Civil Engineering Reference
In-Depth Information
the time between the fi re starting and people beginning
to evacuate was considerably longer than 30 seconds.
The enquiries suggest that early and informative warning
of the public is an absolutely critical aspect of any build-
ing evacuation management system. When dealing with
the evacuation of large numbers of the public it is also
vital that there is effi cient communications between
staff.
they can be motivated to make attempts to minimise the
impact of the fi re. There are numerous examples where
there have been signifi cant delays in raising the alarm
and/or calling the fi re service because an individual has
accidentally or negligently started the fi re for which he
knows he may well be sued or prosecuted.
Fire effl uent and/or heat
People may be exposed to one or all of the following
three main categories of fi re dynamics: fl ames, smoke
and heat. In a major fi re disaster any one or combination
of these exposures affects people's ability to react effect-
ively to the situation.
Flames
- exposure can be minimal, i.e. seeing the
fi re. Greater exposure will cause burns and can be life
threatening.
Smoke
- there is a strong relationship between
visibility and disinclination to move through smoke. The
general indication is that visibility has to be reduced
before people begin to be strongly deterred.
The majority of people become less inclined to
move through smoke when it is described by them as
'thick' or 'black'. This has been estimated to be when
visibility through smoke has been reduced to a minimum
of approximately 0-5 m.
Case studies of fi res have further shown that the
fl oor a person is located on and the thickness of smoke
conditions have a major infl uence on the likelihood of
a person using a room as a refuge and waiting for fi re
brigade rescue.
Heat
- there are fi re emergencies when people will
become aware of an increase in temperature. Exposure
to heat is most likely for those who are in the vicinity of
the origin of the fi re. Heat is a physiological stressor and
can be life threatening.
It is important to include the likely effects of
exposures to fi re effl uent and heat in both minor and major
fi re emergencies when devising evacuation procedures.
Stakeholding
The time that individuals take to respond to a fi re situ-
ation, the pre-movement behaviour and the time taken
to travel can be seriously affected by any stake that the
person may feel they have in the outcome of a fi re. For
example:
Financial stake
- if a person is liable to losses of
money as a result of a fi re they are likely to be motivated
to attempt to either fi ght the fi re or salvage valuable
assets. Enquiries into fi res indicate that having even a
relatively small fi nancial stake in the outcome of a fi re
has led people to lose their lives. There is an example
where the evacuation of a restaurant was delayed
because the customers had paid for their meal and were
determined to eat it rather than respond immediately to
a fi re alarm.
Moral stake
- if it is apparent that there may be loss
of life at a fi re, individuals will be motivated to attempt to
save people who are endangered. It is not only human
life that people are willing to delay their own evacu-
ation for, attempts to save animals, particularly family
pets, often result in people risking their lives rather than
getting to a place of safety.
Legal stake
- if a person feels that they may be
liable to be subjected to legal action as a result of a fi re,
Building design features
The building design will determine the travel distances
to reach a place of safety and therefore evacuation time.
The key characteristics of a building that impact upon
people's ability to evacuate in time of an emergency are:
➤
Use of the building
➤
Dimensions of the building, including the number of
fl oors
➤
Layout of the building, for example individuals' pre-
movement times are less variable in an open plan
setting such as offi ces, theatres, etc., than in other
settings
➤
Building services - including method of detection,
provision of warnings and fi re safety management
systems
Figure 10.10
Having a fi nancial stake in the outcome
can affect people's reaction to a fi re
