Posted by  bob branson on September 25, 2001 at 18:07:12:

In Reply to:  Re: WTC Collapse posted by JohnMV. on September 24, 2001 at 01:01:46:

"The halon would have clearly killed 10's of 1000's
more."

HALON does not extinguish fires by depleting Oxygen, which is what CO2 will do, which you may be thinking of. Halon is an inert gas that disrupts the chemical reaction in the fire triangle - heat, fuel, oxygen. In proper discharge quanitites, even in a closed room, there are no health hazards at all. Also, I do not know of any building I have surveyed for insurance purposes that is protected with either a total flooding or local application HALON system. HALON is the best extinguishing agent so far but unfortunately is no longer being produced (except in very specialized applications) because it is an ozone depleting chemical.

You are probably correct about the heat and steam from sprinklers over a hot flammable liquid fire, but if close enough to the flames can cool the fire if discharged in heavy quantities. The WTC sprinklers were likely designed to control the relatively light fire load of an office occupancy fire and was not designed for extra hazard classes. I suspect that the initial impact from the jet impact took out enough of the sprinkler system piping to cause a tremendous loss of water pressure, essentially leave them with an ineffective fire sprinkler system, dripping water rather than discharging at a prescibed density. No conventionally designed sprinkler system would work in these circumstances.

Bob Branson

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