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.

March 22, 2000

Mr. John D. Weagraff, CSP
Safety Futures
60 Olde Maple Avenue
Fulton, NY 13069

Dear Mr. Weagraff:

Thank you for your November 12, 1999 letter to the Occupational Safety and Health Administration's (OSHA's) [Directorate of Enforcement Programs]. You have a question regarding acceptable work practices associated with the Control of Hazardous Energy Source (Lockout/Tagout) standard, 29 CFR §1910.147. Your scenario, questions, and our reply follow:

Scenario: Specific types of heating, ventilation, and air conditioning units (heat pumps) are located in overhead areas of office spaces. A preventive maintenance (PM) operation necessitates the equipment to be de-energized for employee protection. A single source of energy is controlled by one single disconnect switch located less than ten feet away from the heat pump unit, within the ceiling area.
1 The disconnect is considered to be under the exclusive control of the maintenance technician. The disconnect access by other employees can only occur if someone were to climb to the elevated position (via ladder) while the technician was engaged in the PM operation.

This scenario is uniquely similar to the §1910.269(m)(2)(iii) single crew requirements involving an accessible and visible disconnection means that is under the sole control of the employee in charge of the clearance.

Question 1: For the operation described above, can the disconnect be considered an exception, similar to that which is described in §1910.147(a)(2)(iii)(A)?

Reply: No. Based on the scenario, it is assumed the heat pump system is not cord-and-plug powered; therefore, the §1910.147(a)(2)(iii)(A) exception would not apply. In addition, we believe that the expansion of this exemption paragraph is not warranted and would require reopening the rulemaking record to revise the rule.

The §1910.269 provisions, which are referenced in your letter, do not apply to the circumstances that you have described. Section 1910.269(m) addresses the de-energizing of electric transmission and distribution lines and equipment that are significantly different from other energy systems found in general industry operations. As to your scenario involving heating, ventilation, and air conditioning units, you should note that the electrical standards (in §1910, Subpart S) contain requirements for employee safety relative to electrical utilization hazards in the workplace. The electrical safety-related work practices section contains separate lockout and tagging provisions [§1910.333(b)] in order to safeguard workers from the hazards related to contact with electrically energized parts.

Question 2: If the operation described above is not considered an exception in accordance with paragraph 1910.147(a)(2)(iii)(A), could a tagout device be used if no other additional safety measures are available to demonstrate full employee protection, and other tagout provisions of the standard are met?

Reply: No. The standard creates a preference for the use of lockout devices if the energy isolating devices are "capable of being locked out." When an energy isolating device is capable of being locked out, tagout devices may be used only if the employer can demonstrate that its tagout program provides "full employee protection," as required by §1910.147(c)(3). Additional safety measures for the tagout ("Tags Plus") are mandated, given the inherent limitations of a tag, in order to achieve a level of safety that is equivalent to that which would be achieved through a lockout system. In other words, the employer must implement additional safety measures that "bridge the gap" between the degree of safety achieved through lockout and the degree of safety achieved through tagout.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. Please be aware that the enforcement guidance contained in this response represents the views of OSHA at the time the letter was written, based on the facts of an individual case, question, or scenario. 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 wish to 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 Enforcement at (202) 693-1850].


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

[Corrected 1/17/2005]



1 In accordance with 29 CFR 1910, Subpart S, it is important to note that the electrical disconnecting means and over-current devices need to be installed at a readily accessible location. The term readily accessible, as defined in §1910.399, is "Capable of being reached quickly for operation, renewal, or inspections, without requiring those to whom ready access is requisite to climb over or remove obstacles or resort to portable ladders, chairs, etc." The ceiling-mounted electrical disconnect does not meet this installation requirement. [ Back to text ]