Jason D. Averill

Fire Protection Engineer

Building and Fire Research Lab

National Institute of Standards and T

U.S. Department of Comme

Technical Conference on the Federal 

Fire Safety Investigation of the World T

(WTC) Disaster

September 13 – 15, 2005

Occupant Behavior, Egress, and Em

Communications
Singnificant Singnificant Contributors Contributors

NIST

Jason AverillRichard PeacockErica KuligowskiPaul RenekeElisa BakerJohnathan Demarest

Expert Contractors

Norman GronerDennis MiletiHarold NelsonGuylene Proulx

NuStats Partners

Johanna ZmudRob SantosHeather ContrinDella SantosCarlos Arce

NuStats Subcont

Jamie AbelsonNancy McGuckJon KrosnickMartha Van HaiVirginia Bartot
Purpose and Outcomes Purpose and Outcomes

Purpose: To determine the behavior and fa

occupants and responders by collecting information on:

•

occupant behavior

•

human factors

•

egress

•

emergency communications

•

evacuation system

Desired Outcomes

•

Enhanced evacuation systems

•

Enhanced safety of occupants
Overview Overview

• Data Collection• Egress System• Chronology of Evacuation• Causal Modeling• Egress Modeling• Principal Findings
Collection of First Person Account

Collection of First Person Accoun

225 Face-to-face Intervie

803 Telephone 6 

Interviews 
Other Activities Other Activities

• Other Data Collection

• 9-1-1 Records• Published Accounts• Written Communications, Protocols, and • Scientific Literature

• Causal Modeling• Egress Modeling• Observations Fire, Smoke, and Damage
WTC Site Plan WTC Site Plan 

– Plaza Level Plaza Level
WTC Site Plane WTC Site Plane – Concourse Leve

Concourse Leve
WTC 1 Building Plan WTC 1 Building Plan 

– Concourse 

Concourse 
WTC 2 Building Plan WTC 2 Building Plan 

– Concourse 

Concourse 
Stairwells Stairwells

3 Stairwells

(2) 44 in. Stairwells(1) 56 in. Stairwell

Transfer Hallways 
Elevators Elevators

106 Elevators in Each TowerInnovative SkylobbyConfiguration
September 11, 200

Moments Before 8:46 a
Building Population Building Population

WTC1 WTC2 

Estimated Total Population of Survivors* 7,500** 7,900 

Statistical Precision Calculations

Sample n

427 376

Stand

ard Error (p) 1.90

% 1.92

% 

Stand

ard Error (Total)

750 900 

Number of Decedents

Decedents 1,434*** 599*** 

Total Building Population

Total 8,900 8,500 

* Includes only occupants with badges

** includes only occupants below floor 92. 

*** Calculated from Cauchon as 1,434 + 599

**** Calculated as 2,749 – 403 first responders – 157 airplane 
Occupant Characteristics Occupant Characteristics

1975

1976

1977

1978

1979

1980

0.0%5.0%

10.0%15.0%

20.0%25.0%

Percent

Years 

Valid 439

Refuse 1

Mean 45

Median 46

Minimum 22

Maximum 73

N

Age

WTC 1

Maximum 74

Minimum 21

Median 44

Mean 45

Refuse

2

N Valid 361

1975

1976

1978

1979

1980

1981

0.0%5.0%

10.0%15.0%

20.0%25.0%

PercenWTC 2 t
World Trade Center Occupant Prep

World Trade Center Occupant Pre

•

During the year from Sep. 11, 2000 to Sep. 

many fire drills did you take part in at the WoCenter? 

• At least one: 66%• None: 17%;• Don’t know: 17%

• 93% of fire drill participants were shown clos•

Approximately half (51%) of WTC occupants 

used a stairwell at the World Trade Center pSeptember 11th.
September 11, 200

8:46 a.m.
WTC 1 Impact WTC 1 Impact

Before Immediate
WTC 1

WTC 1 -

Fi

Felt something (bmoving, impact, sswaying)Heard something crash, explosion, Saw airplane Other 

“I saw the plane halfway in the 

building.” (Floor in the 90’s)

“The door blew open from the closet, 

causing my chair to hit the desk.” (Floor in the 50’s) 

“We felt the entire building shake and 

saw some people who were sitting in chairs slide across the floor.” (Floor 10’s)

“I was walking through the mall 

towards tower one to get to the elevator. The lights flickered. I stopped in my tracks and looked around....At this point, the revolving doors exploded. They seemed to vaporize.” (Concourse)

Data consistent tOnly small numbe

and smoke at 
Observations of Building Damage, 

Observations of Building Damage

Observations from i

ntervi

ews, e

mergency calls, or published accounts.

