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 https://www.osha.gov.

October 29, 1986

Mr. Shannon M. Simpson
Regional Sales Manager
P.O. Box 370
411 Bradford Street, N.W.
Gainesville, Georgia 30503

Dear Mr. Simpson:

This is in response to your letter of June 2, concerning testing equipment for use in potentially hazardous environments. Please except our apology for the delay in response.

The Occupational Safety and Health Administration (OSHA) requires that equipment intended for use in general industry applications, including hazardous locations, be listed or approved by a nationally recognized testing laboratory such as Underwriters Laboratories, Inc. (UL), or Factory Mutual Engineering Corp. (FM), except under the following circumstance. Custom-made equipment intended for use by a particular customer may be determined to be safe for the intended use by the manufacturer on the basis of test data. In such an instance, the employer is required to retain a copy of the manufacturer's test data for inspection by OSHA. Such custom-made equipment need not be listed or approved to be acceptable to OSHA for use by employees.

The following OSHA standards relate requirements for approved electric powered equipment for use by employees in general industry occupations: 29 CFR 1926.302(a); 29 CFR 1910.304(f)(5)(v); 29 CFR 1910.307(b); 29 CFR 1910.399(a)(1), (a)(2), (a)(7) and (a)(8).

Electric power operated equipment used by employees in construction industry applications is regulated under 29 CFR 1926.302(a). Such equipment is required to be either approved double-insulated type or its equivalent, or to be grounded and approved in accordance with OSHA requirement at 29 CFR 1926, Subpart K, per 29 CFR 1926.400(a). Therefore, OSHA required all portable electric powered equipment used in the construction industry to be approved and acceptable. Furthermore, equipment used in hazardous locations must be listed and approved for the circumstances of the hazard, per 29 CFR 1926.404(b). Listed tools are defined to be those approved by a national recognized testing laboratory such as UL or FM. Only a U.S. laboratory qualified as nationally recognized.

Pertinent portions of the OSHA general industry and construction standards are enclosed for your reference.

If we may be of further assistance, please contact us.


John B. Miles, Jr., Director
Directorate of Field Operations