World Trade Center Evacuations

Transcription

1 Lecture Overview World Trade Center Evacuations Rita Fahy Two studies of the World Trade Center bombing - 9/11 attack Difference in methodologies for studies Findings Lessons learned Two events 1993 and bombing Six deaths Buildings reopened several months later 9/11 attack Almost 3,000 deaths Total collapse of both towers Questionnaire survey of the members of the fire safety team Several human behavior studies, beginning with an analysis of first-person media accounts February 26, 1993

2 Summary of the 1993 Event Explosion in the underground garage Damage from bomb Fire confined to vehicles Emergency communication systems damaged Power interrupted Smoke and dust migration to all floors Total evacuation in both towers 6 people killed, more than 1,000 injured Evacuation Procedures Each tenant had at least one Fire Warden - Multi-story tenants had one on each floor 25 fire safety directors coordinated the activities of the fire wardens Two Port Authority employees supervised the fire safety directors Two fire drills required every year Drills did NOT involve actual evacuation Study Objectives To understanding the interaction of human behavior, the physical environment and the products of combustion through space and time To identify escape routes used by occupants To document smoke and other hazardous conditions observed by occupants and their perception of the threat To develop findings of significance to fire safety procedures in similar occupancies and for related fire safety educational effort Study Design Surveys were sent to 1,598 fire wardens and members of the WTC fire safety team Questionnaires were based on Prof. John Bryan s work at the University of Maryland Survey Population by Age Group Age Group Other Total % 39 28% 7 35% % No answer Total

3 First cue of something unusual? Heard/Felt Explosion 38% 27% Power/Phone Off/Flickered 5 11 Saw/Smelled Smoke 4 6 Told by Others 5 3 Explosion and Power Off Explosion, Power Off and Smoke 6 5 Explosion and Smoke/Dust 11 7 Initial perception of seriousness Not at all serious 7% 14% Only slightly serious Moderately serious Extremely serious Explosion 84% 74% Loss of Power 40% 53% Actions taken Call the fire department? 12% 21% Pull the fire alarm? Call switchboard? Call friends or relatives? Significant Findings Occupants in Tower 1 were more likely to alert others or report the event Occupants in Tower 2 were more likely to seek information and wait Men in Tower 1 were more likely to investigate than women in Tower 1 Experience during incident Did you hear the fire alarm? No 96% 95% Yes 3 4 Don't remember 1 1 Did you move through smoke? Yes 94% 70% No 6 30 Delay times to leave the building Time from Awareness of Something Unusual until Leaving Range 0-4 hrs 5 min 0-3 hrs 27 min Mean 15.3 min 34.7 min Median 10 min 15 min Time from Awareness of Fire until Leaving Range 0-4 hrs 5 min 0-3 hrs 5 min Mean 11.3 min 25.4 min Median 5 min 10 min

4 Delay time to attempt to leave Time from Awareness of Something Unusual until Attempt to Leave Range 2-30 min 10 m - 4 hrs 14 m Mean 8.9 min 39.9 min Median 8 min 25 min Time from Awareness of Fire until Attempt Range 0-5 min 0-4 hrs 14 min Mean 2.3 min 35.6 min Median 2 min 15 min How long to leave the building? Less than 5 minutes 1% 1% 5 to 30 min min. to 1 hour to 3 hours Over 3 hours 9 1 Note: This was meant to capture travel time, excluding stops and delays. During previous drills, did you Evacuate? Move? Evacuate? Move? Always 6% 5% 2% 1% Usually Sometimes Never Stairwell Interruptions Drawn from memory not accurate disposition or measures.

5 Improvements after 1993 A fire command post in each tower Improved voice communication on each floor Photoluminescent paint and signs in stairs Second power supply Battery pack on lights in stairs Drill every 6 months with staff training Evacuation chairs for each disabled staff Some Conclusions Significant difference in the perception of the incident severity between occupants of the two buildings; no significant difference in sex, age group or floor for occupants of the two buildings People are prepared to move in smoke, even if they think they may be heading toward the fire People need to be educated about basic fire physics if they are expected to react safely during a fire incident Training is needed for everyone not only Fire Wardens Numerous altruistic behaviors observed September 11, 2001

