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Standard Interpretations - Table of Contents
• Standard Number: 1910.147; 1910.147(c)(5); 1910.333

July 8, 2002

Name Withheld

To whom it may concern:

Thank you for your letter to the Occupational Safety and Health Administration’s (OSHA’s) Directorate of Compliance Programs regarding the Control of hazardous energy (lockout/tagout), 29 CFR 1910.147, standard. This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any scenario not delineated within your original correspondence. Your scenario, questions, and our replies follow.

Scenario: Operations personnel clear and isolate process equipment using lockout to secure the energy isolating devices. For each energy source, this consists of a lock secured to an energy-isolating device. The key to each lock is then secured in a lockbox.

Additionally, as part of the energy control procedure, the maintenance group will verify the lockout and hang a tag on each lockout device as part of this verification process.
(1) Each person working on the job will then affix a personal lock onto the lockbox.

Question 1: Is this verification tag a tagout device?

Reply: No. A tagout device is defined in 29 CFR 1910.147 as:
A prominent warning device, such as a tag and a means of attachment, which can be securely fastened to an energy isolating device in accordance with an established procedure, to indicate that the energy isolating device and the equipment (or machine) being controlled may not be operated until the tagout device is removed.
The described verification tag does not meet the definitional requirements for a tagout device as its purpose is to simply indicate that isolation or de-energization of the machine or equipment has been effectively accomplished. It appears that your primary means of energy control are lockout devices, which, in your scenario, positively secure the energy isolating devices in a safe position.

Question 2: What is an acceptable manner for the maintenance group to affix their tags to the lockout devices as part of their verification of the lockout?
(2) (3)

Reply: The standard does not require that tags be used to verify isolation or de-energization of machinery or equipment. However, if your energy control procedure contemplates the use of tags to assist in the verification process, it would be important for the tags to be constructed and affixed in a manner that would allow them to remain in place until the verification process is complete. A high quality tag and means of attachment would then enable the verification tags to be used as described in the company energy control procedure. If the tags were too flimsy and regularly were destroyed or misplaced after placement, an authorized employee, aware of this ongoing problem, might incorrectly assume that verification occurred when in fact it did not.

Question 3: Would a verification tag with a reusable means of attachment be permitted?

Reply: Yes.

Question 4: Does the verification tag need to meet the 1910.147(c)(5) protective materials and hardware specification requirements?

Reply: No, 1910.147(c)(5) applies only to materials and hardware used for isolating, securing, or blocking machines or equipment from energy sources. In your scenario, lockout devices are used to secure the energy isolation devices. Thus, paragraph (c)(5) would not apply to the verification tags that you have described.

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 ny further questions, please feel free to contact the [Office of General Industry Enforcement] at (202) 693-1850.


Richard E. Fairfax, Director
Directorate of Compliance Programs


(1) This verification step must ensure that the previous steps of the procedure have been taken to safely isolate the machine or equipment effectively. This procedural step may need to include visual checks, machine start-up attempts, and/or actual testing (e.g., use of a combustible gas meter or voltmeter by a qualified employee) to determine that the isolation has been accomplished. [ back to text ]

(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- or tagged-out, each authorized employee(s) must verify isolation and de-energization of the machine or the piece of equipment. OSHA has recognized an alternative to the verification requirements where complex lockout/tagout operations exist. In such situations, the employer may designate a “primary authorized employee” to coordinate and implement the verification of isolation process. However, each authorized employee has the right -- and must be given the opportunity -- 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. [ back to text ]

(3) It should be noted that paragraph (b) of 1910.333 covers work on or near exposed de-energized electric parts and includes requirements for lockout and tagging of equipment disconnecting means. The requirements for electrical lockout and tagout procedures, although similar in some aspects, are distinct from the 1910.147 lockout/tagout provisions. [ back to text ]
Standard Interpretations - Table of Contents

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