There are a number of influences which affect response to an emergency, among them are cultural influences and training.

Several examples from countries where there is a strong hierarchical background and a culture of obedience to authority figures demonstrate that systems and procedures which work very well in less structured societies may not be workable in a rigidly obedient workforce.

An example of such a case occurred in a factory in the Far East where over a hundred workers remained at their workstations because they had been ordered to do so and refused to attempt to escape until far too late because they were afraid they would lose their jobs if they disobeyed the manager.

Globalisation has meant that the competition to create attractive working and corporate investment environments has seen the spread of modern structures, including many ultra-high rise structures into countries where the local experience and culture is not fully attuned to the niceties and assumptions of the building code used by the designer.

In some instances, designers have had to employ extremely innovative concepts to address the issues of evacuation and provide for the safe exit of the occupiers in very large or very tall structures. As a result, there are now buildings in use – and under construction – which rely on protected links to adjoining towers which form part of the same building and lifts (elevators) installed in protected cores which may be used for evacuation as well as the traditional protected staircases.

All of these require a high degree of understanding of the relationships between the passive structural protection, the active protection systems and the active understanding of the building users of their use. Familiarisation with the evacuation procedure and the routes to be used are vital if these innovative solutions are to be effective – and that must take account of the norms of the society in which the building operates.

One of the things which stands out in several disasters is that frequently those who survive them did not obey “normal” instructions, and this has a major impact on the evacuation of very large numbers of people.

Among the many interviewed after the Twin Towers event, there were numerous examples (particularly among those escaping from above the impact points) of people having been told to “stay put” and await instructions, and who then carried out their own investigation and, in direct defiance of the instructions, started to evacuate themselves and their people.

This behaviour is also evident in the Piper Alpha disaster in the North Sea, where the “rule breakers” survived by jumping into the sea from the platform, while those who waited for the evacuation instruction didn’t.

Evacuation models and procedures vary according to the building construction, its use and the occupants’ needs. The simplest of these is the Total Evacuation model in which everyone is immediately required to leave the building by the nearest exit on the alarm being sounded. While this may appear straightforward, it is not always so. The human factor can create a number of difficulties, not least being the fear of looking foolish or of being blamed for having taken an action which results in financial loss for an employer, such as cutting off a process which is costly to restart or cannot be restarted without an expensive resetting of the equipment.

In large volume mercantile buildings such as shopping malls or department stores, the majority of occupants may not be familiar with the exit route and know only the mall itself and the entrance they habitually use to access the mall. This can be further complicated by the fear in some countries of pilfering which leads to all the ground floor exits being permanently locked. The author has several times encountered this in the Far East particularly, but it has a number of manifestations closer to home as well. When challenged, managers invariably claim that a “security” officer will unlock these in the event of a fire, but this writer has yet to find a single instance where the designated officer actually carries the required key.

In high rise situations it is common practice to adopt a phased evacuation model which calls for the total evacuation of the storey on which the incident has occurred with the two immediately above it and the one below it. The building can then be progressively evacuated, usually taking all the storeys above the fire first, storey by storey.

Received wisdom until recently was that the lifts should not be used at all unless these were “fire” lifts – and with good reason since the introduction of heat sensitive call buttons in the lobbies on each storey frequently meant that the lift would go to the fire floor and open its doors to the fire.

Where a building has been constructed without a lobby approach to the stairs, the staircase can be compromised by the firefighters who must pass their hoses through the door as well.

Mass evacuation presents a number of problems for the planner and the manager of fire safety procedures in any environment, but possibly none more so than where there are large numbers of people to be moved through exits with which they are not familiar.

Studies conducted over many years have shown that, to some extent, fluid dynamics apply when large numbers of people move along a confining space, be it a passage, mall or tunnel. These studies have also shown that if exits are wider than two metres, the discharge tends to slow down and the risk of stumbles, pushes, trips and falls occurring increases. It is for this reason that there are longitudinal barriers installed outside the exits for football and other stadia. It is used to control movement out of theatre exits as well, exploiting the instinct to keep moving until free of the restriction on direction and movement.

Many of those interviewed after escaping from the World Trade Centre identified the problem of initial uncertainty as to what had happened and what response would be appropriate. Contrary to the assumptions on which many guides for evacuation are based, the initial response is not to leave the building but to seek information and instructions, sometimes to make an individual assessment of the threat.

This response is identified again and again in research; notably that carried out by the late Jonathon Sime. It is a behaviour that is identifiable in the video footage recorded during the fire in the Bradford Football Stadium in the UK where many of the people in the grandstand could see the fire, could feel the heat from the smoke plume but did not feel immediately at risk and so failed to evacuate until the fire began to advance very swiftly toward them.

