ANSI - American National Standards Institute
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NIST Issues Final Report on Collapse of WTC Building 7

New York, Nov 24, 2008

The National Institute of Standards and Technology (NIST) has released its final report on the collapse of World Trade Center building 7 (WTC 7) in New York City on September 11, 2001. The report, based on a three-year investigation, identifies fire as the primary cause for the building’s collapse.

The scientific and technical building and fire safety investigation found that the fires on multiple floors in WTC 7 heated floor beams and girders, causing a critical support column to fail and prompting the progressive collapse that brought the building down. Based on these findings, the report contains thirteen recommendations, including increased structural integrity, enhanced fire endurance and active fire protection of structures, new methods for fire resistant design, improved emergency response, improved procedures and practices, and education and training.

A draft version of the report was first issued on August 21, 2008, for public comment and review. Although no significant changes were made to the report’s findings, the final version includes clarifications and supplemental text in response to comments by interested organizations and individuals worldwide.

The release of the final WTC 7 report marks the completion of NIST’s federal building and fire safety investigation of the WTC disaster, which began in August 2002.

A three-year study of the collapses of WTC towers 1 and 2 was completed in October of 2005. [see related article] As a result of these findings, more than twenty changes in the U.S. model building and fire codes have been adopted. Plans to implement additional changes to U.S. model building and fire codes based on the WTC 7 report are now underway.

The complete text of the final WTC 7 report, a video describing the WTC 7 investigation findings, all of all comments received on the draft WTC 7 report, and a chart tracking the progress toward implementing all of the NIST WTC recommendations can be found at

For more information, see the NIST news release.

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