‘?’ indicates a floor where no observer was found after i

mpact, a blank i

ndicates 

that an observer did not report that conditi

on. Additional analysis pendi

ng.

MER

Smoke

Sprinklers / water

Fatally injured people

Power outage

Jet fuel

Fallen ceiling tiles

Fire alarms

Collapsed walls

Extreme heat

Fire

Fireballs

–– 110

????? ???? ? ?

*

????? ???? ? ?

–– 100

????? ???? ? ?????? ???? ? ?????? ???? ? ?

**

–– 90–– 80

Smoke

Sprinklers / water

Fatally injured people

Power outage

Jet fuel

Fallen ceiling tiles

Fire alarms

Collapsed walls

Extreme heat

Fire

Fireballs

–– 70–– 60–– 50

Smoke

Sprink

????????????

Smoke

Sprinklers / water

Fatally injured people

Power outage

Jet fuel

Fallen ceiling tiles

Fire alarms

Collapsed walls

Extreme heat

Fire

Fireballs

–– 110

????? ???? ? ?

*

????? ???? ? ?

–– 100

????? ???? ? ?????? ???? ? ?????? ???? ? ?

**

–– 90–– 80

Smoke

Sprinklers / water

Fatally injured people

Power outage

Jet fuel

Fallen ceiling tiles

Fire alarms

Collapsed walls

Extreme heat

Fire

Fireballs

–– 70–– 60–– 50

Smoke

Sprink

????????????
WTC 2

WTC 2 – First Awareness

Felt or heard a boom, explosion, or rumble*

61%

Saw smoke, flames, airplane, or debris*

19%

Warned by someone else 12%By phone, public address announcement, television or radio 

2%

Other means 6%

“I saw the plan

(Floor in th

“I noticed it wa

saw massiflames wraaround the the 90’s)

“My boss cam

evacuate.” 

“I heard a loud 

in the 10’s)

*Primarily from Tower 1

Observations vary by floor (height).Many observations of fire(ball), 

debris
September 11, 200

8:47 a.m. –

9:02 a.m
WTC 1

Time to E

0 20 

Percent Beginning Evacuation

05

1015202530

WTC 2 Hit

• 92% of surv

evacuation was hit; 29% 

• 21% exited 

WTC 2 was 

“In the hallway...there were no 

walls left...and the bathroom seemed to be missing. There was a hole in the wall near the elevator (in the hall) and fire was coming up onto our floor through that hole. (Floor in the 90’s)

“To me everything seemed 

normal, all the ceilings were fine, the electricity was fine...” (Floor in the 70’s)

“I was close to the windows. The 

windows were broken and I saw things from the office were going out the window.” (Floor in the 20’s)
WTC 2

“We were instr

uc

offices and thsecure. So, I office. As I eand met my sthat he wantebuilding and instruction to 90’s)

“Heard the build

announcemethe stairs to eto a uniformedoor open in lobby. We wstairwell area elevators to gkept on goin(Floor in the 

Time to Evacuation Start (min)

0 20 40 60 0

Percent Beginning Evacuation

05

1015202530

WTC 2 Hit

WTC 2 Collapse 8

• 91% began evacuating before Tower 2 was hit; 22% within one minute.• 41% of the survivors exited the building before WTC 2 was hit.
WTC 1

Life in Danger? Others

Self

Initial Awareness 48% 41%Interim Period 63% 52% Activities B

Talked to others Gathered persoHelped others Searched for otTalked on telepMoved between Fought fire or smShut down comContinued workOther activities 

“As I was leaving, it didn't seem as 

bad as I thought in the office and I decided that I would just walk all the way down and reassess the situation and go back to the office if things were OK.” (Floor in the 70’s)

“I felt that my life was threatened. I 

also thought of 1993 bombing and I know what some of my friends went through.” (Floor in the 70’s)

“I felt safe because I watched 

previous documentaries and I was informed that I was safe in my building. I went back to the fax machine.” (Floor in the 60’s)
WTC 2

Used elevator for entire evacuation

• “The decision to use the 

elevators was based on the fact that there was no fire in our building.” (Floor in the 100’s)

Used stairs and elevators

• “I was raised in Los Angeles; I 

was taught that in case of emergency situations and disasters to avoid elevators” (Floor in the 100’s) – Decision was made to use stairs until the PA announcement, when respondent used an elevator to evacuate.

