6.6 Chemical, Biological, and Radiological Protection

This section discusses three types of air-borne hazards.

1. A large exterior release originating some distance away from the building (includes delivery by aircraft).
2. A small localized exterior release at an air intake or other opening in the exterior envelope of the building.
3. A small interior release in a publicly accessible area, a major egress route, or other vulnerable area (e.g., lobby, mail room, delivery receiving).

Like explosive threats, chemical, biological and radiological (CBR) threats may be delivered externally or internally to the building. External ground-based threats may be released at a standoff distance from the building or may be delivered directly through an air intake or other opening. Interior threats may be delivered to accessible areas such as the lobby, mailroom, or loading dock, or they may be released into a secured area such as a primary egress route. This discussion is limited to air-borne hazards.

There may not be an official or obvious warning prior to a CBR event. While you should always follow any official warnings, the best defense is to be alert to signs of a release occurring near you. The air may be contaminated if you see a suspicious cloud or smoke near ground level, hear an air blast, smell strange odors, see birds or other small animals dying, or hear of more than one person complaining of eye, throat or skin irritation or convulsing.

Chemicals will typically cause problems within in seconds or minutes after exposure, but they can sometimes have delayed effects that will not appear for hours or days. Symptoms may include blurred or dimmed vision; eye, throat, or skin irritation; difficulty breathing; excess saliva; or nausea.

Biological and some radioactive contaminants typically will take days to weeks before symptoms appear, so listen for official information regarding symptoms.

With radioactive “dirty” bombs, the initial risk is from the explosion. Local responders may advise you to either shelter-in-place or evacuate. After the initial debris falls to the ground, leaving the area and washing will minimize your risk from the radiation.

Buildings provide a limited level of inherent protection against CBR threats. To some extent, the protection level is a function of how airtight the building is, but to a greater extent it is a function of the HVAC system’s design and operating parameters.

The objectives of protective building design as they relate to the CBR threat are first to make it difficult for the terrorist to successfully execute a CBR attack and second, to minimize the impact (e.g., life, health, property damage, loss of commerce) of an attack if it does occur.

In order to reduce the likelihood of an attack, use security and design features that limit the terrorist’s ability to approach the building and successfully release the CBR contaminant. Some examples are listed below.

• Use security stand-off, accessibility, and screening procedures similar to those identified in the explosive threat mitigation sections of this document (see Chapter 5, Design Approach and Section 6.1, Site Location and Layout).
• Recognize areas around HVAC equipment and other mechanical systems to be vulnerable areas requiring special security considerations.
• Locate outdoor air intakes high above ground level and at inaccessible locations.
• Prevent unauthorized access to all mechanical areas and equipment.
• Avoid the use of ground-level mechanical rooms accessible from outside the building. Where such room placement is unavoidable, doors and air vents leading to these rooms should be treated as  vulnerable locations and appropriately secured.
• Treat operable, ground-level windows as a vulnerability and either avoid their use or provide appropriate security precautions to minimize the vulnerability.
• Interior to the building, minimize public access to HVAC return-air systems.

Further discussion of some of these prevention methods is provided below.