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NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.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

April 11, 2000

Mr. James D. Dykes, CSP
Safety Consultation
5013 Iron Horse Trail
Colorado Springs, CO 80917

Dear Mr. Dykes:

Thank you for your January 13, 2000 letter and February 14, 2000 fax to the Occupational Safety and Health Administration's (OSHA's) [Directorate of Enforcement Programs (DEP)]. Specifically, you want to apply the exception listed under 29 CFR 1910.147(c)(4)(i) and believe that the company has met all eight of the "exceptions."

The OSHA standard 29 CFR 1910.147, The control of hazardous energy (lockout/tagout), covers the servicing and maintenance of machines and equipment in which the unexpected energization or start up of the machines or equipment, or release of stored energy could cause injury to employees. This standard established minimum performance requirements for the control of such hazardous energy.

Since the natural gas, which is used to heat the oven, poses a potential thermal energy hazard for employees who are performing maintenance or servicing activities, the provisions of 29 CFR 1910.147 are applicable. Further, the exception to 29 CFR 1910.147(c)(4)(i), which provides that an employer need not document the required energy control procedure for a particular machine or equipment when eight specified conditions exist, is inapplicable to situation that you have described. Since it appears that the oven has at least two energy sources, and it is unlikely that a single lock-out device can be used to effectively lock-out the oven, at least two of the eight conditions which are essential to the application of the exception are not met.

29 CFR 1910.147(b) defines "energy source" as, any source of electrical, mechanical, hydraulic, pneumatic, chemical, thermal, or other energy. Since the natural gas is used to heat the oven, it is an energy source. Since natural gas, if unexpectedly released and ignited, would produce potentially hazardous thermal energy, an energy control procedure, consistent with the requirements of 29 CFR 1910.147(c)(4)(i) is required to address the potential hazards associated with the natural gas.

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 6/2/2005]