A mantrap is a small room with an entry door on one wall and an exit door on the opposite wall. One door of a mantrap cannot be unlocked and opened until the opposite door has been closed and locked.
Mantraps are most often used in physical security to separate non-secure areas from secure areas and prevent unauthorized access. They can also be found in high tech manufacturing to provide entry and exit chambers for clean rooms.
In the Middle Ages, mantraps were used to check visitor credentials in prisons. A visitor would be allowed entry into an enclosed vestibule, at which time the entry door would be locked and the visitor’s credentials examined. If the credentials didn’t check out -- or if the visitor was determined to be a person of interest – the trapped visitor could easily be arrested.
Today’s mantraps use interlocking doors that are interfaced so that when one door is unlocked, the other door automatically locks. Pass-through authorization is validated by smart card, key fob or biometric verification. Some systems may employ three-dimensional optical imaging or thermal imaging technology to prevent more than one person from passing through a mantrap at the same time.
This video shows a mantrap denying access to an employee until both doors are closed and locked.