CIBSE Journal March 2010

Fire safety Sprinkler systems
0.45
0.60
30 minutes fi re resistance
0.4 30 minutes fi re resistance
0.55
60 minutes fi re resistance
60 minutes fi re resistance
0.50
0.35
90 minutes fi re resistance
90 minutes fi re resistance
0.45
0.3
0.40
0.25
0.35
F
requency
F
requency
0.30
0.2
0.25
0.15
Relative Relative
0.20
0.1
0.15
0.10
0.05
0.05
0
0
0 200 400 600 800 1000 1200 1400 1600 1800 2000 0 500 1000 1500 2000 2500 3000 3500 4000
Floor Area m
2
Floor Area m
2
Figure 4: Schools – relative frequency of Figure 5: Assembly and recreation – relative frequency
compartmentation failure of compartmentation failure
0.11 0.04
30 minutes fi re resistance
0.10
30 minutes fi re resistance
60 minutes fi re resistance
60 minutes fi re resistance
0.09
90 minutes fi re resistance
90 minutes fi re resistance
0.03
0.08
0.07
0.06
F
requency 0.02
F
requency 0.05
0.04
0.03
Relative 0.01
Relative
0.02
0.01
0 0
0 2500 5000 7500 10000 12500 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000
Floor Area m
2
Floor Area m
2
Figure 6: Manufacturing – relative frequency of
Figure 7: BB1000 – risk of compartmentation failure
compartmentation failure
versus compartment size
Updated guide
> In these examples, the iterative parametric fire beyond 140C, can be measured. The data in ﬁ gures
from CIBSE
calculation in Eurocode 1-1-2 and the heat transfer 4, 5 and 6 show the relative frequency that a real ﬁ re
calculations in Eurocode 3-1-2 were executed thousands will heat the unexposed surface of different sized,
A revised and updated of times using randomly selected values for ﬁ re load and ﬁ re resisting compartments in different buildings
CIBSE Guide E, on
ventilation. In the absence of statistical data, ventilation beyond 140C. A relative frequency of 1.0 means the
fi re engineering, is
values have been assumed to increase linearly between compartment enclosure always fails. The break in the
available soon. Written
by experienced fi re
the validated minimum and maximum opening values plots relates to the reduced risk of ﬂ ashover when
engineers, it offers permitted in EC1. The simulation process is illustrated sprinklers are introduced.
useful, practical advice
in ﬁ gure 3. As the ﬂ oor area of the ﬁ re compartment increases,
on fi re-safety engineering
and covers the latest
so will the frequency of ﬁ re starting. If this is factored
techniques. The new Compartments into the analysis, the results given in ﬁ gures 7, 8 and
edition includes details
Fire-separating elements are considered to have 9 are derived.
on BS9999 and other
sufﬁ cient ﬁ re resistance if, when subject to a controlled The graphs show that, for a school, the likelihood
recent developments. It
also has two completely
heating exposure [standard ﬁ re test], the temperature of a ﬁ re spreading from 800 sq m ﬁ re compartments,
new chapters on of the unexposed surface remains below an average without sprinklers – but with a 60 or 90-minute ﬁ re
performance-based
temperature of 140C [peak temperature of 180C]. This -resistant enclosure, is the same as that for a 12,000
design principles and
the application of risk
laboratory type test is run for different time periods (30, sq m compartment with sprinklers. It is noted that
assessment to fi re- 60, 90 and 120 minutes) depending upon the purpose the design guide, Building Bulletin 100: designing and
engineering designs. The
of the ﬁ re-separating element and nature and size of managing against the risk of fire in schools, calls for
new edition of Guide E
is due to be published in
the building in which it is to be placed. compartments with sprinklers to be no greater than
May. Call 020 8772 3618
Using the process outlined in ﬁ gure 3, the frequency 2,000 sq m.
or visit www.cibse.org/
that a real ﬁ re (typical of that which may occur in the Using the same approach, a 20,000 sq m
bookshop for more.
building) will heat the same ﬁ re-separating elements compartment can be achieved in assembly and >
52 CIBSE Journal March 2010 www.cibsejournal.com
CIBSEMar10 pp50-51,52,54 feature_fire.indd 52 2/25/10 5:39:09 PM
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