Which device prevents tailgating by requiring two interlocking doors?

• A. Turnstile
• B. Mantrap
• C. Elevator with credential
• D. Blast barrier

Answer: (B)

The key idea is stopping someone from slipping in behind another person by controlling entry with two doors that cannot be open at the same time. A mantrap creates a small, enclosed space with two interlocking doors. You present credentials and enter through the first door, which then locks behind you. Only after your identity is verified does the second door open, allowing you into the secured area. This setup ensures that each person is individually authenticated and prevents tailgaters because there isn’t a moment when the second door is open while a second person can rush in behind the first.

Turnstiles can limit one person at a time, but they don’t inherently require two interlocking doors. An elevator with a credential simply gates access to the elevator car, not a two-door interlock. A blast barrier is about stopping blasts, not controlling entry via interlocking doors.