The More You Know

The 1975 World Trade Center Fire

So, this was a very serious fire which spread over some 65 per cent of the eleventh floor (the core plus half the office area) in the very same building that supposedly "collapsed" on 9/11 due to a similar, or lesser, fire. This fire also spread to a number of other floors. And although it lasted over 3 hours, it caused no serious structural damage and trusses survived the fires without replacement and supported the building for many, many more years after the fires were put out.

It should be emphasized that the North Tower suffered no serious structural damage from this fire. In particular, no trusses needed to be replaced.

That the 1975 fire was more intense than the 9/11 fires is evident from the fact that it caused the 11th floor east side windows to break and flames could be seen pouring from these broken windows. This indicates a temperature greater than 700°C. In the 9/11 fires the windows were not broken by the heat (only by the aircraft impact) indicating a temperature below 700°C.

Physics and historical precedent is a real bitch.