Civil Engineering Reference
In-Depth Information
total uncontrolled evacuation. Typically the sequence of
events for two-staged evacuation is as follows.
a place of ultimate safety. For example, when evacuat-
ing hospital patients from surgical theatres, they will be
initially moved to an adjacent fi re compartment within
the building prior to an eventual removal, if necessary.
Zoned evacuation
- a 'zoned' evacuation is
achieved by moving the occupants away from the fi re
affected zone to an adjacent zone. An example of this
would be a shopping centre where the occupants would
be moved to the adjacent smoke control zone while the
fi re affected zone was brought under control.
1.
An exclusive alert is given to staff (this may be
coded or a discreet visual or audible signal or
message)
2.
The situation is then investigated and the presence
of a fi re verifi ed (this is a limited period, and, if veri-
fi cation cannot be confi rmed in the prescribed time,
full evacuation will commence)
3.
The evacuation signal is then broadcast and
simultaneous evacuation commenced if:
9.5.2 Occupancy
➤
A fi re is confi rmed or
➤
The agreed investigation and verifi cation period
lapses without the alarm being cancelled or
One of the most signifi cant factors that infl uence the
design standards of the means of escape in any type of
building regardless of the method of evacuation adopted
is the nature, distribution and mental and physical state
of the occupiers. Approved Document B provides guid-
ance on appropriate aspects of means of escape based
on purpose groups.
These purpose groups take into account the types
and density of the occupants that should normally be
planned for in various buildings.
➤
Confi rmation of a fi re is received from more
than one source.
Total phased evacuation
- phased evacuation is a
common approach that is adopted in high-rise premises,
where the fl oors are separated by fi re resistant construc-
tion. It may also be adopted in a similar way to the pro-
gressive evacuation for hospitals and residential care
homes (see below). In these cases simultaneous evacu-
ation would be impractical due to the numbers of people
involved, the travel distances and the limited numbers of
stairs and exits.
In a phased evacuation it is common that the fi rst
people to be evacuated are all those on the storeys
immediately affected by the fi re, usually the fi re fl oor and
the fl oor above; the remaining fl oors are then evacuated,
two fl oors at a time, at phased intervals.
In order to safely adopt a phased approach it is
necessary to provide and maintain additional fi re protec-
tion measures and supporting management arrange-
ments. It is often the case that those with physical
impairments, either temporary or permanent, are moved
to a place of relative safety as part of the personal
emergency escape plan (PEEP) (see Chapter 10).
In schools the occupants are assumed to be
awake, in the main young and able bodied,
subject to discipline and very familiar with
the building they may need to escape from.
Whereas in a hotel, the occupants are often
asleep, not disciplined, potentially under the
infl uence of alcohol and not familiar with the
building that they may need to escape from.
For this reason the physical condition, state
of consciousness and their expected reac-
tions must be considered at the design stage
of any building. Moreover, the means of
escape should be reviewed at the time when
any alterations are made to a building.
Progressive evacuation strategy
As an alternative to total evacuation, it is sometimes
necessary to consider a progressive evacuation strategy.
Progressive evacuation is typically adopted in hospitals
where fi re-resisting compartments are provided to allow
the evacuation of non-ambulant patients on a phased
basis whereby they are moved into adjoining compart-
ments prior to assisted removal from the building.
There are two types of progressive evacuation
procedures that can be adopted:
Progressive horizontal evacuation
- progres-
sive horizontal evacuation is the process of evacuating
people into an adjoining fi re-resisting compartment on
the same level, from which they can later evacuate to
Appendix 9.1 summarises the purpose groups that are
used in ADB. It can be seen that the categorisation into
purpose groups takes account of the physical condi-
tion, state of conciseness and expected reactions of
the occupancy of a building. However, occupancies
vary throughout the life of a building and it is important
that these factors are considered when developing and
managing evacuation procedures once the building is
occupied.
When considering the occupancy of a building
and how it may impact upon the requirements for the
