The Fires in Building 7
Building 7 had a number of fires of limited extent and unknown duration before its precipitous total collapse at 5:20 PM. Official reports assume that debris from the fall of the North Tower ignited fires at 10:29 AM.
|This photograph from FEMA's report, and others like it, appear to be the only evidence of emergent flames.|
Photographs of the building's north face show only small, barely visible fires. Photographs of the building's east face, apparently from the mid-afternoon, show flames emerging from an isolated section of the 11th floor. Photographs of the building's west face, apparently from the late afternoon, show several areas with smoke stains, but don't show any flames. There appear to be no photographs of Building 7 from a time shortly before its collapse that show large active fires. The photograph below, taken in the afternoon, shows the upper half of Building 7 from the south. There are no signs of fire.
FEMA's report blamed the collapse of Building 7 primarily on fires, though it was inconclusive. NIST's investigation placed much more weight on claims of severe structural damage to the building. Nonetheless, all theories of the collapse that exclude demolition are necessarily primarily fire theories, since the building collapsed almost seven hours after incurring any structural damage from North Tower fallout. It is thus striking that other skyscraper fires exhibited fires that were far more extensive and long-lasting that Building 7's, but none of these other buildings collapsed.
Despite the fact that the fires in Building 7 were relatively small and short-lasting compared to other office fires, a decision was made not to fight them. Chapter 5 of FEMA's Report implies that lack of water was the basis for this decision:
This explanation is highly dubious given that Building 7 was only about two blocks from the Hudson.