Stadiums are vulnerable to structural failure from explosives or aircraft impact; to airborne toxins; and to panic reaction by a crowd. Recent efforts to exclude explosives from sports venues and traditional efforts to exclude hazardous materials from rock concerts both illustrate apparently successful policies. There are no major recorded incidents of bomb attacks on stadiums, and the time-consuming and intrusive screening of attendees appears to be tolerated at present. There are no recorded incidents of attack by aircraft; however, there are many examples of close approaches by aircraft to sports venues (usually as part of the entertainment), so it would clearly be possible to mount such an attack.
The structural hazards would result from destruction of key load-bearing elements, though on the positive side the structural redundancy of these buildings is relatively high. Also, they typically contain few materials, such as carpets and furniture, that feed hot fires in enclosed buildings; on the other hand, their expanses of plastic seating would be a source of fuel. Fabric and hard-roof domes of sports stadiums may be tempting targets for a well-informed attack that destabilizes the self-equilibrating forces in the tendons and ring beams that support the roofs. In most instances, however, these supporting members would not be readily accessible to saboteurs (though they are vulnerable to aircraft impact).
Toxic chemicals and biohazards present similar threats to stadium crowds as to crowds in subways and other confined spaces: A lot of people are concentrated in a small area, making them vulnerable even to a highly localized attack. Terrorists willing to expose themselves to lethal doses could effectively spread chemical and biological toxins in these close quarters by hand. Dispersal patterns by HVAC would vary according to the types of agents involved, making the extent of their impact on the occupants difficult to predict. Biological, chemical, and radiological agents that could be employed are covered in Chapters 2, 3 and 4.
Panic also appears to be a significant hazard for crowds, sometimes even greater than that of the agent itself. Whether the cause is real or imagined, people reacting under panicked conditions could, for example, overwhelm exiting systems designed for normal (and relatively modest) flows, thereby causing many injuries and possible deaths. Panic and other intangible impacts on people are addressed in Chapter 9.
Schools and day-care centers deserve attention not because of the numbers of people typically present there but because harm done to them would so deeply affect the rest of us. Schools have evacuation plans for certain conditions and lockdown plans for others, which teachers and students regularly practice. But given that the typical buildings in which these activities are housed enjoy little or no hardening, not much could be done to defeat a direct attack of any significance—as was seen in the attack on Oklahoma City’s Murrah Building, which contained a day-care center. A greater likelihood of threat for schools and day-care centers comes from the secondary effects of an attack on some nearby