Mantrap (access control)

A mantrap, air lock, sally port or access control vestibule is a physical security access control system comprising a small space with two sets of interlocking doors, such that the first set of doors must close before the second set opens.

In a manual mantrap, a guard locks and unlocks each door in sequence. An intercom and/or video camera are often used to allow the guard to control the trap from a remote location.

Airlocks have a very similar structure to mantraps but are used for the opposite purpose, allowing free ingress and egress (while also restricting airflow).

In an automatic mantrap, identification may be required for each door, sometimes even possibly different measures for each door. For example, a key may open the first door, but a personal identification number entered on a number pad opens the second. Other methods of opening doors include proximity cards or biometric devices such as fingerprint readers or iris recognition scans.

Metal detectors are often built in, in order to prevent entrance of people carrying weapons. This use is particularly frequent in banks and jewelry shops.

Fire codes require that automatic mantraps allow exit from the intermediate space while denying access to a secure space such as a data center or research lab. A manually operated mantrap may allow a guard to lock both doors, trapping a suspect between the doors for questioning or detainment.

In a lower-security variation of a mantrap, banks often locate automated teller machines within the dead space between the entrance doors and the interior lobby doors to prevent ATM robbery and night walk-up robberies. Entry access by ATM card to the dead space offers additional customer protection.