In very large and complex buildings, such as high rise structures, the sense of isolation on individual storeys is reinforced by the mental separations created by the fact that different storeys and even different compartments on the same storey militate against communication between groups. This makes the dissemination of essential information to all occupants difficult, particularly in instances where a major catastrophic event may have disrupted the emergency communications systems.

An issue which stands out from the survivor accounts and the police telephone logs of the World Trade Centre incident is the number of telephone calls made to the police and other services from people in the towers, seeking advice or instructions. This raises several questions, not least, the quality of the information available to them within the building or the absence of it. It is equally clear that an operator remote from the scene and unaware of the actual scope or nature of the emergency could not be expected to give the sort of instruction or information the callers needed to make informed and rational decisions.

It becomes clear that the initial responses by many occupants was to seek advice, or await further instruction and when this failed to be given, began to seek alternative guidance, with some turning to telephoning friends or other floors, television broadcasts and even local radio stations in order to obtain information.

The interview data suggests that around 20 per cent of the occupants made telephone calls in the pre-evacuation stages of the disaster, not to obtain information or to the emergency services, but to family and friends to reassure them that they were safe. This high percentage is in itself significant because it impacts adversely on the evacuation, seriously reducing the time available to escape. If this behaviour is typical, then it has serious implications for any future event in any of the new very tall structures currently being built.

A significant number (26 per cent) also reported that they collected either personal or work related items from their workstations, desks or offices before attempting to evacuate. In a significant number of cases this meant actually returning to a desk from some distance away and has a further impact on evacuation times.

Group behaviour is a major influence in situations where the occupiers may feel a high degree of uncertainty, and the group dynamics displayed in the WTC incident certainly support the view that within the towers decisions to evacuate were often taken “locally” and led by individuals who influenced groups, though once on the move, groups tended to expand and contract as other individuals joined or led parts of the group into a different route.

Once the evacuation began in earnest, the stairs were initially very congested in the upper storeys. The data available suggests that initially above the 44th Storey Sky Lobby in both towers the stairs were congested and movements slow, but this improved as people descended. It must be remembered that in a high rise building the staircases are generally designed, irrespective of the national code in use, to accommodate the evacuation of a maximum of four floors simultaneously. That is, the fire floor, the two above it and the one below it.

In the WTC towers, the nature of the incident and the number of affected storeys meant that this capacity was rapidly exceeded. Another factor may have been the behaviour of the early evacuees who proceeded down in single file allowing a clear “lane” in the stairway for the assisted evacuation of injured occupants. Obstructions did occur, frequently related to evacuees needing to rest and groups of firefighters and police officers trying to ascend. In fact it is now recommended that firefighter training include instruction in their taking regular rest breaks, outside the stairwell. In some instances evacuation is reported to have come to a complete halt while these groups moved upward. Evacuees also reported water spilling down the stairs and this further slowed their movement as the fear of slipping made people cautious.

A large number of those interviewed reported using the elevators to evacuate, though this appears to have been confined to areas some distance below the impact floors. Elevators can, in buildings designed for this use, be used successfully, but, as already identified elsewhere in this article, must be located in protected shafts and fitted with controls that do not permit the elevator to be called accidentally to the fire floor itself. In fact, such elevators need to be fitted with controls which require constant user operation to move the cabin or open the doors and release of the door control should immediately close the doors as a safety measure. In the WTC, certainly in the early phase of the evacuation, it would appear that the lifts were used in normal operating mode.

As can be seen from this study by the University of Greenwich Fire Safety Engineering Group, the lessons to be learned from the World Trade Centre have implications for the owners and users of large buildings everywhere. Key lessons include the need for better information to occupiers early in the development of an incident, better awareness and training for all occupiers and constant policing of the escape routes and exits. A significant number of the exits in the WTC towers were found to be locked or inappropriately secured, further hindering the evacuation. That said, the successful evacuation of over 12,000 people from the towers between the assault and the collapse speaks highly of the ability of occupiers to take the appropriate action when given the correct lead and stimulus.

References

Collection and analysis of emergency services data – evacuation of the World Trade Centre Towers 11th September 2001: Human Behaviour Data appearing in the mass media;   Fire Research Technical Report 6/2005; Prof E R Galea and Dr S Blake.
Collection and analysis of emergency services data - evacuation of the World Trade Centre Towers 11th September 2001: Analysis of the emergency services data;  Fire Research Technical Report 7/2005  Prof E R Galea and Mr A J P Dixon.

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