Initial Eva

Stairwell A Stairwell B Stairwell C Stairwell A or C Used elevator Don’t Know [Sta

Did not consider el

•“I knew one selevator in an situation” (Floo
September 11, 200

9:03 a.m.
WTC 2 Impact WTC 2 Impact

Stairwell A was passable for a period of time after WTC 2 was attacked. NIST identified 18 individuals who used this path, although one died from 9/11 related injuries. At least two people from below the impact region went up to help and did not successfully evacuate.
WTC 2

•“It was clear that something hit the building...the stairwell swayed and it was as if the building was doing the ‘twist’.” (Floor in the 90’s)•“I felt an explosion and saw fire and smoke coming from the corridor. The whole building was shaking and breaking glass was cascading down the building. The smoke was a light grayish and the flames leapt out of the corridor from the pressure.” (Floor in the 70’s)•“I heard a loud nois

e, felt the 

building shake, and the temperature in the air went up.” (Floor in the 60’s)

Observa

Still 

Power outFallen CeiJet Fuel Smoke Collapsed Fire or flaFire alarm Fatally injpeople Extreme hSprinklers 
Observations of Building Damage, 

Observations of Building Damage

MER

Observations from i

ntervi

ews, e

mergency calls, or published accounts.

‘?’ indicates a floor where no observer was found after i

mpact, a blank i

ndicates 

that an observer did not report that conditi

on. Additional analysis pendi

ng.

Smoke

Sprinklers / water

Fatally injured people

Power outage

Jet fuel

Fallen ceiling tiles

Fire alarms

Collapsed walls

Extreme heat

Fire

Fireballs

? ??? ??? ??? ? –– 110? ??? ??? ??? ?? ??? ??? ??? ?? ??? ??? ??? ?? ??? ??? ??? ?

–– 100

? ??? ??? ??? ?? ??? ??? ??? ?? ??? ??? ??? ?? ??? ??? ??? ?

* *

? ??? ??? ??? ?? ??? ??? ??? ?? ??? ??? ??? ? –– 90? ??? ??? ??? ?? ??? ??? ??? ?? ??? ??? ??? ?

–– 80

? ??? ??? ??? ?

Smoke

Sprinklers / water

Fatally injured people

Power outage

Jet fuel

Fallen ceiling tiles

Fire alarms

Collapsed walls

Extreme heat

Fire

Fireballs

–– 70

? ???? ??? ???

–– 60

? ???? ??? ???? ???? ??? ???? ???? ??? ???? ???? ??? ???? ???? ??? ??? –– 50? ???? ??? ???? ???? ??? ???? ???? ??? ???? ???? ??? ???? ???? ??? ???

Smoke

Sprinkle

? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??

Smoke

Sprinklers / water

Fatally injured people

Power outage

Jet fuel

Fallen ceiling tiles

Fire alarms

Collapsed walls

Extreme heat

Fire

Fireballs

? ??? ??? ??? ? –– 110? ??? ??? ??? ?? ??? ??? ??? ?? ??? ??? ??? ?? ??? ??? ??? ?

–– 100

? ??? ??? ??? ?? ??? ??? ??? ?? ??? ??? ??? ?? ??? ??? ??? ?

* *

? ??? ??? ??? ?? ??? ??? ??? ?? ??? ??? ??? ? –– 90? ??? ??? ??? ?? ??? ??? ??? ?? ??? ??? ??? ?

–– 80

? ??? ??? ??? ?

Smoke

Sprinklers / water

Fatally injured people

Power outage

Jet fuel

Fallen ceiling tiles

Fire alarms

Collapsed walls

Extreme heat

Fire

Fireballs

–– 70

? ???? ??? ???

–– 60

? ???? ??? ???? ???? ??? ???? ???? ??? ???? ???? ??? ???? ???? ??? ??? –– 50? ???? ??? ???? ???? ??? ???? ???? ??? ???? ???? ??? ???? ???? ??? ???

Smoke

Sprinkle

? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??
WTC 1

“I felt the air clear 

gush of wind tsmoke (this habuilding 2 was (Floor in the 6

“The building sho

the first time [stopped briefl

(Floor in the 6

“Very soon after e

someone with communicatioword that a cothe building. clarified as to Later [there wsecond plane 50’s)

Some noticed minor 

disturbances when WTC 2 was hit; many never mentioned anything related to Tower 2 being hit.

