How Interlocking Doors Work

Rob Suddaby
Posted by Rob Suddaby
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An interlocking door is one of the most secure methods of access control available to site security managers. But how exactly does it work?

In its simplest form, an interlocking system is composed of two doors electronically connected so one cannot open until the other has closed.




Using identification, you enter the first door which must close behind you before the second door opens and allows you to pass through. Rather like an airlock.

High-Level Entrance Security

Interlocking doors provide one of the highest levels of entrance control and access management available.

As well as intrusion protection, they can also offer first-class physical protection with resistance against ballistic and blast attacks. 

Detection and Identification Systems

Interlocking doors are often fitted with a range of different detection systems. Single person sensors, for example, detect when more than one person has entered into the booth and prevents the second door from opening.

It is also common for metal detectors to be built into a booth when there is a threat of firearms being carried through.

Aside from standard identification methods, such as cards and PIN codes, biometric readers that recognise faces, retinas or fingerprints add a further level of security to an interlocking door.

Piggybacking and Tailgating

Interlocking doors are particularly effective at stopping piggybacking or tailgating.

Piggybacking and tailgating are attempts to enter a restricted area by following closely behind someone with the correct authorisation. 




The subtle difference is consent:

  • Tailgating is following an authorised person without their consent
  • Piggybacking refers to the same practice, but the authorised person is in on the act

Read more about how interlocking doors are used to maintain high security levels and restrict the movement of unauthorised individuals around a site.

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