Jason D. Averill, Project Leader

Building and Fire Research Labo

National Institute of Standards and Tec

U.S. Department of Commerce

jason.averill@nist.gov

Federal Building and Fire Safety Inv

of the World Trade Center Disa

World Trade Center Investigatio

Project 7: Occupant Behavior, Egr

Emergency Communication

June 23, 2004
Project 7 Staff Project 7 Staff

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 McGuckiJon 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
Collection of Occupant’s First Pers

Collection of Occupant’s First Pers

• Face-to-face Interviews

• Over 225 Occupants of WTC 1, 2, and 

• Telephone Interviews

• 803 Occupants of WTC 1 and 2

• Focus Group Interviews

• 6 Focus Groups
Other Activities Other Activities

• Other Data Collection

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

• Causal Modeling• Egress Modeling• Observations of Fire, Smoke, and Damage
September 11, 200

Moments Before 8:46 a
Building Population Building Population

Total 8,900 8,500 

Total Building Population

599*** 1,434 Decedents ***

Number of Decedents

Standard Error (Total) 750 900 

Standard Error (p) 1.90% 1.92% 

Sample n 427 376 

Statistical Precision Calculations

7,500** 7,900 

Estimated Total Population of Survivors*

WTC1 WTC2 

* 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

Maximum 73

Minimum 22

Median 46

Mean 45

Refuse 1

N Valid 439

Maximum 74

Minimum 21

Median 44

Mean 45

Refuse

2

N Valid 361

WTC 1

WTC 2

1975

1976

1977

1978

1979

1980

1981

0.0%5.0%

10.0%15.0%

20.0%25.0%

Percent

1975

1976

1978

1979

1980

1981

0.0%5.0%

10.0%15.0%

20.0%25.0%

Percent

Age

Years 
World Trade Center Occupant Prep

World Trade Center Occupant Prep

• During the year from Sept. 11, 2000 to Sept

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.
“I saw the plane halfway in the building.” 

(90’s)

“The door blew open from the closet, 

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

“We felt the entire building shake and saw 

some people who were sitting in chairs slide across the 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. I saw a brown cloud coming down the center corridor in the lobby, and I feared for my safety. The brown cloud had a heavy density and reached from floor to ceiling. It looked to me like it was both smoke and debris. It first came from the center corridor, but by the time it reached the revolving doors (a split second later) it seemed to come from every direction. At this point, the revolving doors exploded They seemed to vaporize.” (Concourse)

Data consistent thOnly small numbe

and smoke at 

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

WTC 1 - Fir

WTC 1
WTC 2

“I saw the plan

(100’s)

“I noticed it wa

saw massivflames wraaround the 

“My boss came 

evacuate.” 

“I heard a loud 

Saw smoke, flame, or debris 16%Other 6%Saw airplane 3%By other person (face-to-face, 14%telephone)Heard something (boom, 51%crash, explosion, rumbling)Felt something (building 11%moving, impact, shaking, swaying)

WTC 2 – First Awareness*

*Primarily from Tower 1

Observations vMany observa

debris
September 11, 200

8:47 a.m. – 9:02 a.m
Time to Ev

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. (90’s)

“To me everything seemed 

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

“I was close to the windows. The 

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

WTC 1
WTC 2

“We were instruc

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

“Heard the build

announcemethe stairs to eto a uniformedoor open in lobby. We westairwell area elevators to gkept on going (80’s)

Time to Evacuation Start (min)

0 20 40 60 80

Percent Beginning Evacuation

05

1015202530

WTC 2 Hit

WTC 2 Collapse

• 91% began evacuating before Tower 2 was hit; 22% within one minute of WTC 1 impact.• 41% of the survivors exited the building before WTC 2 was hit.
“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.” (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.” (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.” (60’s)

Interim Period 63% 52%

Initial Awareness 48% 41%

Life in Danger? Others Self

Other activities Continued workShut down comFought fire or smMoved between Talked on telephSearched for othHelped others Gathered persoTalked to others 

Activities Be

WTC 1
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.” (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” (100’s) – Decision was made to use stairs until the PA announcement, when respondent used an elevator to evacuate.

