Explanation
An access control vestibule, also known as a mantrap, is a physical security access control system that consists of a small space with two sets of interlocking doors. The first set of doors must close before the second set opens, preventing unauthorized individuals from following authorized individuals into facilities with controlled access. This activity, also known as tailgating, results in unauthorized access to the facility. An access control vestibule can help deter and detect tailgating attempts, as well as provide a containment area while authorization for physical access is verified.
References
Access Control Vestibules: Types and Peculiarities
Mantrap (access control)
PE-3 (8): Access Control Vestibules