Fire Dynamics Design, Steel Glazing Systems, Architecture Article
Fire Dynamics & Human Behaviour
Safe Architecture: Architectural Discussion by Wrightstyle – 2 Oct 2012
2 Oct 2012
Fire dynamics and human behaviour
Article by Wrightstyle
Our business at Wrightstyle is based on a fundamental understanding of fire dynamics, and how to design steel glazing systems to provide safe evacuation routes in a fire or terrorist incident. While providing those safe exits remains fundamental to fire and building safety, human behaviour in an emergency situation can also be an important factor.
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 and built. 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 in 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.
In other words, computer modeling can only take us so far in designing in safety. What is also needed is an understanding of human behavior 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.
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 call to New York. 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 an occupant takes the alarm 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 occupants 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 out 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.
What it means for building designers is to design in human nature, using behavioral science as well as computer modeling. We’ll leave the psychology to the experts, but our steel glazing systems – doors, screens, and curtain walling – can provide up to 120 minutes of fire resistance, protecting against fire, radiant heat and smoke.
Our compatible systems, with the glass and steel framing systems tested together, are accredited to EU, US and Asia Pacific standards. 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.
Fire dynamics and human behaviour article information from Wrightstyle