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

Initial Evac

Did not consider el

•“I knew one selevator in an situation” (30’s
September 11, 200

9:03 a.m.
Some noticed minor 

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

“I felt the air clear 

gush of wind tsmoke (this habuilding 2 was (60’s)

“The building sho

the first time [bstopped briefly 

(60’s)

“Very soon after e

someone with communicatioword that a cothe building. Lclarified as to Later [there wsecond plane 

WTC 1

“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 attack.” (40’s)
•“It was clear that something hit the 

building...the stairwell swayed and it was as if the building was doing the ‘twist’.” (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.” (70’s)•“I heard a loud noise, felt the building shake, and the temperature in the air went up.” (60’s)

WTC 2

Sprinklers Extreme hFatally injpeople Fire alarm Fire or flaCollapsed Smoke Jet Fuel Fallen CeiPower out

Observa

Still o
September 11, 200

After 9:03 a.m.
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 of Survivors Exiting

Time Since WTC 1 Attack (min)
September 11, 2001 September 11, 2001 WTC Evacua

WTC Evacua

WTC 2 3.1 1.3 0.2WTC 1 1.4 0.3

A

B

C •A – Elevator use d

compared to stairs •B – Exit rate simil•C – Rate slows ~ collapse for WTC 

0

102030405060708090

100

0 10 20 30 40 50 60 70 8

Time Since WTC 1 Attack (min)

Cumulative Percentage (%)

WTC 2 Hit WTC 

WTC 2

WTC 1
Reported Aids & Constraints to E

Reported Aids & Constraints to E

10% Floor Warden 13%

11%

Photoluminescent 

18% paint

32% Exit signs 35%

44% Firefighters/Police 30%

60%

Support from 

66% others

WTC 2

Evacuation 

WTC 1 Aids

Bad/m

5% sig

11% Poor 16% Locke

Lack 

24% instr

51% Firefight

Cro

73% stai

Evac

WTC 1 Cons
Causal Modeling: WTC 1 Causal Modeling: WTC 1

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

Environ’l

Cues

Floor

Obtained

Info.

Perceived

Risk

Sought

Info.
Causal Modeling: WTC 2 Causal Modeling: WTC 2

The main process that led to evacuation delay:Environmental cues and 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.

Environ’l

Cues

Floor

Obtained

Info.

Perceived

Risk

Sought

Info.
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 Moveme

0

20406080

100120140160

0 5000 10000 15000 

Number of occupa

Evacuation Time (min)

8,800 - 9/11 capacity
Findings and Conclusions Findings and Conclusions

• Total Building Population at 8:46 a

September 11th:

• WTC 1: 8,900 ± 750• WTC 2: 8,500 ± 900• Twin Towers: 17,400 ± 
• At 9:03 a.m., when WTC 2 was hit, 21% o

exited WTC 1 and 41% of survivors had e

• By 9:37 a.m., 22 minutes before collapse

survivors had exited WTC 2. 

• At 9:59 a.m., when WTC 2 collapsed, 88% 

had exited WTC 1.

• By 10:12 a.m., 16 minutes before collaps

survivors had exited WTC 1.

Findings and Conclusions, Cont’d Findings and Conclusions, Cont’d

• Approximately 87% of WTC occupants, and 

those below the floors of impact, were able tsuccessfully evacuate.
• Self-evacuation, use of elevators for 16 

WTC 2 saved roughly 3,000 lives.

• During the last 20 minutes before each b

collapsed, the evacuation rate in both buslowed to about one-fifth the immediatelevacuation rate. This suggests that for t

and able to reach and use the undamagstairways, the egress capacity (the numof exits and stairways) was adequate to survivors.

Findings and Conclusions, Cont’d Findings and Conclusions, Cont’d
• Preliminary results from application of existin

egress models for a full capacity evacuation WTC tower with 25,000 occupants and visitomovement time of 2 h and 15 min. Given thaevacuation time on September 11, 2001 was without elevator use, a full capacity evacuatitowers with 25,000 people would have requi(2.5 times 100 min). To achieve a significanevacuation at full capacity would have requiregress capacity (number and width of exits a

Findings and Conclusions, Cont’d Findings and Conclusions, Cont’d