What are the observational characteristics of the fires?
Both towers smoke clouds became dark, indicating an oxygen starved fire. Oxygen starved fires are cooler than equivalent fires with an effective air flow. The twin towers differed in the fire movement. WTC 2’s fires rapidly reached the east side of the building in 10-20 minutes, whereas the fires in WTC 1 took about 50-60 min’s to reach the north side[6].
