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NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.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

October 5, 1999




Thank you for your July 16, 1998 memorandum to the Directorate of Compliance Programs recommending the revision of 29 CFR §1910.147, "The control of hazardous energy (lockout/tagout)" standard. Please be advised that, after reviewing this standard in accordance with the Regulatory Flexibility Act, and Executive Order 12866, the Occupational Safety and Health Administration (OSHA) has decided not to amend the standard at this time. The purpose of this memorandum is to address the issues raised in your memorandum.

The Unexpected Energization Issue

Issue No. 1: "Unexpected energization" is not defined in the standard and you believe its intended meaning would equate to something like "any potential energy activation that may cause injury." You have encountered cases where the power to machines or equipment has been left on purposely and the task (which you thought should require lockout) was performed while employees worked around the powered machines or equipment. Since the machines were continually operating, some respondents' attorneys have argued that the energization was not unexpected, since the employee (who may have been injured) knew that the equipment was operating. As such, you request further clarification of the standard's scope and application.

Reply: Requirements for the protection of employees against the hazards associated with machines and machinery are set forth in both 29 CFR Subpart O, "Machinery and Machine Guarding" (§1910.211, et. seq.) and in §1910.147. Normal production operations are generally covered by Subpart O. Section 1910.147, on the other hand, covers servicing and maintenance activities (as defined in subsection (b) of the standard) performed during normal production operations if either of the circumstances set forth in subparagraph (a)(2)(ii) pertain.

As to your issue, although the term "unexpected energization" is not defined in the standard, §1910.147 applies when servicing and maintenance activities take place during normal production operations if either of the circumstances in the subparagraph either (a)(2)(ii)(A) or (B) apply and the subsequent exception is inapplicable. Under no circumstances is an employee ever permitted to place any part of his or her body within a hazardous area, such as the point-of-operation or ingoing nip point area, while the equipment is running or energized (unless the employee is engaged in certain minor servicing activities performed during normal production operations and alternative measures which provide effective protection have been taken).

Our determination is not affected by the fact that the standard's "scope, application and purpose" provision, §1910.147(a)(1), describes the standard as applying to "the servicing and maintenance of any machine and equipment of equipment in which the unexpected energization or startup of the machine or equipment, or the release of stored energy, could cause injury." In General Motors Corp., Delco Chassis Div., 17 BNA OSHA 1217, 1995 CCH OSHA ¶ 30, 793 (Numbers 91-2973, 91-3116, 91-3117, 1995), aff'd., 89 F.3d 313 (6th Cir. 1996), the Review Commission and the United States Court of Appeals for the Sixth Circuit held that the standard does not apply if energization would not be unexpected, i.e.-- if employees would be aware under the circumstances that energization was about to occur.

Although one might argue, by way of analogy, that there can be no hazard of unexpected energization during servicing and maintenance because the machine or piece of equipment was already operating or energized, we do not believe that the Delco decision can be applied to this described situation. In Delco, the issue was the meaning of the term "unexpected" in the context of a machine which had been shut down for servicing. The Commission and the court had no occasion to consider machine servicing during operation, which the standard addresses and prohibits with certain limited exceptions.

Furthermore, machines or pieces of equipment which are energized and not in the production cycle may not necessarily pose "unexpected energization" hazards, but they certainly could pose employee hazards from "the release of stored energy" or "unexpected startup [activation] of the machines or equipment ". The preamble on page 36661 to the Final Rule, as published in the Federal Register, 54(169), Friday, September 1, 1989, addresses the issue as it states:

"In those circumstances, when there is potential for unexpected activation or energy release and the machine or equipment can be deenergized to perform the servicing [or maintenance], the standard requires it to be deenergized and be locked out or tagged out in accordance with the procedure required by this standard."

Issue No. 2: The standard appears to apply only to the specific piece of equipment where the servicing and maintenance work is performed. However, when employees are working on a piece of equipment or machinery, additional hazards associated with adjacent or auxiliary equipment or machines may pose hazards to these employees. The standard does not appear to adequately address the issue.

Reply: If an authorized employee(s), who is performing servicing or maintenance activities, is exposed to the unexpected energization, start up, or release of stored energy from interconnected or nearby machine or equipment, the energy control procedures for all hazardous energy sources must be implemented. This same policy applies to employees exposed to hazardous energy while they are performing servicing and maintenance activities during normal production operations.

