Descent Access Gate

A Descent Access Gate (DAG) is a high-security checkpoint that forms the boundary between the low-security Topside and the high-security Descent section of Black Mountain. There are a total of 12 + 4 DAGs, for a total of 16: 12 personnel DAGs and 4 cargo DAGs. Each personnel DAG has 1-4 lanes on average. A lane is a set of two hermetically-sealed blast doors set up in an airlock configuration both to prevent tailgating and to ensure the integrity of the Descent biosphere. In the middle of each airlock is a personnel scanner configured to detect biohazards, radiation, weapons, and other types of contraband.

All movement through DAGs must be scheduled in advance with Internal Security. Except for those in positions with a need to travel Topside frequently, Descent residents are only permitted Topside during scheduled holiday periods, where they must be constantly escorted.

Location

DAGs are located close to the surface level and not close to the bunker level; the rationale is that personnel should be authorised before they take the descent. An elevator connects the inside of each DAG checkpoint down to the bunker. Like the bunker itself, the elevator shafts are protected by forcefields, and they also additionally incorporate automatically closing doors between sections of the shaft to prevent their entire height from being exposed at once.