How must emergency stop buttons be marked?

According to 1910.144(a)(1)(iii), emergency stop buttons or electrical switches on which letters or other markings appear, used for emergency stopping of machinery, must be red.

According to 1910.66, Appendix D, emergency stop buttons must also be marked “STOP.”

OSHA does not require the use of “PUSH” labels on emergency stop button notifications.

The OSHA regulations do not specifically address the color of the backing of the emergency stop controls. However, industry standard NFPA 79, “Electrical Standard for Industrial Machinery,” specifies the backing should be yellow.

OSHA has referenced NFPA 79 when issuing General Duty Clause citations for emergency stop control design. In fact, the following is from an April 1, 2010, General Duty Clause citation:

“Section 5(a)(1) of the Occupational Safety and Health Act of 1970: The employer did not furnish employment and a place of employment which were free from recognized hazards that were causing or likely to cause death or serious physical harm to employees in that employees were exposed to caught-in/laceration hazards...The equipment emergency stop controls were not readily accessible and in some cases, not easily identifiable. The emergency stop controls had shrouds/guards around the buttons and the background immediately around the pushbuttons was not colored yellow. A feasible and acceptable abatement would be to ensure ... that the background immediately around the pushbuttons is colored yellow, in compliance with industry recognized guidelines for the design and installation of emergency stop devices, such as but not limited to: American National Standard Institute (ANSI) B11.18-2006 Safety Requirements for Machines Processing or Slitting Coiled or Non-Coiled Metal, Sub Clause 6.3.4.4; American National Standards Institute (ANSI) B11.20 Safety Requirements for Integrated Manufacturing Systems; National Fire Protection Association (NFPA) 79 Electrical Standard for Industrial Machinery, Section 10.7 ...” [emphasis added]