Chapter 3.4
Guard locking
In this chapter we will explain why having the appropriate guard lock on machine guarding doors is essential to achieve optimal safety and ensure the safety of workers. If machinery needs time to stop after the opening of a guard, use electro-mechanical locks to prevent opening until any movement has stopped.
Dealing with locking-in hazards
When doors and gates in the guard fencing around a machinery system are locked during operation, this results in a secondary risk which is easily overlooked.
This can pose significant risk to the person attending to a maintenance or fault issue within the machine who can easily be locked inside. That is bad enough but imagine a colleague outside would not notice them and restart the machine. This might result in a very dangerous situation. In such case, an escape release lock is necessary to allow the person inside the door to escape and stop the machine from continuing to run.
The escape release is triggered by hitting a button or pressing down a door handle on the inside of the door. It will then open, and the machine is stopped immediately. Of course, it must not be possible to use the escape release from outside the protected area, to prevent misuse. From outside a door lock can be released by resetting the safety circuit or by an emergency release, which is standard on most guard locking switches.
Emergency release is achieved by using a special tool to forcibly open the guard locking switch. Of course, this will also stop the machine immediately.

When should escape release locks be installed?
Escape release should be installed when several or all of the following conditions are present:
- The doors are equipped with guard locking switches
- The doors could close accidentally
- The hazard zone is big enough for one or more people to stay inside
- People in the hazard zone may be hidden from view, behind a large control cabinet, machinery etc.
