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 21, 1998

Mr. Dimitrios S. Mihou, CSP
OSHA Regulatory Compliance /
Accident Prevention Specialist
Niagara Mohawk
300 Erie Boulevard West
Syracuse, NY 13202-4250

Dear Mr. Mihou:

This is a follow-up response to our interim letter of October 29, regarding your request for a clarification of the Occupational Safety and Health Administration's (OSHA's) standard, 29 CFR 1910.269, as it applies to aerial lift devices (e.g., bucket trucks).

In your letter, you indicated that the typical insulated aerial bucket trucks used by the industry are designed according to ANSI/SIA A92.2, which requires an insulated upper boom and a lower boom insert to isolate the chassis from the elevating boom section. Please find below, your specific questions and our responses.


Does this section of the standard (§1910.269(p)(4)) apply to typical insulated aerial bucket trucks used by the industry when used in an energized area.


This section applies to insulated as well as uninsulated aerial lifts, as §1910.269(p)(4) indicates that the insulated portion of an aerial lift operated by a qualified employee in the lift is exempt from the referenced Tables' (R6-R10) requirements specifying the minimum approach distances. The bucket trucks that are not insulated must comply with the requirements of the minimum approach distance Tables that are referenced in this section. Those lifts that have insulated portions (i.e., insulated upper boom), but could become energized, must comply with 1910.269(p)(4)(ii) and the pertinent sections that are referenced under this provision.


The chassis of insulated aerial bucket trucks may become accidentally energized when a conductor or other equipment have fallen or comes into contact with the lower section of the vehicle. Do the requirements of (p)(4)(iii)(A) through (p)(4)(iii)(C) apply to the lower section of the chassis for the occasion when it may become accidentally energized? Specifically, (p)(4)(iii)(C) requires grounding, bonding, ground mats and insulating protective equipment to be used to protect employees on the ground. Is this a requirements for insulated bucket trucks?


Please note that §1910.269(p)(4)(iii) states, if during the operation of the mechanical equipment, the equipment could become energized, the operation shall also comply with at least one of paragraphs (p)(4)(iii)(A) through (p)(4)(iii)(C) of this section.

Therefore, the requirements of these paragraphs would definitely apply to the lower section of the chassis for the occasion when it may become inadvertently energized. Further, the employer must comply with one or more of the requirements as outlined in Paragraphs, (p)(4)(iii)(A-C) if there is a potential for the lifts (insulated/non-insulated) to become energized.

Paragraph §1910.269(p)(4)(iii)(C) indicates that the measures used shall ensure that employees will not be exposed to hazardous differences in potential, and unless the employer can demonstrate that the methods in use protect each employee from the hazards that might arise if the equipment contacts the energized line, the measures used shall include all of the measures that you described, which are outlined in 1910.269(p)(4)(iii)(C)(1-4), such as grounding, bonding, ground mats, etc. If, for example, the employer can demonstrate the creation of an equipotential zone which will protect a worker standing within it from hazardous step and touch potentials then the employer may be relieved from the requirements set by 1910.269(p)(4)(iii)(C)(1-4). Such a zone can be produced through the use of a metal mat connected to the grounded object, and in some cases, a grounding grid can be used to equalize the voltage within the grid.

Please note however, that equipotential zones will not protect employees who are either wholly or partially outside the protected area. Bonding conductive objects in the immediate work area can also be used to minimize the potential between the objects and between each object and ground.

Finally, it is important to remember that the use of insulating equipment must be rated for the highest voltage that can be impressed on the grounded objects under fault conditions (rather than for the full system voltage).

Thank you for your inquiry. If you need further assistance, please contact Alcmene Haloftis of my staff at 202-693-1850.


Richard E. Fairfax, Director
Directorate of Compliance Programs