Lawrence Webster Forrest (LWF), Fire Engineering and Fire Risk Management Consultants
Lawrence Webster Forrest (LWF), Fire Engineering and Fire Risk Management Consultants



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Lawrence Webster Forrest
Legion House
Lower Road
Kenley
Surrey
CR8 5NH

Tel: +44 (0)20 8668 8663 Fax: +44 (0)20 8668 8583
E-mail: fire@lwf.co.uk

Human Behaviour in Fire

A major consideration in any fire safety design is human behaviour.  Failure to consider this aspect could lead to a failure in the design.  Therefore as designers and engineers, we must understand the likely actions people will take in a fire scenario to ensure their safety.

Understanding human behaviour in fire has required a multi-disciplinary approach, from engineers, psychologists, sociologists, architects and mathematicians to name a few.  Studying human behaviour in fire allows designers to anticipate likely reactions and therefore reduce the risk of fire posed to occupants.

Numerous factors that affects human behaviour have been studied, for example, ‘exit choice behaviour’ (i.e. when given a choice, which exit do occupants choose).  Prior to significant study, other factors that had not been considered to be important were found to be fundamental, for example, ‘pre-movement time’.  The time it takes from the alarm sounding, to the occupants initiating their escape has found to be very significant and in some instances, more significant than the distance travelled to an exit.

Research has also studied the actions of occupants when faced with smoke, for example, will occupants travel through smoke?  What levels of smoke will occupants travel through?  How do fire characteristics (such as heat and smell) influence escape?  Does familiarity with the escape routes have any impact?  The occupancy of the building will also have significant influences, for example in a shopping centre, there is likely to be significant social affiliations (family members, parents with children) this will affect escape behaviour and therefore escape time.

If we accept that fire safety can not prevent all fires and that fires will occur, our focus has to be set on time.  This is evident through all elements of fire safety design.  We provide fire resisting construction to prescribed elements, for example 30 minutes resistant enclosures to escape stairways and corridors.  We limit the distance travelled to an exit, as a method of limiting the time to escape.  The widths of doors and stairs is determined by the number of occupants they serve, to ensure people are not queuing to reach their escape, another method of ‘buying time’.  It is evident that the vast majority of requirements within design codes relates to time.  It is on this basis that we must acknowledge human behaviour as a factor of escape.  It is however noted that the uncertainties around human behaviour make definitive guidance difficult.  We can however consider all available data, both empirical data alongside research results to determine typical behaviour profiles.  Acknowledging a level of uncertainty should also push designers into ensuring levels of design redundancy and safety factors into their design.

The exact action of occupants will always be hard to predict due to the number of variables.  Individual differences within peoples perception of risk will have an influence as well as the actual fire event itself.  External factors such as frequent experience of false alarms will also affect occupants response.  Similarly, group dynamics and the actions of others will affect occupant behaviour.

Panic.  This word is used synonymously when discussing fire.  However, studies have shown that panic behaviour is somewhat different to what one might expect.  Panic, in fire is more akin to ‘flight’ behaviour, which is likely to be once the risk posed to occupants is severe, i.e. once occupants have a genuine fear for their safety, due to the cues of fire, heat, smoke, flames and is therefore more likely to be rational behaviour in terms of survival, rather than ‘blind panic’.

It is clear from this bulletin that this is a complex area and must be considered.  Practitioners with a good understanding of human behaviour will ensure this aspect is taken into account and design the safety solution accordingly.  A simple example of this relates to the passage above and panic.  This ‘flight’ behaviour tends to occur when people have received the warning of fire too late, a simple design remedy for this is ensuring an adequate fire detection and warning system.  Similarly, if we acknowledge that occupants prefer to use exits they are familiar with (such as their normal ingress/egress route) these can be sized and protected accordingly.

If we understand occupant behaviour in fire, we can design our buildings accordingly and ensure adequate life safety is achieved.

If you would like to know more – or would like to arrange an appointment with one of our senior fire safety advisers – simply call Peter Gyere on 020 8668 8663.

 

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