Human Behaviour - How efficient are modelling systems?
Attempts to predict the reactions of occupants in buildings equipped with new systems such as fast detectors, smoke extractors or residential sprinklers will fail if the complexity of human behaviour is not taken into account. To achieve this, it is necessary for fire safety engineers and psychologists to work closely together.
For decades, fire safety engineers have successfully designed and installed fire safety systems in buildings.
Even though adequate systems are installed, failures still occur. In some cases, problems arise because the fire safety systems were developed on the basis of misconceptions about occupants' behaviour. For example, well designed and installed fire doors have failed to fulfill their role in office buildings because occupants use door stops to facilitate free flow of people. Thus, in the event of a fire, the doors stay open. Had fire safety engineers collaborated more with behavioural scientists, this dilemma could have been foreseen. Further, it is often people's lack of knowledge about fire safety that contributes to tragedies, as confirmed by recent findings.
Discussions with people who have experienced a fire emergency and with evacuation drill participants have shown that most people knew they should not use an elevator during a fire. Most, however, had little idea why its use is dangerous. Some mentioned the possibility that elevator cables would burn and the elevator car would fall to ground level, but none cited the possibility of smoke accumulation in the elevator shaft.
In another example, some residents mentioned that in fleeing a fire in their apartment, they felt there would be no point in closing their apartment door since the door was made of wood and wood burns easily. These statements, though rational, are based on insufficient knowledge about the evolution of a fire.
People's Reactions During Fires
This lack of knowledge about fires on the part of building occupants has a parallel in the misconceptions fire safety engineers have about people's reactions when faced with a fire.
The notion that people caught in a fire will panic and stampede has long been rejected by psychologists. Panic has rarely been observed as a human response to danger from fire. In fact, most people appear to apply rational decision-making relative to their understanding of the event at the time of a fire.
It has often been observed that occupants -- in the initial moments of a fire, upon smelling smoke or hearing the fire alarm -- do not react; they deny there is danger or they ignore the situation. This seems especially true in public buildings where occupants do not want to be seen to overreact to a false alarm or to a situation that is already under control. Such avoidance behaviour in a dangerous situation often results in a delayed start to evacuating a building or taking protective action. It is paramount to consider this delay in assessing the risk to occupants' lives in a building.
People Are Fearless of Smoke
In the past, it has been assumed that people were afraid of smoke and would flee upon smelling it or seeing it. A different picture, however, has clearly been demonstrated on numerous occasions. During the evacuation that followed the bombing of the World Trade Centre in New York City, people entered smoke-filled staircases and travelled through smoke for extended periods of time. People were evidently unaware of the dangers of moving through smoke and the rapidity with which its toxic components could harm them.
This is a case where people's behaviour must be altered through education and training. But there is more to it. It is also imperative to create fire safety systems that keep common escape areas free of smoke for as long as possible. This appears especially important in such large public buildings as arenas and shopping centres where occupants are likely to delay their evacuation until they are instructed to leave.
Drawbacks with Computer Models
Many fire safety engineers use computer models for testing various designs as part of decision-making. Models on fire growth and smoke spread are commonly used, as are a few dealing with occupant evacuation. Most of these evacuation models, however, are flow models for the movement of occupants and rarely include an appreciation of human behaviour. For example, in some such models, occupants are assumed to systematically leave by the shortest route, even though it is well known that distance is only one of the parameters; another, among many more, is the choice of an egress route.
A recurring misconception built into some evacuation models is that people's movement is analagous to water flowing through pipes or balls moving on a pool table. Physical flow models are misleading, because they assume that people move like unthinking objects. Instead, to more accurately represent real behaviour, acceptable evacuation models should include, for example, the possibility of movement in a familiar direction, turning back, moving toward the fire and moving at different speeds.
Importance of Occupant and Building Characteristics
Behavioural scientists have found that occupant characteristics are significant determinants of safe evacuation in a fire emergency. Gender, age, alertness, mobility and training are some of the important factors that affect evacuation time and the manner in which occupants deal with an emergency. The occupants' situation in an emergency is also important: whether the occupant is alone or in a group, is a staff member or a visitor, or is active or passive, all have particular connotations.
No less important are the building's characteristics: its design, organization and fire safety system have an influence on the evacuation outcome. How easily an occupant can find escape routes and understand signs and instructions depends on the way-finding performance of the building.
The stage of fire development also has a major impact on occupants' behaviour. Smelling or seeing smoke or having to turn back because of smoke and heat often explain the reactions of occupants.
The design of a fire safety system cannot be universal, nor can it be applied indiscriminately to all buildings of the same type or occupancy. Ideally, a fire safety system should be tailored to the characteristics of the building and its occupants. For a long time, fire safety systems in multi-unit residential buildings were planned with two parents and two children per apartment in mind. Through the years, this occupant profile has changed tremendously. Nowadays, these buildings are mainly occupied by single-parent families and an increasing number of elderly people living alone. These changes must be taken into account in developing a fire safety system for a building.
Conclusions
Notwithstanding the difficulties in describing, explaining and modelling human behaviour when people are threatened by fire, significant results have emerged from recent research. These results have been essential in the development of successful safety training programs and in the implementation of new fire safety systems, such as using public address systems to give instructions, thus reducing the time needed to start an evacuation. There is, however, much to be done to improve safety in all buildings. New engineered systems, such as fast detectors, smoke extractors or residential sprinklers, which could reduce the risk to life, are constantly being developed.
Attempts to predict the reactions of occupants in buildings equipped with these new systems will fail if the complexity of human behaviour is not taken into account. A good starting point is to proceed from what is known and develop fire safety systems that incorporate this knowledge. To achieve this, it is necessary for fire safety engineers and psychologists to work closely together. A collective effort should help achieve the common goal of improving fire safety in buildings.
Dr. Guylene Proulx is a fire research psychologist at the National Research Council's Institute for Research in Construction. This paper is a contribution from the National Research Council of Canada, Institute for Research in Construction.
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