6 WTC1 was hit at 8:46, impacting floors 94 to 98. Occupants had 1:42 to evacuate before collapse. WTC2 was hit 16.5 min later. WTC2 was hit at 9:03, impacting floors 78 to 84. From that time, occupants had 56 minutes to evacuate the tower. Occupancy Towers designed for over 100,000 workers (Yamasaki, 2002) USA Today estimated 10-14,000 occupants - Mayoral primary election - New York Stock Exchange still closed - First day of school in some elementary schools - Work starts at 9-9:30 According to media reports: USA Today estimated that 5,000 to 7,000 people were in each tower. (est. 1/4 of the employees were at work at the time) Nobody above the floor of impact in Tower 1 survived Four people above the floor of impact in Tower 2 are known to have survived 99% of occupants located below the impact points in the towers survived Methodology Immediately following the event, started collecting first-person accounts from television, radio, newspapers, magazines and websites 280 accounts collected in 3 months 745 accounts over 18 months from 465 individuals 435 survivors accounts from WTC 1+2 retained for analysis

7 Study Population 435 survivor accounts Age range: 20 to 89 years old 118 women, 314 men, 3 not reported 251 in WTC 1 (North Tower) 184 in WTC 2 (South Tower) Methodology Create a questionnaire to interview each account: What was the first cue perceived of the event? Where was the person when s/he perceived that cue? What was the person s knowledge of the situation when starting the evacuation? How serious did the person judge the situation at first? Example of questions used Gender of survivor Age of survivor In which building was the person at the time of first cue? On what floor was the person? What was the first cue of event? How long did the person take to start evacuation? Who helped person during evacuation? Did the person delay start time? 33 questions in total Methodology Create a descriptive matrix Create a coded matrix - Develop a coding manual - Merge different accounts from the same survivor Conduct statistical analyses on data Account content analysis Two reviewers interviewed each of the 745 first-person accounts Compared two reviewers findings and resolved disparities Responses gathered in a qualitative database Accounts from same individuals were collapsed into one total of 435 accounts Responses were coded Study Objectives Gain an overall understanding of the circumstances surrounding the occupants evacuation, Gain insight into the variability of human behaviour and response time, Develop findings that could guide future research.

8 Why analyze media accounts? Some contained a high level of detail interesting to fire safety researchers Some of the information was gathered very soon after the event, preventing contamination Two years after the tragedy, no systematic research strategy to interview survivors was in place Limitations in using media accounts Questions asked of survivors are unknown, can be different from each journalist or with each interview Most dramatic stories get published Information might be left unreported Not a random sample * Individual experiences cannot be generalized to the whole population Tower 1 (North Tower) From impact at 8:46 to collapse at 10:28, occupants had 1 hr 42 min to evacuate Airplane impacted floors Prompt time to start for occupants below impact Crowding started around floor 30 3 staircases not used proportionally Strong smell of fuel Water in stairs on lower floors Not aware of events of Tower 2 No lights on some floors Tower 2 (South Tower) From Tower 1 impact at 8:46 to Tower 2 collapse at 9:59, occupants had 1 hr 12 min to evacuate Airplane struck building at 9:03, time left - 56 min Airplane impacted floors Start times varied Voice communication message was followed by some (few) occupants Crowding started around floor 50 3 staircases not used proportionally. Stair A unobstructed from top to bottom but used little 4 survivors above the impact zone Water in stairs on lower floors Contributors to successful evacuation on Sept 11 Low occupancy Overall good conditions on floors and stairwells Very strong initial cues Limited delay to start evacuation Occupants remained calm Training and past experience Rescuers and co-workers helped disabled and injured Towers design: sign system, lighting, stair integrity, discharge inside building

9 Initial location Means of egress used WTC 1, N=251 WTC 2, N=184 Upper floors (77 th - 90 people (36%) 94 people (51%) 110 th ) Mid floors (43 rd -76 th ) 79 people (31%) 57 people (31%) Lower floors 58 people (23%) 28 people (15%) (Basement - 42 nd ) Elevator 22 people (9%) WTC 1, N=202 WTC 2, N=158 Stairs 198 people (98%) 114 people (72%) Elevator 1 person (0.5%) 18 people (11%) Stairs & Elevator 3 people (1.5%) 26 people (16%) Location not specified 2 people (1%) 5 people (3%) First cue of event reported Time to start evacuation First Cues WTC 1, N=212 WTC 2, N=145 Audio cues: heard explosion, crash, 107 (50%) 69 (48%) rumble Visual cues: saw fire, incoming plane, 87 (41%) 96 (66%) debris, smoke Building movement: felt building sway, 146 (69%) 30 (21%) tremble, jolt Contents movement: furniture 66 (31%) 11 (8%) movement, ceiling falling Warning from others 14 (7%) 34 (23%) Impact 29 (14%) 1 (1%) Frequency Immed Shortly Delayed Stayed Stuck Start Time WTC 1 WTC 2 Smelled fumes or felt heat 12 (6%) 16 (11%)

