WTC Fire Temperatures and Egress

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WTCFire Temperatures and Egress

• Alana MacLellan-Bonnell
• Daniel Foley
• Michael Fitz

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Fire Temperature Analysis

• Variables
• Fuel
• Wind
• Ventilation
• Combustion efficiency
• Narrowed temperature by bounding it.

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Fire Temperature Analysis
Normal Flame Temperature
T (C)
300
500
700
900
From Kirks, Real-world Maximum Open Flame
temperatures of nearly all normal fuels burning
in turbulent Diffusion flames is about 900oC.
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Flashover

• Flashover all materials that can burn, are
  burning. Usually occurs at 20 kW/m2.
• 1200oF (650oC) - high end of Temperature
  associated with Flashover
• Ignition temp of CO (1128oF/609oC)
• Navy FFE (Turn Out Gear) designed for 45 sec. in
  flashover conditions

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Fire Temperature Analysis
Normal Flame Temperature
Flash Over

T (C)
300
500
700
900
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Transcripts

• 952 a.m.
• Battalion Seven Chief "Battalion Seven to
  Battalion Seven Alpha."
• "Freddie, come on over. Freddie, come on over by
  us."
• Battalion Seven Chief "Battalion Seven ...
  Ladder 15, we've got two isolated pockets of
  fire. We should be able to knock it down with two
  lines. Radio that, 78th floor numerous 10-45 Code
  Ones."
• Ladder 15 "What stair are you in, Orio?"
• Battalion Seven Aide "Seven Alpha to lobby
  command post."
• Ladder Fifteen "Fifteen to Battalion Seven."
• Battalion Seven Chief "... Ladder 15."
• Ladder 15 "Chief, what stair you in?"
• Battalion Seven Chief "South stairway Adam,
  South Tower."
• Ladder 15 "Floor 78?"
• Battalion Seven Chief "Ten-four, numerous
  civilians, we gonna need two engines up here."
• Ladder 15 "Alright ten-four, we're on our way."

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Fire Temperature Analysis
Less than Flashover
Normal Flame Temperature
Flash Over

T (C)
300
500
700
900
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Steel Damage

• Steel starts to glow at 550oC (Drysdale/Kirks)
• Dull red at 700oC (Drysdale/Kirks)
• Steel truss was at the highest point of each
  floor
• Steel subjected to the highest temperature on
  each floor.
• Steel seen glowing when fire subsided

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Room Conditions
Highest Temperatures
Fire Plume
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Fire Temperature Analysis
Less than Flashover
Normal Flame Temperature
Flash Over

T (C)
300
500
700
900
Glowing Steel
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Visual Comparison First Interstate and WTC
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Visual Comparison First Interstate and WTC
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Visual Comparison First Interstate and WTC
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Fire Temperature Analysis
Less than Flashover
Normal Flame Temperature
Flash Over
Room Temperature
Contact with Flame

T (C)
300
500
700
900
Glowing Steel
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Exiting/Egress Analysis
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Closer Look at Core Area
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Exiting/Egress Analysis

• The total floor plate area is
• 207.17 ft x 207.17 ft 42,918 ft2.
• The total area of the core is
• 87 ft x 137 ft 11,919 ft2.
• When determining the occupant load of a floor
  area, areas that are not normally occupied are
  excluded. The occupant area is therefore
• 42,918 ft2 11,919 ft2 30,999 ft2
• The occupant load factor (NFPA101) is
  100ft2/person, thus
• 30,999 ft2 / 100 ft2/person 309 persons per
  floor area

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Exiting/Egress Analysis
Door Capacity

• Generally doors to offices tend to be a standard
  size of 36 inches. Using this analogy, the doors
  to the stairs appear from the drawing to be
  similar in size. The exit capacity factor for a
  door was found to be 0.2 in/person (NFPA101).
  The exit capacity per door was determined to be
• 36 in / 0.2 in/person 180 persons per door
• There were 3 exit stair doors therefore
• exit capacity per floor of 540 persons

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Exiting/Egress Analysis
Stair Width

• Similar to the door, the exit capacity factor of
  the stairs was found to be 0.3 in/person. The
  total stair width required to serve the occupants
  per floor is
• 309 persons x 0.3 in/person 92.7 in
• The required width per stair is
• 92.7 in / 3 stairs 30.9 in required per stair
• The stair widths in the WTC were greater than 31
  inches.

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Exiting/Egress Analysis
Conclusion

• The calculations show that the exiting/egress
  system available in the WTC was adequate for the
  maximum expected occupants per floor.