Document: NIST WTC Report Website

The collapse of New York City’s World Trade Center structures following the terrorist attacks of Sept. 11, 2001, was the worst building disaster in recorded history, killing some 2,800 people. More than 350 fire and emergency responders were among those killed, the largest loss of life for this group in a single incident.

In response to the WTC tragedy, the National Institute of Standards and Technology conducted a 3-year building and fire safety investigation to study the factors contributing to the probable cause (or causes) of post-impact collapse of the WTC Towers (WTC 1 and 2) and WTC 7; expanded its research in areas of high-priority need such as prevention of progressive collapse, fire resistance design and retrofit of structures, and fire resistive coatings for structural steel; and is reaching out to the building and fire safety communities to pave the way for timely, expedited considerations of recommendations stemming from the investigation.