10 Conditions on floor at impact Obstructions encountered 80 WTC 1, N=134 WTC 2, N=57 Debris (collapse) 72 (54%) 38 (67%) Smoke 74 (55%) 25 (44%) Fire 41 (31%) 20 (35%) No power, dark 20 (15%) 18 (32%) Smell of fumes 13 (10%) 7 (12%) Dust 9 (7%) 10 (18%) Water 7 (5%) 3 (5%) Door jammed 7 (5%) 2 (4%) Crowds, people injured 2 (1%) 7 (12%) Trapped 5 (4%) 2 (4%) Percent Door jam Debris Crowds Smoke No power Trapped Fire Obstruction WTC 1 WTC 2 Announcement in WTC 2 Announcement made at approximately 9:00 (struck at 9:03) Of 184 WTC 2 survivors, 96 (52%) mentioned hearing message 69 (72%) decided to disregard the instructions 16 (17%) remained in their offices or decided to turn back Occupants with disabilities or injuries 27 reported a disability (6%) -All were helped by co-workers and rescue officers 47 were injured that morning (11%) -Some with extreme injuries who were mobile exited faster than the majority -All were helped by co-workers and rescue officers Knowledge of situation N= had high level, saw plane, heard of terrorist attack 214 had moderate level, speculated about bomb, saw debris outside 47 had low level, didn t know what was happening Influence of others N= influenced by authority figure 97 influenced by co-workers 66 stated they took a leadership role, (52 men 14 women)

11 Perception of others N= said others were calm and orderly 84 said others were upset, crying, nervous, anxious 78 said others were momentarily panicked, pushing, shoving Impact of 1993 N=41 3 said 1993 motivated a quick start 5 said they now had evacuation kits 4 survivors mentioned photoluminescent marking in stairs 1 mentioned evacuation chair Time out of towers 8:48 9:02 a.m.(before WTC 2 impact) WTC 1, N= 211 (impact - 8:46) (collapse -10:28) :03 9:30 a.m :31 9:58 a.m.(before WTC 2 collapse) 9:59 10:27 a.m.(after WTC 2 collapse) 10:28 a.m.(after WTC 1 collapse) WTC 2, N= 183 (impact - 9:03) (collapse - 9:59) Conclusions First-person account content analysis is a valuable, timely method to document a major incident, although findings cannot be generalized. Large number of detailed accounts found from survivors who were in different areas, allowing us to gain insight into the event. Conclusions (continued) 44 WTC 2 survivors (24%) used elevators to evacuate 96 WTC 2 heard the announcement, 69 (72%) decided to disregard the instructions - Judgment of situation - Commitment to the decision to leave People who experienced 1993 left immediately Conclusions (continued) Overall, impression of calm and order during the evacuation Presence of emergency crews reassured evacuees Counter-flow movement on stairs by emergency crews did not prevent occupants from evacuating

12 Comparison to 1993 evacuation Cues to situation: Ambiguous in 1993; powerful and multiple on 9/11 Stairwell conditions: Smoky and dark in 1993; lit and clear on 9/11 Evacuation time: 6 hours in 1993; 1:42 on 9/11 Impact on the Public Perception Perception of risk in high-rise structures Fire safety in high-rise structures Phased evacuation / Protect-in-Place Potential collapse of buildings under fire conditions Reluctance to follow instructions Reluctance to serve as fire wardens Calm, orderly and altruistic behavior observed in both Lessons learned - improvements made in egress system helped - training was more complete - people were calm and altruistic - movement continued under difficult conditions 9/11 WTC Evacuation Studies Analysis of first-person accounts in the media Small questionnaire survey Aug 2002 CDC/Columbia University interview study NIST investigation UK joint university study Also a study on deaths below impacts