“I answered the [cellular] phone and my wife was telling me that another plane had struck Tower 2 and she said, ‘Get out of the building as fast as you can; it is a terrorist att

ack.’” (Floor in the 

40’s)
September 11, 200

After 9:03 a.m.
Reported Aids & Constraints to E

Reported Aids & Constraints to E

WTC 1

Evacuation 

Aids WTC 2

66%

Support from 

others 60%

44% Firefighters/Police 30%32% Exit signs 35%18%

Photoluminescent 

paint 11%

10% Floor Warden 13%

WTC 1

Evac

Cons

73%

Cro

sta

51% Firefigh24%

Lack 

instr

16% Locke11% Poor 

5%

Bad/

sig
Time Until Out of Buildin

Time Until Out of Buildin

0

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 

0

2

4

6

8

10

12

14

16

18

20

Percentage

Time Since WTC 1 Attack (mi

n)
September 11, 2001 September 11, 2001 WTC Evacua

WTC Evacua

0

102030405060708090

100

0 10 20 30 40 50 60 70 8

Time Since 

W

T

C 1 Attack (min)

Cumulative Percentage (%)

W

TC 2 Hit

W

TC 

WTC 2

WTC 1
Likely Location at Time o

World Trade Center 1 Occu

At or 

World Trade Center 2 Occu

At or 

Confirmed Below Impact in WTC 2Unknown Location Inside WWTC 2First Responders (Total) 

Hosp

Volunte

Bystander/Nearby Building American Flight 11 United Flight 175 No Information Total 

Decedent Analysis Decedent Analysis

September11Victims.com: This site is dedicated to 

the victims of September 11, 2001 tragedy.

Portraits: 9/11/01: Published by the New York Times 

in 2003, this book includes short interviews with family members of many decedents.

CNN.com In-Depth Special 

(http://www.cnn.com/SPECIALS/2001/memorial/index.html): Tribute site for people to write remembrances of decedents.

Badge List maintained by Port Authority of New York 

and New Jersey: Includes name, employer, building, and floor for all occupants with badgeaccess to WTC 1 or WTC 2.

Numerous memorial sites maintained by companies 

which lost employees: Includes names and remembrances of decedents. Examples include the Port Authority, Fire and Police Departments, Marsh & McLennan Companies, EuroBrokers, Fiduciary Trust, and others.

Newsday.com: Includes short stories written about 

specific decedents.

NIST Interviews with occupants and family members* Where possible, eyewitness accounts were used to place individuals.

Where no specific accounts existed, employer and floor information was used to place individuals.
Causal Modeling: WTC 1 Causal Modeling: WTC 1

The main process that led to evacuation delay: Environmental cues and initial floor led people to seek additional information and take actions which delayed the start of evacuation.
Causal Modeling: WTC 2 Causal Modeling: WTC 2

The main process that led to evacuation delay:Environmental cues and initial floor led people to perceive risk and these three 

factors led people to seek additional information and take actions which delayed the start of evacuation.
Causal Modeling: Causal Modeling:

Normalized Stairwell Evacuation T

Normalized Stairwell Evacuation T

Floor increased the odds of encountering environmental cues, which had a large and direct effect upon increasing the time people spent in the stairs. Additionally, interrupting evacuation increased stairwell residence time.
Egress Modeling: Minimum Time Egress Modeling: Minimum Time

Preliminary results from 

buildingEXODUS

Full Tower evacuation with the 

following assumptions:

• All able-bodied 

occupants

• Response delay = 0 sec.• No damage simulated• No elevator use• Continual stair 

movement (no resting in stairway)

Minimum M

o

v

em

0

20406080

100120140160

0 5000 10000 1500

Number of occupa

Evacuation Time (min)

8,800 - 9/11 capacity
Egress Modeling: Calibrated Mode

Egress Modeling: Calibrated Mode

Simulated evacuation results for full

WTC

1 and WTC

2 on September 

Percen

Successf

W

Buildi

n

g

Total 

Number of 

Occupants 

at t = 0.0

Potential 

Number 

of 

Evacuees

Occupants 

Remaining 

in Building

at Collapse

Occupants 

Trapped 

Above 

Floors of 

Impact

Total

WTC

1 19,800 16,000 6,200 3,800 69 % 

WTC

2 19,800 17,260 8,377 3,900 58 % 

Total 39,600 33,260 14,577 7,700 63 %
Occupant Preparedness Occupant Preparedness

• Occupants were often unprepared for the p

challenge of full building evacuation. Numrequired one or more periods of rest during descent or turned to elevators after finding strenuous.

