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.

December 20, 1979

Mr. Raymond J. Husson
Senior Safety Representative
Bechtel Incorporated
Post Office Box 1709
Washington, D. C. 20013

Dear Mr. Husson:

This is in response to your recent inquiry requesting a clarification of standards for temporary wiring and temporary lighting in heavy construction.

The Occupational Safety and Health Administration's Construction Regulations, specifically 29 CFR 1926.401, require that lights shall be equipped with guards unless the bulb is deeply recessed. The lamp protection requirement, Item (g) of the National Electrical Code, does not satisfy the OSHA requirements for underground heavy construction.

In response to the three questions raised in your third paragraph, an insulated two-wire system for temporary lighting is acceptable. The two-wire system requires insulation approved for the location where the system is installed. The system cannot be used as a power source if the electrical tool is double-insulated because 29 CFR 1926.401(f) requires extension cords used with portable electric tools and appliances to be of the three-wire type. In addition, Article 305-2(d) of the National Electric Code requires all receptacles to be of the grounded type.

In response to the issue raised in your last paragraph, if cords are used to supply temporary lighting, the cords must be approved for hard usage, e.g., types "S, SO, ST and STO" as listed in Table 400-11 of the National Electric Code.

We hope this information is helpful. If we may be of any further assistance, please feel free to call or write.


Grover C. Wrenn Director,
Federal Compliance and State Programs