Security Vestibule : A compartment provided with two or more doors where the intended purpose is to prevent continuous and unobstructed passage by allowing the release of only one door at a time
NFPA 1221 Standard for the Installation, Maintenance, and Use of Emergency Services Communications Systems, 2007 ed. (Std: Install, Maint, and Use of Emr Srvc Commun - Amer) {391 NFC}