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Fire dynamics and human behaviour

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Building safety is largely determined by taking a multi-disciplinary approach to assessing hazards – from power failure to cyber attack, from civil disorder to fire and explosive detonation – and arriving at risk assessments that illuminate how that building should be designed, built or managed. However, psychology is also a potent element.

Evacuation models, based on engineering and computational tools, have been used for some time to estimate the time taken to evacuate a building. These models, particularly for larger or more complex buildings such as hospitals, are a requirement of fire safety and building approval. But research at the US National Institute of Standards and Technology (NIST), among others, demonstrates that those computer models don’t necessarily reflect the variable nature of human reaction.

It all seems deceptively simple. A fire alarm sounds in an office building and everyone reacts promptly, only using designated stairways and exits, and making their way outside in a brisk but orderly manner. That is how a computational model might simulate a fire situation. But it doesn’t consider what is termed “exit choice behaviour” – the different exits that people will choose to leave by, often because they’re also the entrances and routes by which they arrive at work.

Nor does it model “pre-movement times” – the golden period immediately following a fire alarm, when the fire has been detected but doesn’t yet pose a threat. Some members of staff will assume that it’s yet another fire alarm test. Others will assume that it’s a false alarm, maybe because they’ve happened before. Others will choose to ignore it because they’re making an important telephone call, or may have mobility problems. Others might not want to appear fearful in front of colleagues.

The psychology at work is that a fire alarm in itself is not necessarily regarded as an immediate call to action. It may be an alarm, but it’s not alarming. The alarm may have sounded, but no threat is apparent. There is no visible fire and no detectable smoke. We know that the chances of it being a real fire are remote and, mentally, we are hot-wired to think logically. Reason tells us that the situation is unlikely to be dangerous: therefore, there is no need to evacuate.

However, even when the alarm is taken seriously, it’s also a source of confusion, because the alarm is simply a loud noise. It doesn’t indicate the location of the fire, or how serious it might be. Psychologically, that confusion also adds to a delayed flight response: most of us instinctually delay responding to a threatening situation until the danger is well understood and, therefore, what our strategy should be to avoid it.

It adds up to a building evacuation that may be greatly delayed, or patchy in nature: some occupants taking the fire alarm more seriously than others. However, recent research indicates that this “pre-movement time” is a more significant evacuation factor than the length of time taken to reach an exit. As much as two-thirds of the time it takes people to exit a building after an alarm is start-up time – time wasted in looking for more information.

But it’s when danger does become apparent that the psychology becomes more complicated. For example, if someone encounters smoke during their evacuation, will he or she choose to go through it, even if they know it’s the quickest route to an exit? Research indicates, although not conclusively, that the majority of people will be disinclined to move through smoke if it seems to them to be “thick” or “black” – or if there is very limited visibility. There may also be an assumption at play that there’s no smoke without fire. (Leaving aside the fact that smoke kills more people than fire).

There are other factors at work, such as familiarity with the escape route: research suggests that people are often more likely to use a familiar exit that is further away than an unfamiliar exit nearby – again increasing evacuation times. This was often attributed to panic, although social scientists now seem to agree that seemingly-irrational flight behavior to an exit is perfectly rational: they are rationally seeking an exit with which they are familiar.

Group dynamics also plays a part; how a number of people, in different states of fear, influence one another. Evidence suggests, for example, that people evacuate buildings alongside colleagues with whom they have an emotional attachment. In a shopping centre that social dynamic may be familial, with parents trying to control small children. How does the family group react, when each member is instinctively responding in a different way?

All of those factors, and many other variables, can influence how levels of protection should be applied within buildings: not only to calculate the time it will take to evacuate along designated or undesignated routes, but to also build in additional time to allow for the elderly or infirm, or the simply complacent. Those escape routes – even if they’re not designated escape routes – and the likely numbers of people using them, will also have an impact on the size of intermediate and exterior doors.

To illustrate how far this multi-disciplinary science has come, an international symposium on the subject last year in Cambridge, UK was submitted with 43 technical papers and 20 poster papers, with panel sessions attended by delegates from around the world. The symposium also focused on two areas: life safety options for people with disabilities, including the elderly, and fundamentals of egress calculations for life safety assessments.

Getting it wrong can have terrible consequences, as a major study found on the evacuation of the World Trade Center, a multi-year qualitative and quantitative research project by the Mailman School of Public Health at Columbia University and CDC.

It found that people involved cited four factors that affected their decision to begin evacuating. One, a perceived ability to walk down multiple flights of stairs. Two, experience in evacuation of a WTC tower, including knowledge of stairwell locations and whether individual stairwells led to street level exits. Three, concern over leaving their work areas without the approval of executives or managers; and, four, information regarding what had occurred, what floors were involved, and how to respond.

Assumptions can be built into the evacuation model that are too optimistic or, at the other end of the scale, too conservative, leading to additional risk or cost. In other words, computer modeling can only take us so far in designing in safety. What is also needed is an understanding of human behaviour in an emergency situation, particularly the factors that have been shown to influence our decision-making processes. By understanding those factors and processes, a fire safety team can develop a more comprehensive – and predictive – behavior model for a building’s fire evacuation.

The qualitative data also suggested that, after a decision to evacuate was made, many people stopped to attend to last-minute activities – for example, making telephone calls, shutting down computers, or gathering up personal items. Deciding which route to take, stairs or elevators, might have delayed evacuation progress for others.

Progress was also reportedly slowed for others because of their poor physical condition or inadequate footwear. It provides a stark example for building designers, working with other professionals, to use behavioral science as well as computer modeling to design in human nature and develop better and more predictive evacuation models.

As a company that understands fire dynamics, our strong advice is to always specify the glass and steel as one unit. In a real fire situation, the glass will only be as protective as its frame, and vice versa. Specify each component separately, and you run the risk of one failing – and therefore the whole fire protective barrier failing.

Fire can be friend or foe. Controlled, it can warm us and cook our food. Uncontrolled, it can be extremely dangerous, and the safest strategy is to move away from it as quickly as possible. That’s what fire alarms are meant to warn us to do, even if human psychology delays our response times. It makes our advanced glazing systems even more important, containing fire away from escape routes, and giving everyone more than enough time to escape.


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