Finish your coffee or get out? The science behind evacuation
Most of us have experienced a fire alarm, whether it’s a drill or the real thing.
But how do we react, and what can fire safety professionals learn from human behaviour during evacuations?
A recent study looked at forty unannounced building evacuations across nightclubs, cinemas and restaurants to see precisely what happens between realising something is wrong and making for the exit.
Deviating from normality
The study looked at two models:
The behavioural model: used to describe human behaviour during a real evacuation
The engineering model: relates to the behavioural model but considers elements such as movement problems and the way they impact subsequent behaviour
The main difference between the two models is how the response to evacuation is interpreted. In the behavioural model, a movement towards an exit is a response, whereas, in the engineering model, it’s treated as a separate phase of the evacuation process.
The key events of an evacuation are well-defined. For instance, the first stage of interest is when the occupants realise something is wrong. This ‘deviation from normality’ is triggered by the alarm itself, a strange smell or unusual noise.
The next important event is when the occupants link the unusual situation to a hazard. It’s at this point when people decide to do something which reduces the consequences for either themselves or other occupants.
The 4-stage reaction to fire
The human response to fire consists of four stages:
- Receiving information. This relates to a cue, such as the sound of a fire alarm.
- Interpret. The stage at which we link the sound (be it a siren or voice) to a hazardous event. This is where people will either ignore or investigate the cues.
- Prepare. The reaction stage; acting on the given information, people will instruct others, investigate the cue or observe how others respond.
- Act. The response to the cue. This might be an evacuation, warning others, waiting or fighting the fire.
Building evacuations rarely follow a prescribed sequence or set of procedures; it’s a far more dynamic process which depends on the type of building and its occupants.
In the event of a fire alarm, the pattern above may take place in a different order or even be repeated during the evacuation.
The human element
There are lots of factors that influence how people respond to fire alarms and the path they take through the four-stage process above.
For instance, the study revealed that social influence and group behaviour plays a vital role during the early stages of evacuation. This might be because people don’t want to act alone or are influenced by crowding, which can prevent them from acting before others have done so.
Evacuation decisions are also influenced by our desire to find friends and family before exiting. This relates to the theory of affiliation, where people tend to seek something familiar during an emergency.
This is something we can all relate to; we usually feel safer in a known environment. It’s why we’re more likely to leave in groups or choose a known evacuation route such as the office entrance, even if an emergency exit is closer.
The study also discusses the role-rule model, where the way in which people react to emergencies is affected by an implied set of rules relating to their role. For instance, staff and customers in a shopping centre will probably have different reactions to an evacuation.
Which alarms are the most effective?
There are many different types of fire alarm on the market, but which is most effective?
Studies have revealed that voice alarms are the most effective for public buildings, but note that previous knowledge of the meaning and existence of an alarm will impact the evacuation response.
This might be why a simple alarm bell initiates an evacuation in an office environment faster than a shopping centre; office workers are more likely to be aware of the alarm sound and its meaning.
“But, I haven’t finished my coffee…”
Video recordings formed part of the research and revealed that in some instances, people would go back and forth between the recognition of a fire alarm and their response.
Restaurants and cafes demonstrated particularly long response times, not least because people seemed unwilling to leave the food or drink for which they’d paid.
It was a similar story in university lecture rooms where students would continue working before showing any recognition of the fire alarm. Likewise, office workers appeared to ignore the alarm initially to finish the task on which they were working.
Social influence plays a significant role in the recognition and response time. People observe others, and if their reactions don’t match what is believed to be the ‘right’ response to an alarm, they’ll react in the same way.
This was evident in the university and cinema experiments where occupants began evacuating only to stop and return to their seats when they realised others hadn’t moved.
The report is fascinating, but it’s clear that human behaviour during a fire rarely follows a predefined pattern – even if studies show there are common behavioural sequences.
It’s hoped that the information provided in the paper will be used to help fire safety professionals accurately predict the time required to evacuate different premises.