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Occupant Behavior, Egress, and Emergency Communication. Federal Building and Fire Safety Investigation of the World Trade Center Disaster (NIST NCSTAR 1-7) ***DRAFT for Public Comments***



Jason D. Averill, Dennis S. Mileti, Richard D. Peacock, Erica D. Kuligowski, N Groner, Guylene Proulx, Paul A. Reneke, Harold E. Nelson


Multiple sources of information were collected and analyzed: over 1,000 new interviews with survivors (including 803 telephone interviews, 225 face-to-face interviews, and 5 focus groups); over 700 published interviews; 9-1-1 emergency calls; transcripts of emergency communications, historical building design drawings, memoranda, and calculations; formal complaints filed with the Occupational Safety and Health Administration; and other relevant materials. The egress system, including stairwells and elevators, was described and compared to requirement of both contemporary and current code requirements. This report documents the emergency procedures, both as they were designed to be implemented, as well as how they were actually implemented on September 11, 2001. The population in WTC 1 and WTC 2 on September 11, 2001, at 8:46:30 a.m. was enumerated and described, where the characteristics of the population were relevant to the subsequent evacuation, including training, experience, mobility status, among others. The progress of the evacuation of both towers was described in a quasi-chronological manner from 8:46:30 a.m. when WTC 1 was attacked, until 10:28:22 a.m., when WTC 1 collapsed. Causal models were built to explore the sources of evacuation initiation delay (why people did not immediately start to leave the building) as well as normalized stairwell evacuation time (how long the average occupant spent in the stairwells per floor). Issues identified as contributing to either speeding or aiding the evacuation process were explored. Egress simulations provided context for estimating how long WTC 1 and WTC 2 would have taken to evacuate with different populations, using different models, and subject to different damage to the building.
National Construction Safety Team Act Reports (NIST NCSTAR) - 1-7
Report Number


World Trade Center, high rise buildings, building collapse, disasters, fire safety, fire investigations, terrorists, terrorism, building fires, egress, communication networks, evacuation, human behavior


Averill, J. , Mileti, D. , Peacock, R. , Kuligowski, E. , Groner, N. , Proulx, G. , Reneke, P. and Nelson, H. (2005), Occupant Behavior, Egress, and Emergency Communication. Federal Building and Fire Safety Investigation of the World Trade Center Disaster (NIST NCSTAR 1-7) ***DRAFT for Public Comments***, National Construction Safety Team Act Reports (NIST NCSTAR), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed June 20, 2024)


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Created September 1, 2005, Updated February 19, 2017