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The New York Times > New York Region > Report on Trade Center Collapses Emphasizes Damage to Fireproofing

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Report: National Institute of Standards and Technology

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Report on Trade Center Collapses Emphasizes Damage to Fireproofing


Published: April 5, 2005

he World Trade Center towers may have remained standing even after they were struck by aircraft if the impact had not dislodged fireproofing and if office furniture had not extended the life of the fires sparked by the jet fuel, a federal report released today concluded.

The report by the National Institute of Standards and Technology said its findings support the fact that the World Trade Center towers withstood the initial aircraft impact and "that they would have continued to remain standing indefinitely, but for another significant event such as the subsequent fires."

The agency was charged by Congress two years ago with investigating various aspects of the World Trade Center attacks on Sept. 11, 2001, including evacuation and rescue procedures, the quality of the buildings' steel, and how and why the buildings collapsed.

The group did not issue recommendations in its report today. It is scheduled to release the draft of its final report in June, followed by a final report with recommendations in September. The investigation has produced more than 10,000 pages of data, according to the agency.

The conclusions are in line with previous analyses that cited the intense heat of up to 800 degrees Fahrenheit as a central reason for the collapse - heat that would have been tempered if the fireproofing had not been stripped. But the report also said that while the architects of the towers had tested the impact of a Boeing 707 passenger jetliner crashing into the 80th floor of one of the buildings in 1964, they never envisioned the intense fires that engulfed the towers after the planes struck them.

The analysis released today concluded that there were about 8,900 people in the first World Trade Center tower and about 8,500 in the second tower. About 87 percent of the people were able to evacuate safely. The report found that of the approximately 2,567 victims, "20% or more ... may have been alive in the buildings just prior to their collapse."

Because only two of 198 elevators were working inside the towers after the jarring impact of the jet liners, those who had the best chance of safely evacuating from the floors not directly impacted were able to leave their offices relatively quickly, to find stairwells, and were in good enough physical shape to exit without resting between floors.

Still, the analysis determined that in the first tower, the average surviving occupant spent 48 seconds per floor descending the stairwell - 50 percent slower than the slowest speed predicted for non-emergency evacuations presented in a standard fire engineering text. Because of the slow pace of evacuation, the analysis said that had each of the towers been full -- or had about 25,000 employees in each -- the evacuation would have taken four hours and about 14,000 people would have died.

The report also found that the World Trade Center's high rise communication repeater was working properly, a finding that contradicts claims by some rescue workers.

The analysis found that while the impact of the planes destroyed and weakened the buildings' support columns, damaged water supply systems and dislodged fireproofing, the towers would have remained standing had it not been for the fires that weakened their support steel.

The report concluded that most of the fire damage was not caused directly by dispersed jet fuel from the aircraft, but by combustible office furniture inside the buildings.

"The jet fuel, which ignited the fires, was mostly consumed within the first few minutes after impact," the report stated. "The fires that burned for almost the entire time that the buildings remained standing were due mainly to burning building contents and, to a lesser extent, aircraft contents, not jet fuel."

The fires further weakened the support beams that caused floors to buckle and the buildings to list to the side. Without adequate fireproofing, the towers had little chance of surviving, the report found.

"The buildings would likely not have collapsed under the combined effects of aircraft impact and the subsequent jet fuel ignited multi-floor fires, if the fireproofing had not been dislodged or had been only minimally dislodged by aircraft impact," the report said.

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