Introduction to Fire Safety Management
Introduction to Fire Safety Management
Introduction to Fire Safety Management
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<strong>Introduction</strong> <strong>to</strong> <strong>Fire</strong> <strong>Safety</strong> <strong>Management</strong><br />
fl oor of origin, vertical evacuation may still be necessary<br />
if the fi re is not brought under control.<br />
The advantage of Stage 3 travel is that those<br />
escaping should by this stage have reached a position<br />
where they are protected from fi re for a period of 30<br />
minutes or more. They should not encounter further fi re<br />
hazards en route <strong>to</strong> ultimate safety.<br />
For most of the occupants vertical evacuation will be<br />
by staircases. Normal accommodation access lifts should<br />
never be used in a fi re situation as the occupants may<br />
become trapped or be taken <strong>to</strong> a fl oor that is at risk from<br />
the fi re itself.<br />
For disabled people it may only be possible <strong>to</strong><br />
evacuate using a specially designed lift on an independent<br />
electrical supply, with the potential for fi re warden<br />
control and communications between the lift car and the<br />
evacuation control point.<br />
Stage 4 Travel – fi nal escape at ground level<br />
Stage 4 travel is from the foot of the staircase <strong>to</strong> the outside.<br />
The stairs should not all converge in<strong>to</strong> one common<br />
area at ground level, otherwise a single incident<br />
can block all escape routes.<br />
The fi nal exit and external design of a building<br />
also have <strong>to</strong> be considered in escape planning. It must<br />
be possible <strong>to</strong> leave the building and <strong>to</strong> get <strong>to</strong> a safe<br />
distance. The volume of people that may escape from<br />
a building governs their need for a readily identifi able<br />
assembly point or transfer area. Where large numbers of<br />
people may be involved, it will be necessary <strong>to</strong> plan these<br />
areas, so that access for the emergency services is not<br />
compromised.<br />
9.5.4 Escape exits<br />
Many assessments of rate of fl ow of persons through<br />
exits have been made following tests and simulation,<br />
particularly those using Paris fi remen in 1938 and 1945<br />
and on the London underground system.<br />
The generally accepted rate is 40 persons per<br />
minute per unit (0.75 m) exit width. This is an average<br />
fi gure and the actual fi gures varied between 20 and 170.<br />
Exit widths – the width of one unit corresponded<br />
<strong>to</strong> the average shoulder width and was determined<br />
<strong>to</strong> be 525 mm. Two units of 525 (i.e. 1050 mm) was<br />
the requirement for two people <strong>to</strong> travel through,<br />
shoulder-<strong>to</strong>-shoulder.<br />
However, there will be overlapping between groups<br />
of people and so further units of width required need<br />
only be an additional 450 mm.<br />
Hence, three units of exit width 525 525 450 <br />
1500 mm and four units would be 525 525 450 <br />
450 1950 mm.<br />
200<br />
Calculating exit capacity<br />
Where two or more exits are provided from either a<br />
s<strong>to</strong>rey exit or on ground fl oor, it should be assumed that<br />
one of the exits may be compromised by fi re thus preventing<br />
the occupants from using it. It is therefore essential<br />
that the remaining exit or exits are of suffi cient width<br />
<strong>to</strong> allow all persons <strong>to</strong> escape in the available time.<br />
Therefore when considering the adequacy of the<br />
means of escape for a building it is necessary always <strong>to</strong><br />
discount the largest available exit in any given situation.<br />
For example, if a social club room is expected<br />
<strong>to</strong> accommodate 150 people it will need <strong>to</strong> have two<br />
separate exits of a minimum width of 1050 mm each, or<br />
three exits of 850 mm each. It can be seen in this example<br />
that the capacity of the exits after one of the largest exits<br />
has been discounted is still suffi cient <strong>to</strong> comply with the<br />
guidance in the ADB regarding exit widths.<br />
Alternative escape routes – the 45º rule<br />
When considering the adequacy of the exit capacity it is<br />
also necessary <strong>to</strong> understand the term ‘separate exits’.<br />
Exits can only be regarded as separate if, from any point<br />
in the room or space in question, they are at least 45º<br />
apart.<br />
A<br />
45 or<br />
more<br />
C<br />
Figure 9.34 The 45º rule applied in rectangular space<br />
Alternative escape routes need <strong>to</strong> be sited <strong>to</strong> minimise<br />
the possibility of all of them being unavailable at the same<br />
time. Alternative escape routes should be either:<br />
(a) 45º or more apart (see Options 1 and 2 below) or<br />
(b) If less than 45º apart, separated from each other by<br />
fi re resisting construction.<br />
Option 1 – alternative routes are available from C<br />
because angle ACB is 45º or more, and therefore CA or<br />
CB (whichever is the less) should be no more than the<br />
maximum distance for travel given for alternative routes.<br />
Alternative routes are not available from D because<br />
angle ADB is less than 45º. There is also no alternative<br />
route from E.<br />
B<br />
less than 45<br />
E<br />
D