Recommendation 8.21: Research is needed to determine how different toxins might be distributed, controlled, or filtered by buildings’ air handling and circulation systems. This work will lead to improved techniques for reducing the potential exposures of occupants. In the mean time, HEPA filters could be introduced where space and fan capacity are adequate to replace the simple dust filters currently in use, with the benefit of adding protection from anthrax and other bioterrorism materials.

Under the oversight of the OHS and NIST, this program could be performed by the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE), the relevant professional and standard-setting organization.

The exiting of tall buildings under emergency conditions deserves a special note. While the WTC twin towers collapsed with the loss of thousands of lives, the towers actually performed well in that occupants below the floors impacted by the airplanes were provided enough time, after the impacts and before the collapse, to exit the buildings safely. Occupants above the points of impact were not so fortunate because the impact and blast destroyed the stairwells for the multiple floors over which the impact occurred and egress from the upper floors was cut off. It would be appropriate to review emergency egress and related communications systems requirements for tall buildings in light of the WTC experience. Communication systems that provide information to both occupants and first responders about the location and status of egress routes is an essential element for survival.

Recommendation 8.22: The requirements for emergency egress and communications for tall buildings should be reexamined by the National Fire Protection Association in light of the WTC experience and the results of this reexamination should be used to determine appropriate modifications to building codes and standards.



Recent information indicates that popular venues such as ballparks, concert halls, and entertainment complexes (Disney World, for example) are at risk. In a broader context, mass rallies of any kind must also be considered potential targets, together with the gathering places of the nation’s intellectual, political, and financial elites and of its most vulnerable citizens—our children in their schools or day-care centers.

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