Fire Protection System Requirements for
Applied to a building the size of one of the WTC towers (approx. 4000
sq.ft. per floor) the 'International Fire Codes' as outlined by the NFPA's
standard spec's "NFPA 13," require "automatic, quick response fire
detection sprinkler systems" in high-rise buildings to deliver a minimum
of 500 gallons of water per minute, for a minimum period of 2 hours.
That's 90,000 gallons of water! To compare, an olympic size swimming pool
contains a mere 64,800 gallons.)
This sprinkler system, or "Fail-Safe Deluge System" as it is called
technically, delivers this volume of water through a network of pipes
(steel at the time of the WTC's construction - newer, less demanding codes
allow plastic piping) to the walls, ceilings and windows of no less than
five floors - including the two floors above, and the two below the one in
which the fire was detected.
The water pressure in a fail-safe system is monitored, and when one or
more of the spray jets is triggered by higher than normal temperatures,
the "emergency power equipped" pumps sense the pressure drop and kick in.
This boosts the pressure in the system, which triggers the remaining spray
nozzles to open and commence to supply a "deluge" of water to the
Note: Any event which releases pressure from the system (i.e.: pipes that
have been ruptured, say by impact or explosion) would likewise cause the
system to activate - just as if it had been triggered by heat.
Total amount of water that's delivered per hour: 225,000 gallons - or nine
average size swimming pools.
The cooling capacity of this much water can be measured by calculating the
calories, or btu's it would take to raise the water temperature from room
temperature to 212 deg. F.
These figures, and more, will be be coming soon.