Full definition
A safety device that brings machinery to a safe stop as quickly as possible when activated by a worker in response to a hazardous situation. The emergency stop function is a complementary safety measure — it does not replace primary safeguards (guards, interlocks) but provides an additional layer of protection. Per IEC 60204-1 (electrical safety of machinery) and ISO 13850: the actuator must be red colored on a yellow background for instant visual identification, easily accessible without reaching into danger zones, and designed for positive opening (direct mechanical actuation, not dependent on electronics). Types: (1) Mushroom-head push button (most common — latching type, requires deliberate manual reset). (2) Pull-cord/cable (for long machines like conveyors — worker pulls wire from any point along the machine). (3) Foot-operated treadle (for presses and machine tools). (4) Pressure-sensitive edge/mat (detects contact/presence). Stop categories per IEC 60204-1: Category 0 (immediate power removal — hardwired), Category 1 (controlled stop then power removal), Category 2 (controlled stop, power maintained for braking). Emergency stop circuits must be hardwired (not software-dependent) and monitored by safety relays per ISO 13849 (SIL/PL rating). Per NOM-004-STPS (Mexico), OSHA 29 CFR 1910.212, and IEC 60204-1.