Whether in the workplace or for the general public, emergency stop switches are a fail-safe device to ensure a person and/or machine safety. There are U. S. federal regulations for an emergency stop switch.
The U.S. Department of Labor, Occupational Safety and Health Standards, defines an emergency stop switch as "a manually or automatically operated electric switch to cut off electric power independently of the regular operating controls" (Code of Federal Regulations 29 part 1910.179a,59). Go to the Department of Labor website (osha.gov). In the search box on the home page, type "29 cfr 1910." Click the button marked "OSHA" and click "Search." You will have access to the complete Code of Federal Regulation. Scroll down the page and click "179."
Once an emergency stop switch has been triggered, "the conveyor cannot be started again until the actuating stop switch has been reset to running or 'on' position," according to the Code of Federal Regulations 29 part 1926.555a,3.
Welding Stop Button
Welding-type machines require emergency stop buttons. "Two or more safety emergency stop buttons shall be provided on all special multispot welding machines, including 2-post and 4-post weld presses," according to the Code of Federal Regulations 29 part 1910.255b,7.