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Standard Interpretations - Table of Contents
• Standard Number: 1910.147; 1910.333(b); 1910.399

November 16, 2000

Robert Weaver, Safety Coordinator
M&W Contractors, Inc.
P.O. Box 2510
East Peoria, IL 61611-0510

Dear Mr. Weaver:

Thank you for your November 3, 1999 letter to the Occupational Safety and Health Administration's (OSHA's) Directorate of Compliance Programs (DCP). You requested an interpretation for the definitions of "authorized employee" under 29 CFR 1910.147(b) and "qualified person" under 29 CFR 1910.399 as they pertain to verifying that a zero energy state exists on electrical equipment. You also have questions regarding 29 CFR 1910.147(d)(6) with regard to the verification of energy isolation for mechanical equipment. You indicated that your company is a construction company providing services to general industry clients.

As you seem to recognize, there are two standards that are most directly applicable to the circumstance described in your letter: 29 CFR 1910.147, The control of hazardous energy (lockout/tagout), and 29 CFR 1910.333, Selection and use of safe work practices. Section 1910.147 covers the servicing and maintenance of machines and equipment in which uncontrolled hazardous energy could cause injury to employees. Section 1910.333(b) provides procedures to protect employees who are working on or near exposed de-energized electric parts. Both standards mandate the use of locks and/or tags to control potentially hazardous energy.1

Please be aware that 1910.147 does not cover construction activities, or the maintenance of electric power generation, control, transformation, transmission and distribution lines and equipment. To the extent that you are engaged in construction, you must comply with the lockout and tagout provisions of 29 CFR Part 1926. See, e.g., 1926.417 and 1926.555(a)(7). To the extent that you are engaged in the maintenance of electric power generation, control, transformation, transmission and distribution lines and equipment, you must comply with the hazardous energy control (lockout and tagout) procedure provisions of 1910.269.

Your scenario, key definitions, questions, and our replies follow:

Scenario: A normal (group lockout) procedure for our employees working on mechanical equipment would be for our supervisor to accompany the host employer's representative to witness the shutdown and isolation of the necessary energies (e.g., mechanical energy; electrical energy.) As each lock is placed, the key is placed in the group lockbox and it is checked off the permit. The host employer's authorized representative then verifies the zero energy state by attempting to start the equipment. In the case of electrical shut offs a qualified electrician (employed by the host employer) shuts off the breaker or switch, and then tests the circuit to ensure it is off.2

Definitions: Pursuant to 1910.147(b), an "authorized employee" is a person who locks out or tags out a machine or piece of equipment in order to perform servicing or maintenance on that machine or equipment.

An "affected employee" is a person whose job requires him/her to operate or use a machine or equipment on which servicing or maintenance is being performed under lockout or tagout or whose job requires him/her to work in an area in which such servicing or maintenance is being performed.

According to Section 1910.399, a "qualified employee (person)" is an individual familiar with the construction and operation of the equipment and the hazards involved.

Question 1: May an authorized employee or a qualified employee (person) verify a zero energy state for mechanical equipment?3

Reply: Whether the authorized or qualified employee verifies effective isolation and de-energization depends upon the energy source. For example, an electric disconnect switch may control a mechanical or an electrical energy hazard, or both, depending on the electrical system design and the nature of the work tasks involved.

With respect to employees working on or near de-energized electrical utilization systems (covered by Subpart S, Electrical, standards), both the authorized employee and the qualified employee are permitted to verify that electrical equipment has been de-energized. However, the authorized employee would need to meet and be trained on all qualified employee requirements in 1910.331 through 1910.335 and 1910.399.

The verification of isolation for mechanical hazardous energy, on the other hand, is addressed by paragraph 1910.147(d)(6). The authorized employee(s) must, prior to the start of work, verify that the previous steps of the energy control procedure have effectively isolated the machine or equipment. These steps must include verification that the machine or equipment has been turned off properly; that all energy isolating devices were identified, located, and operated; that the lockout or tagout devices (or application of a lock and tag for electrical control purposes) have been attached to energy isolating devices; and that stored energy has been released, discharged, and rendered safe.

A person meeting the authorized employee and/or qualified employee requirements must, prior to the start of work, ensure that the previous steps of the energy control procedure have been taken to isolate the machine or equipment effectively. In some cases, verification may involve a deliberate attempt to start up the machine or equipment which should not be capable of energization or activation due to the application of locks and/or tags to the energy control devices.

