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.

January 12, 1979

MEMORANDUM FOR:     CURTIS A. FOSTER
                    REGIONAL ADMINISTRATOR - DENVER

THRU:               DONALD E. MACKENZIE Field Coordinator

FROM:               IRVING WEISBLATT, Acting Director,
                    Directorate of Federal Compliance and State Programs

SUBJECT:            Clarification of 1910.309(c)(2) and 1926.400(1)(2):
                    Ground Fault Protection

In the specific instance on a construction site, where the permanent wiring is in place and in use, and an employee plugs an extension cord into a permanent 120 volt, single-phase receptacle outlet, and then plugs a portable electric tool into the extension cord, a GFCI may be used but is not required. However, if the GFCI is not used under these conditions then and assured equipment grounding conductor program is required covering all cord sets, receptacles which are not a part of the permanent wiring of the building or structure, and equipment connected by cord and plug.