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 https://www.osha.gov.


April 28, 1999

Mr. John F. Podojil, CHCM, CHMM, REP
Podojil & Associates
32422 50th Place, SW
Federal Way, WA 98023

Dear Mr. Podojil:

This is in response to your letter of December 22, 1998, requesting an interpretation on the Occupational Safety and Health Administration's (OSHA) standards regarding undervoltage protection on metal-working equipment that would prevent the machine from automatically restarting after power failure. You also requested a determination as to the types of emergency stop controls which are acceptable to OSHA.

for clarity, this letter addresses each issue separately.

Question 1: Is undervoltage protection required on metal-working equipment?

Response 1: There are no OSHA standards designed specifically to cover metal sawing machines. However, many of OSHA's standards for general industry are applicable to all types of machinery, including metal-working equipment. 29 CFR Part 1910 Subpart S — Electrical 303(b)(1) provides that "electrical equipment shall be free from recognized hazards that are likely to cause death or serious physical harm to employees." The automatic restarting of a machine after a power failure would be a recognized hazard under many circumstances. See the 1999 edition of the NEC Article 430-43, which states:


A motor overload device that can restart a motor automatically after overload tripping shall not be installed if automatic restarting of the motor can result in injury to persons.



Properly-designed and maintained undervoltage equipment that will prevent restarting would enable an employer to control this particular hazard.

Question 2: Does an emergency stop have to be of the mushroomed head type or palm button or does your agency allow other types of designs that serve the same purpose like emergency pull cords that one could find on pyramid rolls and calendars?

Response 2: Except for a few standards, such as 1910.216(b), Mills and Calendars in the Rubber and Plastic Industries, OSHA does not specifically allow or disallow certain designs of emergency stop devices. It is well recognized, however, that emergency stop devices must be properly-designed and installed so as to avoid exposing the operator or any other person to hazards while activating the stop. See the American National Standard's Institute (ANSI) B11.10, Metal Sawing Machines — Safety Requirements for the Construction, Care, and Use.

Thus, if serious injury could result from an improperly-designed or installed emergency stop device, a citation under the OSH Act's General Duty Clause could be issued. Therefore, the types of emergency stop actuators that may be used will depend on factors such as, but not limited to, the type of equipment, its application, and any additional operator safety concerns. In other words, it must be evaluated on a case-by-case basis.

if we can be of further assistance, please contact [the Office of General Industry Enforcement] at 202-693-1850.


Charles N. Jeffress
Assistant Secretary

[Corrected 8/13/2007]