The National Institute of Standards and Technology (NIST) releases nearly 500 pages of documents, detailing the latest findings of its investigation of the WTC collapses on 9/11. These include its hypotheses for the collapse sequences of each of the Twin Towers; details of their analysis of interviews with nearly 1,200 building occupants, emergency responders, and victims’ relatives; and information from their analysis of the emergency response and evacuation procedures. Their investigation into the collapses is based upon an analysis of thousands of photos and videos, examination of many of the elements used to construct the towers, and computer-enhanced modeling of the plane impacts and the spreading of the fires. Their hypothesis is that the towers collapsed ultimately due to the fires they suffered: As the fires burned, the buildings’ steel core columns buckled and shortened. This shifted more load to the buildings’ perimeter columns, which were already affected by the heat of the fires, and caused them to give way under the increased stress. Investigators have conducted a test with a reconstructed section of the WTC floor, and found that the original fireproofing was sufficient to meet the New York City building code. They say that had a typical office fire occurred in the towers, without the structural damage and the loss of some fireproofing caused by the plane impacts, it is likely the buildings would have remained standing. Lead investigator Dr. Shyam Sunder says, “The buildings performed as they should have in the airplane impact and extreme fires to which they were subjected. There is nothing there that stands out as abnormal.” NIST’s theories of why the WTC buildings collapsed conflict with an earlier investigation by FEMA, which claimed the collapse of the North Tower had begun in its core, rather than its perimeter columns (see May 1, 2002). [National Institute of Standards and Technology, 10/19/2004; New York Times, 10/20/2004]
March 20, 2006: Head of US Investigation on WTC Building 7 Does Not Know Why It Collapsed
Dr. S. Shyam Sunder, head of the National Institute of Standards and Technology government investigation into the collapse of the World Trade Center building, is asked about the collapse of WTC Building 7. Sunder says that he hopes to release something about that by the end of 2006. He adds, NIST did have some “preliminary hypotheses… We are studying the horizontal movement east to west, internal to the structure, on the fifth to seventh floors.… But truthfully, I don’t really know. We’ve had trouble getting a handle on building No. 7.” [New York Magazine, 3/20/2006]
August 21, 2008: Critics Unconvinced by NIST’s Claim that Explosives Not Used to Bring Down WTC 7
After the National Institute of Standards and Technology (NIST) announces the results of its investigation into the collapse of World Trade Center Building 7, some critics dispute its explanation for the collapse and question its apparent debunking of claims that explosives were used to demolish the building. The 47-story tower collapsed late in the afternoon of 9/11, even though no plane hit it (see (5:20 p.m.) September 11, 2001). Some have argued that fire and the falling debris from the Twin Towers’ collapses should not have brought down such a large steel and concrete structure. [Associated Press, 8/21/2008]
NIST Lacks ‘the Expertise on Explosives’ – James Quintiere, a professor of fire protection engineering at the University of Maryland who previously worked as the chief of NIST’s fire science and engineering division, says that NIST does not “have the expertise on explosives, so I don’t know how they came to that conclusion,” that explosives did not cause the collapse. However, Quintiere says he never personally believed explosives were involved. [Los Angeles Times, 8/22/2008] Richard Gage, a California architect and leader of a group called Architects and Engineers for 9/11 Truth, complains, “How much longer do we have to endure the cover-up of how Building 7 was destroyed?” The New York Times points out that “the collapse of 7 World Trade Center—home at the time to branch offices of the Central Intelligence Agency, the Secret Service, and the Giuliani administration’s emergency operations center—is cited in hundreds of Web sites and books as perhaps the most compelling evidence that an insider secretly planted explosives, intentionally destroying the tower.” [New York Times, 8/21/2008]
NIST Presentation – At a presentation of its findings earlier in the day, NIST announced that, in its three-year study of the collapse, it found no evidence showing explosives were used to bring the building down. [National Institute of Standards and Technology, 8/21/2008; National Institute of Standards and Technology, 8/21/2008] During his summary of the findings of NIST’s WTC 7 investigation (see August 21, 2008), lead investigator Shyam Sunder said, “We did not find any evidence that explosives were used to bring the building down.” [National Institute of Standards and Technology, 8/21/2008]
