To be effective, a safeguarding device such as interlocked gates, 2 hand controls, safety mats, lights curtains and laser scanners must either stop or prevent the start of hazardous motion.

Machinery must stop in the time it takes a person to open the guard, break a light beam or activate a stop and reach the hazard.

Safety devices will be in-effective if the distance to the hazard is too short and the person can reach the danger point before the hazard can be controlled. In such circumstances additional risk is created as the person is given a false sense of safety.

The distance between activation of the safety device and the stopping time of the machine is known as the "Safety Distance".

BS EN ISO 13855 is an International Standard which establishes the positioning of safeguards with respect to the approach speeds of parts of the human body. It specifies parameters based on values for approach speeds of parts of the human body and provides a methodology to determine the minimum distances to a hazard zone from the detection zone or from actuating devices of safeguards. Calculated from the formula ISO EN: S = K × T + C. The value of T = the overall system stopping performance can be measured by undertaking a "Stop time test".

The stop time test service provided by ISS Safety is undertaken by experienced safety engineers using modern test equipment to measures stop time, stop distance and velocity of power driven machinery like presses, shears, welders, riveters and robots. The resulting data can be used to confirm the current position of existing safety devices, the selection of the correct safety technology or the correct positioning of new safety devices.

A stop time test certificate is provided for each machine tested. The data can be used for compliance verification and validation purposes and inclusion within the Technical File for CE Mark applications.