6.2.2 Building Interior

In terms of functional layout, unsecured areas such as the lobby, loading dock, mail room, garage, and retail areas need to be separated from the secured areas of the building . Ideally, these unsecured areas are placed exterior to the main building or along the edges of the building. For example, a separate lobby pavilion or loading dock area outside of the main footprint of the building (see Figure 6-4) provides enhanced protection against damage and potential building collapse in the event of an explosion at these locations. Similarly, placing parking areas outside the main footprint of the building can be highly effective in reducing the vulnerability to catastrophic collapse. If it is not possible to place vulnerable  areas outside the main building footprint, they should be placed along the building exterior, and the building layout should be used to create internal “hard lines” or buffer zones. Secondary stairwells, elevator shafts, corridors, and storage areas should be located between public and secured areas.

When determining whether secured and unsecured areas are adjacent to one another, consider the layout on each floor and the relationship between floors. Secured occupied or critical areas should not be placed above or below unsecured areas.

Adequate queuing areas should be provided in front of lobby inspection stations so that visitors are not forced to stand outside during bad weather conditions or in a congested line inside a small lobby while waiting to enter the secured areas. Occupied areas or emergency functions should not be placed immediately adjacent to the lobby, but should be separated by a buffer area such as a storage area or corridor. The interior wall area and exposed structural columns in unsecured lobby areas should be minimized.

Vehicular queuing and inspection stations need to be accounted for in design of the loading docks and vehicle access points. These should be located outside the building along the curb or further away. A parking lane may be used for this purpose.

Emergency functions and elevator shafts are to be placed away from internal parking areas, loading docks and other high-risk areas. In the 1993 World Trade Center bombing incident, elevator shafts became chimneys, transmitting smoke and heat from the explosion in the basement to all levels of the building. This hindered evacuation and resulted in smoke inhalation injuries.

False ceilings, light fixtures, Venetian blinds, ductwork, air conditioners, and other nonstructural components may become flying debris in the event of an explosion. Wherever possible it is recommended that the design be simplified to limit these hazards. Placing heavy equipment such as air conditioners near the floor rather than the ceiling is one idea for limiting this hazard. Using fabric curtains or plastic vertical blinds rather than metal Venetian blinds, and using exposed ductwork as an architectural device are other ideas. Mechanically attaching light fixtures to the slab above as is done in high seismic areas is recommended.

Finally, the placement of furniture can have an effect on injury levels. Desks, conference tables, and other similar furniture should be placed as far from exterior windows facing streets as practical. Desks with computer monitors should be oriented away from the window to prevent injury due to the impact of the monitor.