‘No Witness Reports’ of Loud Explosions – In the draft version of its final report on the collapse, which is released on this day (see August 21, 2008), NIST explains: “Blast from the smallest charge capable of failing a critical column… would have resulted in a sound level of 130 dB to 140 dB at a distance of at least half a mile if unobstructed by surrounding buildings.… This sound level is consistent with standing next to a jet plane engine and more than ten times louder than being in front of the speakers at a rock concert. There were no witness reports of such a loud noise, nor was such a noise heard on the audio tracks of video recordings of the WTC 7 collapse.” [National Institute of Standards and Technology, 8/2008, pp. 44-45 
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NIST Rules out Thermite – Skeptics have argued that an incendiary material called thermite was used to bring down WTC 7 (see August 4, 2008), and this would not necessarily have created such a loud explosive boom. [New York Times, 8/21/2008] But in a fact sheet published on this day, NIST responds: “To apply thermite to a large steel column, approximately 0.13 lb of thermite would be needed to heat and melt each pound of steel. For a steel column that weighs approximately 1,000 lbs. per foot, at least 100 lbs. of thermite would need to be placed around the column, ignited, and remain in contact with the vertical steel surface as the thermite reaction took place. This is for one column… presumably, more than one column would have been prepared with thermite, if this approach were to be used. It is unlikely that 100 lbs. of thermite, or more, could have been carried into WTC 7 and placed around columns without being detected, either prior to Sept. 11 or during that day.” [National Institute of Standards and Technology, 8/21/2008] Sunder says that investigators therefore decided not to use their computer model to evaluate whether a thermite-fueled fire might have brought down WTC 7. Pointing to the omission, one skeptic says, “It is very difficult to find what you are not looking for.” [New York Times, 8/21/2008] In a 2006 fact sheet, NIST in fact admitted it “did not test for the residue” of explosives or thermite in the remaining structural steel from the WTC collapses (see August 30, 2006). [National Institute of Standards and Technology, 8/30/2006] And, as the New York Times notes, “Adding to the suspicion is the fact that in the rush to clean up the site, almost all of the steel remains of the tower were disposed of, leaving investigators in later years with little forensic evidence” (see Shortly After September 11, 2001 and September 12-October 2001). [New York Times, 8/21/2008]
Extensive Preparations for Demolition – NIST’s new fact sheet also points out: “For [WTC 7] to have been prepared for intentional demolition, walls and/or column enclosures and fireproofing would have to be removed and replaced without being detected. Preparing a column includes steps such as cutting sections with torches, which produces noxious and odorous fumes. Intentional demolition usually requires applying explosive charges to most, if not all, interior columns, not just one or a limited set of columns in a building.” [National Institute of Standards and Technology, 8/21/2008]
August 21, 2008: NIST Rules out Diesel Tanks in Collapse of WTC 7
The National Institute of Standards and Technology (NIST) publicly rejects the theory that diesel fuel tanks installed in World Trade Center Building 7 played any role in the 47-story tower’s collapse, late in the afternoon of 9/11. This is clearly set out in a question-and-answer factsheet published on this day, together with an announcement of NIST’s draft report on the building’s collapse (see August 21, 2008 and August 21, 2008). The factsheet asks, “Did fuel oil systems in WTC 7 contribute to its collapse?” The answer is “No…. The worst-case scenarios associated with fires… could not have been sustained long enough, could not have generated sufficient heat to weaken critical interior columns, and/or would have produced large amounts of visible smoke from the lower floors, which were not observed.” [National Institute of Standards and Technology, 8/21/2008; New York Times, 8/21/2008] These findings are echoed in the draft version of its final report on the collapse. [National Institute of Standards and Technology, 8/2008, pp. xxxii ] WTC 7 had three emergency power systems, all of which ran on diesel fuel. The systems contained two 12,000 gallon fuel tanks and two 6,000 gallon tanks located beneath the building’s loading docks, and another 6,000 gallon tank on its first floor. There were also 275 gallon tanks on the fifth, seventh, and eighth floors, and a 50 gallon tank on the ninth floor. [National Institute of Standards and Technology, 8/21/2008] It has previously been suggested that diesel stored in these tanks might have contributed to fires that led to WTC 7’s collapse (see March 2, 2002). [New York Times, 3/2/2002] This possibility was proposed in the final report of the Federal Emergency Management Agency (FEMA) investigation of the WTC collapses, published in May 2002 (see May 1, 2002). [Federal Emergency Management Agency, 5/1/2002, pp. 5-28 – 5-29] But in his summary of the findings of NIST’s three-year study of WTC 7, lead investigator Shyam Sunder says the building’s collapse was “not due to fires from the substantial amount of diesel fuel stored in the building.” [National Institute of Standards and Technology, 8/21/2008]