• Occupants were often unprepared to encou

hallways during the stairwell descent. Grouoccasionally hesitated or debated a course encountering a transfer hallway.
Mobility Impaired Occupants Mobility Impaired Occupants

• Approximately 1,000 surviving occupants (a projec

percent reported in the telephone interviews) of Whad a limitation that impacted their ability to evacurecent surgery or injury, obesity, heart condition, aotherwise requiring assistance to walk, pregnancy

• Mobility Impaired occupants were not universally a• As the emergency responders started evacuating 

collapse of WTC 2, they found mobility impaired ostaircases going down.
Mobility Impaired Occupants, cont

Mobility Impaired Occupants, cont

• FDNY and PAPD personnel found 40 to 60 mob

occupants on the 12th floor of WTC 1 as they we

attempted to clear each floor on their way out. Tindividuals had been placed on a floor somewheand 20 in WTC 1 in an attempt to clear the stairw

• Emergency responders were assisting approxim

mobility impaired people down the staircase just collapse of WTC 1. It is unknown how many fatawith this group. 

• No mobility impaired rest station was reported in 
Emergency Communications Emergency Communications

•

Occupants called 9-1-1 and Port Authority se

and advice. 

•

Opportunities to improve occupants situat

were often lost. Specific knowledge abouand impact damage was only occasionallto occupants who requested the informatiwithout apparent coordination.

•

Some operators advised sheltering (e.g., 

while others advised evacuation (e.g., maDesk); some permitted window breaking winstructed occupants not to break window

•

The “right” advice with respect to a particu

howev

er, is highly sensitive to the caller’s 

and may be clear only in hindsight. 
Public Address System Announce

Public Address System Announce

WTC 1

Many announcement attempts were made 

Command Station in the lobby, initially to and then, within approximately ten minutebuilding. However, only two face-to-face WTC 1 reported hearing any announcemsource is unclear.

Conclusion:

Damage to the 22nd floor communicati

disabled building-wide announcement 
Public Address System Announce

Public Address System Announce

WTC 2, Prior to 9:03 a.m.~ 9:00 a.m. - There is a fire condition in WT

is secure. Please return to your offices. 

9:02 a.m. – “May I have your attention ple

situation is in Building 1. However, if conyour floor warrant, you may wish to start evacuation.”
Public Address System Announce

Public Address System Announce

WTC 2, After 9:03 a.m.

9:12 a.m. –

(Fire Command Station in WT

Radio Channel 22) “310-B to any units: Be aBuilding Two (inaudible) only (inaudible) waWe can't pick up warden phones. We are justraight announcements telling the people nthe warden phones, because we can't pick t(PANYNJ 2003)
Public Address System Announce

Public Address System Announce

WTC 2, After 9:03 a.m., cont’d

~9:20 a.m. –

Announcement made updatin

the condition of the building and progress oevacuation.Prior to approximately 9:40 a.m. –

Building-

announcement instructing occupants to go dConclusion:

Announcements in WTC 2 were heard b

building-wide before 9:03 a.m. and were least the upper regions (including above area) of WTC 2 after 9:03 a.m.
Evacuation (WTC 1) Evacuation (WTC 1)

• Occupants of WTC 1 overwhelmingly initiate

evacuation. The NIST Investigation found npublic address system announcements were occupants of the building, although the fire cwas attempting to make announcements.

• The NIST Investigation found no evidence to 

anyone who was above the 91st floor in WTairplane impact survived. This was due to thstairwells and elevators were destroyed and rescue, despite several attempts by both occaircraft, was not possible. 
Evacuation (WTC 2) Evacuation (WTC 2)

• In WTC

2, approximately 75 percent of the o

the 78th floor at 8:46:30 a.m. had successfubelow the 78th floor prior to the airplane impa.m. 

• Self-evacuation and use of elevators for 16 

2 saved roughly 3,000 lives.

• The decision to establish the primary evacua

underground through the Concourse (mall) astreet level by WTC

5 (commonly recalled a

Borders Bookstore) prevented a significant ninjuries and/or deaths.
Recommendations, Group 5: Recommendations, Group 5:

Improved Building Evacuation Improved Building Evacuation

Building evacuation systems should be improve system designs that facilitate safe and rapid  methods for ensuring clear and timely emerg

communications to occupants,

 better occupant preparedness for evacuatio

emergencies, and

 incorporation of appropriate egress technolo