee exposure to hexavalent chromium at or below the PEL (29 CFR 1910.1026(f)(1)(i)). Wherever feasible engineering and work practice controls are not sufficient to reduce employee exposure to or below the PEL, employers must supplement them by the use of respiratory protection (29 CFR 1910.1026(f)(1)(i), (g)). Additional information is available in OSHA’s Chromium (VI) standard, and the compliance directive for the standard, CPL 02-02-074, Inspection Procedures for the Chromium (VI) Standard, which explains that several factors affect chromium levels in welding fumes.

Employers generally determine 8-hour TWA exposures to hazardous air contaminants, like hexavalent chromium, by conducting personal air monitoring for workers. If monitoring results indicate that exposures exceed an applicable PEL, eliminating recirculation of air into the workplace by modifying or updating the ventilation system can reduce exposures and assist in achieving compliance. Consultation with equipment manufacturers and/or a ventilation expert is advisable to ensure that any existing engineering control modifications or new installations are adequate to meet the ventilation needs of the application and the facility, and to protect workers.

OSHA encourages employers to go beyond the minimum requirements set forth in OSHA standards when it is possible to do so. Although not necessarily required by the Chromium (VI) standard, the best practice for ventilating areas where carcinogens are present is to filter and exhaust the air to safe, non-occupied locations, where it cannot re-enter the building through the fresh-air inlets of the building’s air-supply system.

The OTM’s primary purpose is to provide technical information about workplace hazards and controls to OSHA’s Compliance Safety and Health Officers. The information contained in the OTM is not a substitute for OSHA standards and it is not used for establishing Agency compliance policies. OSHA makes the OTM available to the public for use by other health and safety professionals, employers, and anyone involved in developing or implementing an effective workplace safety and health program. You may also find helpful OSHA’s public Safety and Health Topics webpage on Welding, Cutting and Brazing. Highlighted on this page is a useful fact sheet, Controlling Hazardous Fume and Gases during Welding.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA’s requirements are set by statute, standards, and regulations. Our letters of interpretation do not create new or additional requirements but rather explain these requirements and how they apply to particular circumstances. This letter constitutes OSHA’s interpretation of the requirements discussed. From time to time, letters are affected when the Agency updates a standard, a legal decision impacts a standard, or changes in technology affect the interpretation. To assure that you are using the correct information and guidance, please consult OSHA’s website at www.osha.gov. If you have any further questions, please feel free to contact the Office of Health Enforcement at (202) 693-2190.



Thomas Galassi, Director
Directorate of Enforcement Programs