August 21, 2008: NIST Announces Conclusions of WTC 7 Investigation, Presents New Theory for Collapse
The National Institute of Standards and Technology (NIST) announces the findings of its study of the collapse of World Trade Center Building 7, and says the 47-story tower fell late in the afternoon of 9/11 primarily due to fires. [National Institute of Standards and Technology, 8/21/2008; National Institute of Standards and Technology, 8/21/2008] NIST releases its findings as part of a 915-page report, which is the result of three years’ work by over 50 federal investigators and a dozen contractors (see August 21, 2008). [New York Times, 8/21/2008]
Collapse Is ‘No Longer a Mystery’ – In a news conference at NIST’s headquarters in Gaithersburg, Maryland, lead investigator Shyam Sunder admits: “[W]e knew from the beginning of our study that understanding what happened to Building 7 on 9/11 would be difficult. It did not fit any textbook description that you could readily point to and say, yes, that’s why the building failed.” But, he says, “[T]he reason for the collapse of World Trade Center 7 is no longer a mystery.” [National Institute of Standards and Technology, 8/21/2008; New York Times, 8/21/2008]
‘New Phenomenon’ Caused Collapse – Sunder says the “critical factor” that initiated the collapse was “thermal expansion of long-span floor systems located in the east side of the building,” and adds that NIST’s study “has identified thermal expansion as a new phenomenon that can cause structural collapse. For the first time we have shown that fire can induce a progressive collapse.”
Collapse Sequence – Sunder describes the sequence of events NIST believes led to the collapse of WTC 7. He says debris from the collapse of the north WTC tower “started fires on at least 10 floors of the building. The fires burned out of control on six of these 10 floors for about seven hours. The city water main had been cut by the collapse of the two WTC towers, so the sprinklers in Building 7 did not function for much of the bottom half of the building.” He continues: “Fires on floors 7 through 9 and 11 through 13 were particularly severe.… Eventually, a girder on floor 13 lost its connection to a critical interior column.” Floor 13 collapsed, beginning a cascade of floor failures down to the fifth floor. “With the support of these floors gone, column 79 buckled, which initiated the fire-induced progressive collapse of the building.… This in turn caused the failure of nearby columns 80 and 81 and floor failures up to the roof line.… As the roof line begins to fall adjacent columns buckle as well. In quick succession, the remaining interior columns failed from east to west across WTC 7, until the entire core began moving downward. Finally, the remaining outer shell or façade of the building fell.”
NIST Created ‘Virtual WTC 7’ Model – Sunder says that NIST reached its conclusions about the collapse “by reconstructing the entire building, beam by beam, column by column, connection by connection into a computer model, a virtual WTC 7 building. We then filled that virtual building with as much detail as possible about exactly what types of furnishings were on each floor. Then we set fire to those virtual offices on the floors where video and other visual evidence told us the fires burned.” The investigators “used a well-validated computer program developed at NIST, for studying the growth and spread of fires, to calculate temperatures throughout the building.… And we used well-established data on the properties of structural steel, the sprayed fire resistive material or fireproofing, and other building materials to determine how those temperatures affected the structure.”
Explosives Not Used – Sunder says that the investigators “did not find any evidence that explosives were used to bring the building down” (see August 21, 2008), nor was the collapse “due to fires from the substantial amount of diesel fuel stored in the building” (see August 21, 2008). NIST commenced its investigation of the WTC collapses in 2002 (see August 21, 2002) and issued its findings on the collapses of the Twin Towers in October 2005 (see October 26, 2005). Since then it has been focused on WTC 7. [Government Computer News, 8/21/2008; National Institute of Standards and Technology, 8/21/2008]
Final Report to Be Released – After suggestions are made by members of the public in response to its current report, NIST will release a finished version of the same report in November 2008, thereby completing its WTC investigation (see November 20, 2008). [National Institute of Standards and Technology, 11/20/2008]
