Glossary: Guard locking vs. interlocking

07.05.2025

EN ISO 14119 defines two important safety functions: Interlocking and guard locking. But what is the difference – and when do you need which?

Interlocking

An interlocking device puts a machine or system into a safe state as soon as a safety gate is opened. It prevents access to hazardous points in and on these machines.

For example: When a safety gate is opened, the interlocking device immediately puts the machine into a safe state. There are no residual hazards such as stored energy or long overtravel movements.

Guard locking

A guard locking device goes one step further. It not only prevents the machine from starting when the door is open, but also actively keeps the door closed as long as there is a hazard – even if an operator tries to open it. This is particularly necessary for machines with long stopping times or high kinetic energy.

When do I need what?

An interlock is sufficient if there is no residual danger after the safety guard has been opened. After opening or passing through the safety guard, there is no longer any potential danger for the person.
Guard locking is required when dangerous movements or stored energy remain after opening, e.g. on large presses or rotating machines with long overtravel.

The right choice of protective measures in accordance with EN ISO 14119 is essential to ensure safety and productivity. If you are unsure, we recommend a professional risk assessment.