6.6.4 Lobbies, Loading Docks, and Mail Sorting Areas

Vulnerable internal areas where airborne hazards may be brought into the building should be strategically located. These include lobbies, loading docks, and mail sorting areas. Where possible, place these functions outside of the footprint of the main building. When incorporated into the main building, these areas should be physically separated from other areas by floor-to-roof walls. Additionally, these areas should be maintained under negative pressure relative to the rest of the building, but at positive-to-neutral pressure relative to the outdoors. To assist in maintaining the desired pressure relationship, necessary openings (doors, windows, etc.) between secure and vulnerable areas should be equipped with sealing windows and doors, and wall openings due to ductwork, utilities, and other penetrations should be sealed. Where entries into vulnerable areas are frequent, the use of airlocks or vestibules may be necessary to maintain the desired pressure differentials.

Ductwork that travels through vulnerable areas should be sealed. Ideally, these areas should have separate air-handling units to isolate the hazard. Alternatively, the conditioned air supply to these areas may come from a central unit as long as exhaust/return air from these areas is not allowed to mix into other portions of the building. In addition, emergency exhaust fans that can be activated upon internal CBR release within the vulnerable area will help to purge the hazard from the building and minimize its migration into other areas. Care must be taken that the discharge point for the exhaust system is not co-located with expected egress routes. Consideration should also be given to filtering this exhaust with High Efficiency Particulate Air (HEPA) filtration. For entrance lobbies that contain a security screening location, it is recommended that an airlock or vestibule be provided between the secured and unsecured areas.