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Fire Suppression Systems. Federal Building and Fire Safety Investigation of the World Trade Center Disaster.

pdf icon Fire Suppression Systems. Federal Building and Fire Safety Investigation of the World Trade Center Disaster. (9210 K)
Hopkins, M.; Schoenrock, J.; Budnick, E.

NIST NCSTAR 1-4B; 278 p. September 2005.


World Trade Center; high rise buildings; building collapse; disasters; fire safety; fire investigations; terrorists; terrorism; fire hoses; hydraulic analyses; spray density; sprinkler systems; standpipes; fire suppression; water supply; codes; standards; sprinklers; evaluation; scenarios


The National Institute of Standards and Technology (NIST) conducted a building and fire safety investigation of the World Trade Center (WTC) disasters. The work documented in this report was performed in support of the investigation of active fire protection systems. Specifically, this effort involved documentation and evaluation of the automatic sprinkler and standpipe/pre-connected hose systems and their associated water supplies in WTC 1, 2, and 7. An extensive literature review was performed in order to document the installed fire suppression features. Hydraulic analyses were performed to provide estimates of the baseline capabilities of the suppression systems as well as capabilities under different fire incident scenarios, including the events of September 11, 2001. In general, the installed water supplies, automatic sprinkler, and standpipe/pre-connected hose systems in WTC 1, 2 and 7 met or exceeded the capabilities of systems typically installed to protect high-rise office buildings. The sprinkler systems were capable of providing adequate water densities to areas as much as two or three times the typical design areas. Based on initial building damage estimates, the sprinkler and standpipe systems sustained considerable damage in the impact areas of WTC 1 and WTC 2. However, even if the sprinkler systems had remained fully operational and had been designed to protect higher hazard levels (e.g., Extra Hazard), the size, number, and extended area of the initial fires would have opened a large number of sprinklers, involving floor areas significantly larger than those associated with the required water demand for the design area associated with the installed systems. For the most part, the water supplies provided redundant sources of water for the standpipe and sprinkler system infrastructures. However, the typical floor level sprinkler systems were installed with a single connection to a sprinkler riser, providing the potential for single points of failure. The standpipe/pre-connected hose systems were consistent with the applicable requirements of the Building Code of the City of New York, but were not consistent with the minimum flow rates and durations required in National Fire Protection Association (NFPA) 14. In addition, selected areas in all three buildings, including the generator fuel day-tank enclosures on several floors in WTC 7, were not protected by automatic sprinklers.