Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

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

November 16, 1999

Mr. Kenneth J. Yotz
Senior Vice President
Environmental, Management, and Training Systems, Inc.
919 St. Andrews Circle
Geneva, IL 60134-2995

Dear Mr. Yotz:

Thank you for your May 14, 1999 letter to the Occupational Safety and Health Administration's (OSHA's) [Directorate of Enforcement Programs]. In your letter, you develop a worksite scenario and then pose questions regarding verification of a lockout/tagout (LOTO) procedure by authorized employees pursuant to the Control of Hazardous Energy Standard, 29 CFR §1910.147, and the Electrical Power Generation, Transmission, and Distribution Standard, 29 CFR §1910.269. Your group LOTO scenario, your related questions, and our reply follow:

Scenario: As you know, 1910.147(d)(6) and 1910.269(d)(6)(vii) are virtually identical although the power generation standard contains an additional sentence clarifying that normally energized parts must be tested to ensure that they are de-energized. Because the facility where this issue arose is a power plant, the power generation standard would normally apply but, conceivably, circumstances may exist where LOTO is applicable.

At a power plant some LOTOs are rather simple and involve few workers. Others, however, such as a turnaround, involve many workers and multiple energy isolation sources which must be LOTOed. In addition, various trades are involved, each of which may hire workers from the local union hall. Task demands may require a varying number of workers on a given day. The preamble to these standards appears to require each authorized worker to walk down the system before starting work. Due to the complexity of the situation, few workers can fully determine whether all of the appropriate energy isolating devices have been LOTOed.

Work orders which detail the LOTO are prepared at this facility before each job is begun, a pre-job briefing is held, and a group LOTO box is used.

Question #1: The above identified standards concern verification. Must this verification be performed by each authorized employee or may one worker such as a supervisor or other representative perform the verification for all or for even a group of workers (i.e., each contractor or trade)?

Reply: As you have stated, the preambles to both standards [54 FR 36678 (September 1, 1989); 59 FR 4358, 4359 (January 31, 1994)] emphasize that each authorized employee must ensure that the hazardous energy control procedure has been implemented to isolate effectively the machine or piece of equipment. This verification step, which may require that workers walk through the affected work areas to verify effective isolation, must be accomplished before the authorized employees begin the servicing and/or maintenance work. You also state that normally energized parts must be tested to ensure that they are deenergized. Test instruments may be an appropriate means to verify machine or equipment deenergization, and such instruments are in fact required in the referenced power generation standard whenever employees are exposed to possible electrical hazards.

OSHA has recognized the need for an alternative to the verification requirement where complex LOTO operations involve many employees and numerous energy isolating devices. In such situations, the employer may designate a primary authorized employee, with the primary responsibility for a set number of employees working under the group LOTO device(s). The primary authorized employee must implement and coordinate the LOTO of hazardous energy sources and verify that the steps taken, in accordance with the specific energy control procedure, have in fact isolated the machine or equipment effectively from the hazardous energy sources. This must be accomplished before authorized employees participating in the group LOTO affix their personal lockout or tagout device to the group LOTO box and before they perform servicing/maintenance activities.

In addition to the primary authorized employee, each authorized employee participating in the group LOTO must be informed of their right to verify the effectiveness of the lockout measures, and each authorized employee must be allowed to personally verify that hazardous energy sources have been effectively isolated, if they so choose. An authorized employee, who opts to verify the effectiveness of the isolation measures, must perform this verification after affixing his or her personal lockout or tagout device to the lock box and before performing servicing/maintenance activities.

With respect to your concern that few workers can determine whether all of the appropriate energy isolating devices have been locked or tagged out, it is nonetheless imperative that the each authorized employee understands the hazards of the work and how to control the hazards. It is for this reason that OSHA requires, in paragraphs §1910.147(d)(1) and §1910.269(d)(6)(i), that authorized employee(s) have knowledge regarding the type and magnitude of the energy, the hazards of the energy to be controlled, and the procedure to be used to control the hazardous energy.

Question #2: Must each authorized employee physically walk down the system prior to beginning work or is it sufficient that they review the tests during the pre-job briefing and then "verify" that the group lock box remains locked prior to adding their lock to the box?

Reply: Each authorized employee, or alternatively the primary authorized employee as described above, must verify isolation of hazardous energy sources to the extent necessary to ensure that the servicing/maintenance can be performed safely. This may involve a walk through the affected work area(s), together with operations personnel, to verify effective isolation prior to beginning work. It is not sufficient for authorized employees, and primary authorized employees, to merely review tests in a job briefing and to rely on a locked lock box. Rather, each applicable energy isolation device must be verified to assure effective energy isolation.

Question #3: Under the circumstances identified in question 2 above, must each worker verify the LOTO by walking it down each day?

Reply: Yes. Verification is required on each shift before any authorized employee(s) begin work. An oncoming employee should not depend on the actions of another employee or supervisor, particularly one who has left the workplace for the day, for assurance that it is safe to work on the machinery or equipment. Additionally, specific procedures, as required by §1910.147(f)(4) and §1910.269(d)(8)(iii), must be developed and utilized to ensure continuation of LOTO protection for employees throughout the shift and during personnel changes.

Question #4: Under the circumstances identified in Question #3, must each worker verify the LOTO by walking it down each day the worker remains signed-on to the LOTO and though they do not remove their lock from the group lock box until their job has concluded perhaps several days later.

Reply: No, provided that each worker performing the servicing/maintenance work has had their lock(s) attached to the appropriate master lock mechanism since the last time they applied and verified that the hazardous energy was effectively isolated.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. Please be aware that OSHA's enforcement guidance is subject to periodic review and clarification, amplification, or correction. Such guidance could also be affected by subsequent rulemaking. In the future, should you wish to verify that the guidance provided herein remains current, you may consult OSHA's website at If you have any further questions, please feel free to contact the [Office of General Industry Enforcement at 202-693-1850].


Richard E. Fairfax, Director
[Directorate of Enforcement Programs]

[Corrected 3/4/2004]



1The same test instrument verification provision for electrical utilization systems is contained in the Electrical Safety-Related Work Practices Standard, §1910.333(b)(2)(iv)(B). (Back to text)