posted on Apr, 7 2005 @ 02:14 PM
Originally posted by Aelita
As to the fireproofing, I don't buy this argument wither. It has never been established what exactly the temperature was when the fuel was burning.
There is an argument that the black smoke was an indication that the flames were oxygen-starved (I believe that), therefore the temperature was
moderate and the steel didn't reach the critical point.
The argument that the fire did not reach high temperatures because it was oxygen limited is false. I think that this misunderstanding originated when
some people misapplied the behavior of welding gasses to a structural fire situation.
The amount of heat measured in joules, released by a given reaction is fixed. If one of those reactants is limited, then the total number of joules
release will be limited by that factor.
The thing to remember here is that the amount of fuel on the floor was HUGE. You are talking about thousands of gallons of jet fuel, thousands of
pounds of paper, plastics, wood, etc. The fire was less oxygen starved as it was fuel rich. I know that sounds like a petty distinction, but
consider the huge holes in the side of the building and the breached shaft walls in the core. There was plenty of oxygen to release a tremendous
amount of heat. There wasn’t enough to burn ALL of the fuel efficiently, but there was enough heat being released to cause the fire to spread many
floors up the building in a short span of time.
One of the problems is that when comparing this type of situation with say a welding torch, or even when considering the adiabatic flame temperature
of the fuel, people tend to forget that those situations are based on the conditions that the fuel temperature (i.e. welding gas, or the ideal
adiabatic flame value) is at 20 C.
In a structural fire, The fuel heats up also.
As the temperature of the material increases, the oxygen level required for ignition decreases. And the temperature produced by it combustion
Finally If the fire was oxygen limited, then it would have produced large amounts of partially pyrolized gasses as well as hot carbon monoxide. These
are flammable and can explode reach a condition known as flashover. This is very common in structure fires and will result in a huge heat release.