Ten Dangerous Scenarios

Attack a nuclear plant

Cripple the
Transportation System

Destroy the
Fort Peck Dam

Detonate a suitcase bomb

Attack the Alaska pipeline

Contaminate a ventilation system

Cut off power to
a major city

Shoot down
Air Force One

Attack a chemical factory

Destroy a stadium

>> See the entire list <<

Scenario: Release a chemical or biological agent into a building ventilation system

Scenario

Release a chemical or biological agent in a building ventilation system through an intake duct and contaminate the entire building.

Description

Large commercial buildings have sophisticated ventilation systems. They recirculate air inside the building, and also take in fresh air from the outside. A terrorist could release a biological or chemical agent into either an interior or exterior air intake and contaminate the entire building.

During the 2001 anthrax event, the terrorist involved actually took advantage of this effect inadvertently. When the anthrax letter sent to Tom Daschle was opened, anthrax spores from the letter were distributed through the ventilation system to other parts of the Hart senate office building. Cleanup costs exceeded $10 million to decontaminate the building.

In most buildings, interior air intakes are easily accessible to anyone in offices or hallways. In many buildings, exterior air intakes are at ground level and are not secure. When air intakes are on the roof, they are often not secured. If they are, a terrorist can often gain easy access by posing as maintenance personnel.

Potential biological or chemical agents include things like anthrax as well as any chemical from chlorine gas to nerve agents like Sarin.

A large chemical or biological attack on a city would likely result in the contamination of all the buildings in the city through their ventilation systems.

Damage Potential

The damage would come from the death of, potentially, everyone in the building. A large building can house thousands of people. If the building holds the key personnel of a major corporation or government facility, the loss of life could potentially decapitate that organization. For example, a chemical attack on the headquarters of a corporation like Microsoft could potentially delay a number of important projects.

Potential Solutions

Radio Controlled Attack

As described in this scenario, R/C aircraft have become quite sophisticated in recent years. One way to attack a building's ventiation system would be to load a R/C airplane with 5 pounds of anthrax spores or Sarin and crash the plane right into the ventilation intake on the roof of the building.

One way to block this threat would be to place sensors at the air intakes that detect explosions or impact and shut down the air handlers immediately.

We know that there are quantities of high quality anthrax spores in the hands of terrorists in the United States. We know that terrorists in Tokyo have successfully manufactured and released Sarin. We know that small quantities of either substance are sufficient to contaminate an entire building. This scenario is far from abstract.

  • Following September 11, one proposal called for the creation of buildings that are immune to biological and chemical attack, and also immune to a biological or chemical attack on a city. In this proposal, all air introduced into the building first ran through what was, in essence, an incinerator. High heat would kill any biological agent and decompose any chemical agent in the air. The incoming air would create positive pressure inside the building and keep out contaminants. No air inside the building would be recirculated. If a city were attacked, buildings like these would act like "bomb shelters" to protect people from the biological or chemical agents in the air.
  • Securing all exterior air intakes is an obvious step.
  • Tighter security on air handlers and maintenance personnel.
  • Protecting interior air intakes is harder unless the system is designed with chemical and biological threats in mind. One approach is to vent all return air (collected through air intakes inside the building) outside through a heat exchanger, and replace it with fresh outside air. Another approach involves filtration and/or decontamination, but that will not protect against a chemical attack.
  • You can also protect interior air by screening everyone who enters the building. However, it is easy to conceal some chemical and biological agents because the required amounts are so small.

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