Providing Safety
The function of Access keys vs Safety keys

Prevent Entrapment in Hazardous
Areas with Access and Safety Keys

Entrapment in hazardous areas is a significant safety concern in many industrial settings. Accidental activation of machinery while personnel are performing maintenance or other tasks can lead to severe injuries or fatalities. Fortress Safety has developed a robust Trapped Key System, that uses access and personal safety keys, that is designed to ensure that machinery is properly shut off and remains inoperable while personnel are in potentially dangerous areas. This article explores how the use of access and safety keys can effectively prevent entrapment hazards, ensuring a safer working environment.

Using the Trapped Key System from Fortress Safety, specific actions must be performed before entering a safeguarded area. This system ensures that machinery within the secured area is properly shut off before entry, safeguarding personnel from potential hazards and entrapment.

The difference between Access and Safety Keys:

Access Keys

Access keys are used to control entry to specific areas or machinery, ensuring access is granted only when it is safe. They are inserted into locks that  control doors or gates, and only when the access key is turned can the door be opened. This mechanism ensures controlled and safe access to hazardous areas.

Safety Keys

Safety keys are to ensure your personal safety, during your presencec in a dangerous area. In systems where access to hazardous areas is restricted, personnel take these keys out of the key exchange unit after inserting the access key into the interlock. This prevents the lock from being closed during maintenance. Workers carry the safety keys into the restricted area, ensuring maximum safety by making it impossible to restart machinery until all keys are returned.

Both these keys are integral to Trapped Key Systems, like the mGard range from Fortress Safety. In a key exchange system, one key must be inserted and turned before another can be removed, enforcing a strict sequence of operations. A trapped key interlocking system ensures that actions like opening a door or starting a machine can only be performed when a key is in the correct position.

Features of Fortress Keys


Fortress Safety allows for the engraving of access and safety keys to be 30 characters spread across three lines. Additionally, keys can be fitted with a colored cover or bow, available in eight different colors, to distinguish specific keys. A seal, available in nine colors, can also encase the key for further differentiation.

We have a comprehensive article on Fortress engravings.


The Fortress keys are made from robust materials, these keys can withstand rotational forces up to 10 Newton-metres without risk of damage. This durability ensures longevity and reliable performance.

Safety Enhancement

By ensuring that machines and hazardous areas can only be accessed under safe conditions, these keys significantly reduce the risk of accidents. The Trapped Key System mandates that machinery is shut off and cannot be restarted until all personnel have exited the hazardous area and returned their safety keys.

Beveiligen van een lasrobot

Applying the Trapped Key System in Everyday Operations


Before a maintenance worker can enter a machine area, they must insert their access key into the interlock to power down the machinery. This action releases a safety key which they carry with them into the area. As long as the safety key is with the worker inside the area, the machine cannot be restarted, ensuring the worker’s safety.

Machine Guarding

In a manufacturing setting, operators might need to access guarded areas of a machine. The trapped key system ensures that the machine is stopped and remains inoperable while the guard is open, protecting operators from moving parts.

While the Trapped Key System does not physically prevent someone from being trapped, it significantly reduces the likelihood of entrapment and other accidents by ensuring that machinery cannot be operated while personnel are in hazardous areas. This enforced sequence of operations and controlled access to dangerous areas are critical for maintaining a safe working environment.

Products mentioned in this article:

Trapped Key System

The only interlock system that is TüV certified to Ple

Share this article


Latest articles

Alpha and Bravo interlock blocking devices, how do they work?

ALPHA and BRAVO are fully mechanical safety systems that regulate access to safeguarded areas. Both systems are designed to increase…

Fortress Key Engravings

Trapped Key Systems are advanced safety devices commonly used in manufacturing plants...

Connect with USP

Direct contact

The Netherlands
Van ’t Hoffstraat 4
2665 JL Bleiswijk
The Netherlands

+31 (0)10 – 8224400

Theodorstraße 105
40472 Düsseldorf

+49 (0)211 – 302 979 18

Related articles