Summary of Findings
? The building was modern, in good condition, steel-framed with reinforced concrete floors, with high-specification class-A fire protection (2-3 hours’ fire-protection-rated and easily able to tolerate normal fires).
? Extensive damage was caused to the south face from falling debris, but the NIST report states that this was not a contributing factor in causing the building’s collapse. Engineers have demonstrated that if this damage were to be considered a major factor the building would have fallen asymmetrically, toppling in the direction of that damage.
? There is suspicion about what ignited the fires and when they started. NIST reports falling debris as a “likely” cause from the north tower collapsing at 10:28am, however, there were witness reports of “thick smoke” and an explosion from within Building 7 at about 9:30am which contradicts this claim.
? The fires were normal in size, the sort of fires to be expected in any normal office type environment. There was nothing extraordinary about their fuel source or location that might explain a prevention of effective fire-fighting operations.