As an aside the temperature issue is also quite interesting NIST shows some figures of simulations in which the fire first heats up to  C in parts of the northern side then the fire moves to the south heats up there while the northern side is cooling down The northern side did not collapse but the southern side did with minimal differences in simulated temperatures At the same time the buildings are supposed to have collapsed symmetrically due to a fire which was according to NISTs own report very asymmetric at the time of collapse NIST also apparently overestimated the oxygen consumption of the fire by assuming that available oxygen would be burnt instantly ie gaseous products of the fire would have to move away instantly etc It was a rather calm ie not windy day however and there is no evidence of any chimney effect ie much of the smoke is exiting the tower through the broken windows which are also the entry point for the oxygen