World Trade Centre

The World Trade Centre was a complex of seven office buildings on the west side of lower Manhattan. The first two buildings, known only World Trade One and World Trade Two were identical, and were, at the time, the tallest buildings in Manhattan,

Construction of the twin towers began on August 5, 1966. The twin towers opened on 1973, and they were destroyed as part of a terrorist attack, on September 11, 2001. Terrorists crashed a large airliner into each building, causing almost 3,000 deaths. Fires from the jet fuel heated steel beams so hot they lost their structural integrity. The second tower to be hit collapsed under one hour after it was hit. The first twower to be hit lasted one hour and forty-two minutes. World Trade Seven was the third tallest building in the complex. It too was swept by fire, from debris. That fire couldn't be controlled after the collapse of the first two towers broke all nearby fire mains.

Terrorists had attacked the towers, earlier, in 1993. That attack was through a truck, loaded with explosives, parked in an underground parking garage. That attack kiiled 6 people. It also triggered a fire, that wasn't immediately controlled, that required complete evacation of the building.

The death toll from the 2001 attack would have been much greater if the first attack hadn't occurred before 9am, when many office workers hadn't arrived. It is estimated the towers only held about 15,000 people, 30 percent of its normal daytime population.

The building was full, in 1993, and the long evacuation exposed a serious weakness in the design of the safety systems. It was only eqipped with three stairwell -- which the 1993 attack proved was inadequate. It took over four hours to evacuate, with just three stairwells. Further emergency stairwells are not designed to have their doors jammed open. Powerful fans are in place to suck smoke from the stairwells. But those fans can't work if evacuees keep those doors open, as they wait their turn. All the evacuees emerged with black soot they had inhaled, and subsequently breathed out, surrounding their noses and throats.

And yet no steps were taken to convert some of the building's office space to new emergency stairwells.