Door Interlock

There are many applications that require the prevention of the free flow in or out of the secured area by unauthorised personnel or other beings such as livestock when an access door is unlocked. An interlocking door system provides an ideal solution to this problem.

Door Interlock solution diagram

An interlocking door system uses a ‘vestibule’ between the secured area and the unsecured area, with a lockable door between each area and the vestibule.

The locking system is arranged in such a way that, while one door is open, the opposite door cannot be unlocked. This arrangement is sometimes referred to as an ‘air lock’. An authorised person must pass through one door and close it behind them before they can unlock the second door. If an unauthorised person were able to force their way into the vestibule while the door is unlocked, they would be unable to progress any further until an authorised person unlocks the second door.

It may be necessary to prevent the possibility of an authorised person being accompanied by an unauthorised person when they pass through the air lock. In this case, the system may be enhanced by adding a sensor/detection device within the vestibule to ensure that there is only one person within the vestibule before the second door can be unlocked. Examples of detection devices are optical or body heat sensing devices and weight sensors.


  • Storage of high value items
  • Storage of delicate antiquities
  • Research and Development Centres
  • Laboratories and equipment rooms requiring positive air pressure
  • Climate controlled areas
  • Zoos
  • Animal husbandry


  • Increased security without the need for expensive equipment
  • Reduces the risk of loss or damage to property through oversight
  • Reduces the danger of death or injury through oversight

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