Other appropriate means of hazardous energy verification may include visual inspection techniques (e.g., visually checking that safety blocks are in place in accordance with the energy control procedure; visually checking a pipe "sight glass" for the absence of a fluid) or testing the machine or equipment with an appropriate test instrument (e.g., voltmeter; combustible gas/oxygen indicator.) One key difference between the electrical verification process and the verification process in 1910.147(d)(6) is the mandated use of electrical test equipment, under 1910.333(b)(2)(iv)(B), to verify that the circuits and electrical parts of the equipment are de-energized.

Question 2: Does it matter who employs the individual who is assigned to shutdown the equipment and to verify isolation and de-energization?

Reply: No. Any affected or authorized person may shut down a machine or piece of equipment, as long as that person follows the procedures established for shutting down the machine or piece of equipment in accordance to 1910.147(d)(2). Prior to the time that the authorized employee(s) start to work on a machine or a piece of equipment that has been locked out or tagged out, the authorized employee(s) must verify isolation and de-energization of the machine or the piece of equipment. While isolation and de-energization may be accomplished by a single authorized employee (a "primary authorized employee") in a group lockout/tagout scenario, each authorized employee has the right to participate in the verification process, if he/she chooses to do so. For additional guidance, please refer to the attached November 16, 1999 letter on the subject to Environmental Management and Training Systems, Inc.

Question 3: Do we have to employ (or train) our own representative for this phase of the lockout procedure?

Reply: You are not required to employ or train your own representative to shut down the equipment if the host employer has assigned an employee to shut down the equipment and that employee follows the established shutdown procedure. However, you are required to train each authorized employee in the recognition of applicable hazardous energy sources, the type and magnitude of the energy available in the workplace, and the methods and means necessary for energy isolation and control as described in 1910.147(c)(7)(i)(A).

Question 4: Since we are not authorized to initiate the shutdown, and are only authorized to work on the equipment once it is shutdown, shouldn't we be considered "affected employees"? The term "authorized employee" implies authority and expertise that we do not have, yet we are qualified to retool or otherwise perform work on the shutdown piece of equipment.

Reply: In the situation you describe, your employees are considered "authorized employees" pursuant to 1910.147. An "affected employee" becomes an "authorized employee" when that employee's duties include the performance of servicing or maintenance as defined under 1910.147(b). The duties of your employees include servicing or maintenance activities.

In addition, you want to know what your responsibilities are to ensure that the host employer's energy control procedures effectively protect your employees. When employees are working on machines or equipment in which the uncontrolled hazardous energy could cause injury to employees, both the host employer and the contractor employer have independent obligations to provide the protection under the standard for their respective employees.

OSHA recognizes that the host employer often will have greater familiarity with the energy control procedures used at the host facility; however, contract employers may have their own procedures for protecting their employees from hazardous energy. Thus, at 29 CFR 1910.147(f)(2)(i), the standard requires the host employer and contract employer to inform each other about their respective lockout or tagout procedures. Such coordination is necessary to ensure that both sets of employees will be protected from hazardous energy.

A contractor employer would not be obligated under the OSH Act to independently audit the host employer's energy control procedures. However, the contractor employer must take reasonable steps consistent with its authority to protect its employees if the contractor knows, or has reason to know, that the host employer's energy control procedures are deficient or otherwise insufficient to provide the requisite protection to its employees.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. 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 http://www.osha.gov. If you have any further questions, please feel free to contact the Office of General Industry Compliance Assistance at (202) 693-1850.


Richard E. Fairfax, Director
Directorate of Compliance Programs

Footnote(1) Lockout and tagging procedures that comply with paragraphs (c) through (f) of §1910.147 constitute compliance with §1910.333(b)(2), as long as the procedures address the electrical safety hazards covered by Subpart S and incorporate the requirements of §1910.333(b)(2)(iii)(D) and (iv)(B). [back to text]

Footnote(2) Although the scenario is only part of a comprehensive energy control procedure, it is important to note that at least one key step is missing in this procedure. It is critical for each authorized employee to attach his or her personal lockout or tagout device on the group lockbox mechanism prior to the verification step, and before starting work, so as to maintain the lockout control of each energy isolating device. See the attached letter for details. [back to text]

Footnote(3) The concept of zero energy state is not used in 1910.147 as this OSHA standard addresses the hazard via the adoption and utilization of a complete program for the control of hazardous energy. If the energy source does not have the capability of causing injury to employees, it is not hazardous energy within the scope of the lockout/tagout standard. [back to text]

Standard Interpretations - Table of Contents

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