August 25, 2025

John D. Smart
Bell Nunnally Attorneys & Counselors
3232 Mckinney Avenue, Suite 1400
Dallas, TX 75204

Dear John D. Smart:

Thank you for your letter to the Occupational Safety and Health Administration (OSHA), requesting a letter of interpretation regarding the application of OSHA standards to electrical busway hot swappable plug-in units. This constitutes OSHA’s interpretation only of the information discussed and may not be applicable to any questions not delineated within your original correspondence. The background information and your questions are paraphrased below, and our responses follow.

Background: A number of companies manufacture and sell plug-in units for energized track busways that are designed to be "hot swappable," meaning they are capable of insertion into and removal from an energized track busway.

Question 1: Is the insertion or removal, of a hot swappable plug-in unit for an electrical track busway covered under §1910.333(c)?

Response 1: Yes, 29 CFR 1910.333(c), Working on or near exposed energized parts, “applies to work performed on exposed live parts (involving either direct contact or contact by means of tools or materials) or near enough for employees to be exposed to any hazard they present.” Employees inserting or removing plug-in devices on energized electrical track busways are performing work near enough to the hazards of exposed live parts. NFPA 70E (2021) table 130.5(C) explicitly states that there is a likelihood of occurrence of an arc flash incident when there is an insertion or removal of plug-in devices into or from busways involved, regardless of its operating conditions.

Question 2: Does 29 CFR 1910.333 require an employer to deenergize track busways before permitting a qualified employee to insert or remove a “hot swappable” plug in unit from the track busway?

Response 2: In accordance with 29 CFR 1910.333(a)(1), live parts to which an employee may be exposed shall be deenergized before the employee works on or near them, unless the employer can demonstrate that deenergizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations. If the exposed live parts are not deenergized (i.e., for reasons of increased or additional hazards or infeasibility), other safety-related work practices shall be used, in accordance with 29 CFR 1910.333(a)(2), to protect employees who may be exposed to the electrical hazards. Other safety-related work practices may include but are not limited to proper use of special precautionary techniques, personal protective equipment, insulating and shielding materials, and insulated tools. Additionally, in accordance with 1910.333(c)(2), only qualified employee(s) may work on energized electric circuit or parts, provided the employee meets the training requirements of 1910.332 (b), and uses other safety related work practices.

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 http://www.osha.gov. If you have any further questions, please feel free to contact the Directorate of Enforcement Programs at (202) 693-2100.

Sincerely,

Erin P. Gilmore, Acting Director
Directorate of Enforcement Programs