Flammable materials include gases and volatile liquids that could be formed into a vapor cloud and ignited to cause a fire or detonation. They are in common use across the United States for fuel, industrial feedstocks, and a variety of other applications and could be released from production, storage, or transport facilities.

As with industrial chemicals, the distribution systems for explosives and flammable agents are vulnerable to attack. These systems include trucking and shipping networks (especially liquefied natural gas tankers and their shore facilities), railroad lines, pipelines that carry natural gas or other gaseous or liquid hydrocarbons, and underground sewers or utility tunnels. These systems are all susceptible to hijacking and use of explosive or flammable materials as weapons, or to physical damage, with consequent disruption of service. In some cases, injuries and environmental damage may occur near where a pipeline is breeched.

Underground sewers or utility tunnels could be used as conduits for releasing toxic, flammable, or explosive materials. Chemicals could disperse through these systems and eventually emerge from manholes, drains, and other openings, or they could ignite or explode under streets and near buildings (see Chapter 8). Another potential dispersal mechanism is a subway system. Materials in the subway tunnels could be “pumped” through the city by the trains—a particularly effective method for delivering powderized materials like anthrax, but it might also work for spreading chemical agents.


Sensors and Operational Systems for Detecting and Characterizing Chemical Agents

Improved and expanded use of sensors must play a major role in preventing catastrophic terrorism or, if attacks do occur, in minimizing their impacts. Sensors have the potential to thwart terrorist activities in the planning stage, or before or during attempted attacks, and to help identify individuals with malicious intent. They may also be useful in forensic analysis to identify perpetrators after an attack.

Possible applications include the following:

  • Improved sensors to detect explosives in luggage and enhance airport security (see Box 4.1 and Chapter 7);

  • Sensors to help provide sensitive and rapid warning for the protection of fixed sites (subways, airports, government buildings, financial centers, high-value industries). For example, sensors for ventilation systems capable of detecting deviations from normal conditions and monitoring for chemical and biological agents could be coupled to rapid-shutdown procedures, especially at the final vent (see Chapter 8);

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