10:28 a.m.-5:20 p.m. September 11, 2001: WTC 7 Suffers Fires ‘on at Least 10 Floors’

World Trade Center Building 7 (WTC 7) suffers fires on several floors, some of which last until 5:20 p.m., when the building collapses. [National Institute of Standards and Technology, 8/21/2008] WTC 7 is a 47-story office building located just north of the Twin Towers. It is damaged when the north WTC tower (WTC 1) collapses at 10:28 a.m. (see 10:28 a.m. September 11, 2001). [National Institute of Standards and Technology, 11/2008, pp. 2, 16]
Fires Started by Collapse Debris – Two official reports on the collapse of WTC 7 will tentatively conclude that fires in this building are initiated by debris that is ejected when the North Tower collapses (see 10:28 a.m. September 11, 2001). In a 2002 report (see May 1, 2002), the Federal Emergency Management Agency (FEMA) will state, “It is likely that fires” in WTC 7 “started as a result of debris from the collapse of WTC 1.” [Federal Emergency Management Agency, 5/1/2002, pp. 5-20] In a 2008 report (see November 20, 2008), the National Institute of Standards and Technology (NIST) will state, “Most likely, the WTC 7 fires began as a result of burning debris from the collapse of WTC 1.” However, NIST will add, “visual evidence of fires in the building was not available until around noon.” [National Institute of Standards and Technology, 11/2008, pp. 18]
Fires Spread in WTC 7 – According to NIST, fires are ignited “on at least 10 floors” of WTC 7, but “only the fires on floors 7 through 9 and 11 through 13 grew and lasted until the time of the building collapse.” [National Institute of Standards and Technology, 11/2008, pp. xxxvi] NIST will state, “Early fires were seen on the southwest corner of floors 19, 22, 29, and 30 shortly after noon,” but “These were short-lived.” [National Institute of Standards and Technology, 11/2008, pp. 51] The fires on floors 7 to 9 and 11 to 13, however, “grew and spread, since they were not extinguished either by the automatic sprinkler system or by [the New York City Fire Department], because water was not available in WTC 7.” Fires are “generally concentrated on the east and north sides of the northeast region beginning at about 3 p.m. to 4 p.m.” [National Institute of Standards and Technology, 11/2008, pp. 21] The fires on floors 7 to 9 and 11 to 13 have “characteristics similar to those that have occurred previously in tall buildings,” according to NIST, and “Their growth and spread [are] consistent with ordinary building contents fires.” [National Institute of Standards and Technology, 11/2008, pp. xxxvi] These fires are “fed by combustibles (e.g., desks, chairs, papers, carpet) that were ordinary for commercial occupancies.” However, NIST will point out, there is “no evidence that the fires spread from floor to floor, except, perhaps, just prior to the collapse of the building.” [National Institute of Standards and Technology, 11/2008, pp. 51-52]
Limited Evidence Available – Both FEMA and NIST will admit that their accounts of the fires in WTC 7 are based upon imperfect evidence. In its report on the WTC collapses, published in May 2002, FEMA will note, “Currently, there is limited information about the ignition and development of fires at WTC 7.” [Federal Emergency Management Agency, 5/1/2002, pp. 5-20] In the final report of its investigation of the collapse of WTC 7, NIST will point out that “available images showing fires in WTC 7 did not allow the detailed description of fire spread that was possible for the WTC towers.” The report will add: “It must be kept in mind that [NIST’s] fire observations were based on images of the exterior faces, which provided little indication about the behavior of fires well removed from the exterior walls. It is likely that much of the burning took place beyond the views of the windows.” But, the report will state, “[T]here was sufficient information to derive general descriptions of fire ignition and spread on various floors of the building.” [National Institute of Standards and Technology, 11/2008, pp. 18]
NIST Blames Fires for Collapse – WTC 7 collapses at 5:20 p.m. this afternoon (see (5:20 p.m.) September 11, 2001). In late 2008, at the end of its investigation into WTC 7’s collapse, NIST will blame the fires WTC 7 suffers for causing its collapse (see August 21, 2008 and August 21, 2008). NIST will state: “The heat from the uncontrolled fires caused steel floor beams and girders to thermally expand, leading to a chain of events that caused a key structural column to fail. The failure of this structural column then initiated a fire-induced progressive collapse of the entire building.” [National Institute of Standards and Technology, 8/21/2008; National Institute of Standards and Technology, 11/2008, pp. xxxvi-xxxvii] However, critics will dispute this conclusion, instead blaming explosives for the collapse (see August 21, 2008). [New York Times, 8/21/2008] FEMA will offer no firm conclusions about the possible role fires play in causing WTC 7 to collapse. In its 2002 report it will state, “The specifics of the fires in WTC 7 and how they caused the building to collapse remain unknown at this time.” [Federal Emergency Management Agency, 5/1/2002, pp. 5-31]