The standard requires that employees be protected when performing servicing or maintenance; in this case, all components and/or nearby machines or equipment posing employee hazards must be shut down and locked/tagged out to protect the authorized and affected employee(s). Conversely, the machine guarding Subpart O requirements would apply in the scenario where an authorized employee is performing servicing or maintenance activities on one machine and is exposed to machine hazards from an adjacent machine or piece of equipment in the normal production mode of operation (without service or maintenance activities taking place).

Issue No. 3: The final issue with regard to unexpected energization relates to machines that have a series of (multiple) sequential activation methods which the Review Commission has deemed to be of a complex and intended nature so that any energization or start up would not be unexpected. The problem with this rationale is that it does not account for system failure such as an electrical fault that may cause the machine to operate even though all the controls are not activated. Further, while the energization or start up is not unexpected by the employee turning on the machine, it may be wholly unexpected to the employee servicing the machine.

Reply:In addition to the above legal description, please refer to the attached October 30, 1996 Regional Administrators' memorandum on the "Enforcement of 29 CFR 1910.147, the Control of Hazardous Energy (LOTO)" for guidance regarding the enforcement of the LOTO standard with respect to the General Motors Corporation, Delco Chassis Division decision.

Routine & Repetitive

Issue No. 4: Additional clarification is needed with regard to the exception to paragraph(a)(2)(ii) of the §1910.147 standard. Some employers only want to shut off the machine at the control circuit and allow employees to work without additional safeguards, they claim that the work is routine, repetitive, and integral to production, even though it creates significant exposure to employees performing the task. Some employers have contended that the safeguard for alternative protection is to shut off the equipment which would meet the Subpart O requirements, even though there may be a potential to an unexpected energization or start up. The additional safeguard provision needs to be expanded with additional safety measures in conjunction with Subpart O. The standard fails to provide specific "minor servicing" examples.

Reply: Some servicing operations performed during normal production operations are excepted from coverage under the standard. The lockout/tagout standard is not intended to cover certain minor servicing activities, which are necessary to carry out the production process, provided that associated danger zones are properly safeguarded. The machine guarding standards in Subpart O cover these types of operations. By merely shutting down the machine, the employer does not protect the operator and other employees (from normal production operation hazards) because the machine or piece of equipment can be easily turned on. Simply shutting off a machine is not a recognized machine safeguarding method.

The lockout/tagout standard contains specific criteria for the minor servicing exception. The three criteria determine if the minor servicing exception would apply to a particular activity.


  1. The activity must take place during, and must be inherent to, normal production operations (which include the utilization of a machine or piece of equipment to perform its intended production function). These functions would be carried out by employees with the machine or equipment energized. They may include minor servicing activities (i.e., clearing of jams; minor cleaning or adjustments; lubrication) that safely take place while the process is performed in situations where extensive disassembly of the machinery/equipment is not required.
  2. The activity must be:


    • Routine: The activity must be a regular course of procedure and be in accordance with established practices.
    • Repetitive: The activity must be repeated as part of the production process or cycle.
    • Integral: The activity must be inherent to the production process.
  3. If all of these apply, the employer must use alternative measures to provide effective protection from the hazardous energy.

Several examples of alternative means of safeguarding are presented by the national consensus standard, American National Standard Institute (ANSI) B11.19, as well as other safeguarding control techniques presented in a various equipment/ machine specific ANSI Standards (e.g., ANSI B65.1 for Printing Press Drive Controls). Although these standards are not inclusive, they describe several effective employee safeguarding alternatives, such as, but not limited to:

  • remote oilers or other remote devices;
  • interlocked barrier guards; and
  • two hand safety control devices or control devices located at a safe distance from the hazardous energy source.

These alternative measures must enable the employee(s) to safely perform the servicing activity without being exposed to the types of hazardous energy covered by this standard. In summary, activities which do not meet each and every element of this minor servicing test are not entitled to the exception and continue to fall within the coverage of the LOTO standard.

We hope you find this information helpful. If you have any further questions, please feel free to contact the Office of General Industry Compliance Assistance at (202) 693-1850.