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.


DATE: March 3, 1992




Directorate of Compliance Programs
Directorate of Compliance Programs
Directorate of Compliance Programs
SUBJECT: Contractor shop-made extension cords.


This is in response to your November 13 memorandum requesting an interpretation of OSHA requirements pertaining to shop-made extension cords. I apologize for the delay in responding to you.

Normally, equipment must be approved as an assembly by a nationally recognized testing laboratory before it would be acceptable under the General Industry or Construction Electrical Standards (Part 1910, Subpart S and Part 1926, Subpart K, respectively). In the case of cord sets used in construction, it is common for them to be assembled in the field by electrical contractors. It should be noted that OSHA interprets cord sets as being temporary wiring extensions of the branch circuit. As such, temporary electrical power and lighting wiring methods, as specifically modified in 1926.405(a)(2) and 1910.305(a)(2), may be of a class less than that required for a permanent installation. Thus, temporary electrical power and lighting installations are permitted during the period of construction, remodeling, maintenance, repair or demolition of buildings, structures, equipment, or similar activities. In addition, temporary wiring must be removed immediately upon completion of construction or purpose for which the wiring was installed. When the temporary wiring consists of shop-made cord sets, self-fabricated lighting installations, emergency or experimental wiring etc., as permitted by 1926.405(a)(2) and 1910.305(a)(2) to be assembled and installed at the work site using approved parts, the requirement for listing by a nationally recognized test laboratory does not apply. If a factory-manufactured temporary wiring assembly, such as ready-made extension cords, temporary lighting strings (UL-1088), "on-the-spot" emergency lighting, etc., is desired, then the prefabricated temporary wiring assembly to be installed must be of a type that a nationally recognized testing laboratory accepts, certifies, lists, labels, or determines to be safe.

In regard to electrical contractors assembling cord sets at construction sites, the practice is acceptable, provided the assembled cord sets are constructed in a manner equivalent to those that are factory-assembled and approved. (The same approach applies to the General Industry Electrical Standards. However, your question pertained to construction, so the remaining references are to Subpart K of Part 1926.) Criteria for determining whether shop-made cord sets meet existing electrical standards include:





  1. All components must be approved for the purpose by a nationally recognized testing laboratory (1926.403(a)). Individual components must be compatible for use with the other components of the completed assembly.
  2. The cord set must meet all applicable requirements of Subpart K. For example, the assembly must be marked appropriately (1926.403(g)); boxes intended for use in a permanent installation may not be used (1926.403(b)(1)(i)); cords must be connected to devices and fittings so as to provide strain relief (1926.405(g)(2)(iv)); cords passing through holes in enclosures must be protected by bushings or fittings designed for the purpose (1926.405(g)(2)(v) – fittings designed to fasten cables to metal boxes are not acceptable); and no grounded conductor shall be attached to any terminal or lead so as to reverse designated polarity (1926.404(a)(2)).
  3. The cord set must be assembled by a qualified person.
  4. The wiring of the completed assembly must be checked before the cord set is first used. For example, the following, or equivalent, tests should be performed:
    (a) All equipment grounding conductors shall be tested for continuity and shall be electrically continuous.

    (b) Each receptacle and attachment plug shall be tested for correct attachment of the equipment grounding conductor. The equipment grounding conductor shall be connected to its proper terminal.

[Corrected January 22, 2008]