Glossary · Stopping functions and safe states
Emergency stop
Also known as: E-stop, emergency-stop function
German: Not-Halt
In machine safety, an emergency stop is a complementary protective function intended to avert or reduce existing or impending hazards by stopping hazardous operation. It is initiated by a single human action and is not a substitute for safeguards or other protective measures.
- Machine safety
- EU
- Technical documentation
In one sentence
The emergency stop is a complementary protective function that stops hazardous operation by a single human action, in stop category 0 or 1.
Example
On a packaging line, red mushroom-head buttons on a yellow background at each operator station stop all hazardous motion of the line in stop category 1; restarting requires resetting the button and a separate start command.
How it applies
- Machine safety: The emergency stop function must work as stop category 0 or stop category 1, be available in every operating mode and take precedence over other functions. It supplements safeguards; it does not replace them.
- Reset and restart: Actuators latch when operated. Releasing the actuator must not restart the machine; restart needs a deliberate manual reset and a separate start command.
- Technical documentation: The manual states where the emergency stop devices are, what they stop (the whole line or one zone), how to reset them and how often to test them. Do not present the emergency stop as a means for normal stopping or for securing a machine before maintenance.
- Evidence: The emergency stop is a safety function in its own right, so its required performance and validation belong in the evidence file.
Emergency stop vs. emergency switching off
An emergency stop stops hazardous motion or processes. Emergency switching off removes electrical energy where electrical hazards such as electric shock are involved. They address different hazards and are covered by different requirements: the emergency stop by ISO 13850 and IEC 60204-1, emergency switching off by IEC 60204-1. Neither is a substitute for lockout/tagout.