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Frank et al. Fire Science Reviews 2013, 2:6
http://www.firesciencereviews.com/content/2/1/6
REVIEW Open Access
A review of sprinkler system effectiveness
studies
Kevin Frank1*, Neil Gravestock2, Michael Spearpoint1and Charles Fleischmann1
Abstract
A lack of information on the effectiveness of fire safety systems, including sprinklers, has been noted as being a
limiting factor in the development of performance-based fire safety design. Of the fire safety systems available,
sprinkler operation has been studied most extensively. This paper reviews the information currently available on
sprinkler effectiveness in fires. Two approaches are generally taken for estimating sprinkler effectiveness:
component-based approaches using a fault tree or similar method and system-based approaches using fire incident
data where sprinklers were present. In this paper, sprinkler system component data and effectiveness estimates from
system-based studies have been compiled and tabulated, with a comparison of the merits of the two approaches.
Recommendations for using the data for design purposes are made, including considerations for uncertainty and
using a hybrid system/component approach for specific sprinkler system comparisons. These recommendations
provide input on the reliability of systems in the development of performance-based fire safety design methods.
Keywords: Sprinklers; Effectiveness; Reliability; Suppression
Introduction
Building fire safety design involves evaluation of the like-
lihood and consequences or risk of potential fire events
that may impact the fire safety objectives of the building.
Objectives are set by regulation and/or by the owner
and/or user and/or insurer of the building. These objec-
tives universally include an adequate (but usually unquan-
tified) level of safety for the occupants of the building,
some facilitation of firefighting should a fire occur in the
building, and some limitation of the physical damage that
would result from a fire in the building.
Systems are commonly installed in buildings to pro-
vide a cost-effective mitigation of the risk to life safety
and/or property destruction, etc. The contribution and
interactions of each of the systems towards achieving the
objectives should be known. This either requires histori-
cal data that directly addresses effectiveness or historical
data on the reliability of the system (the probability that
the system will operate as required at any time) and on the
effect of the correctly operating system (the efficacy) on
each of the objectives that it is intended to address. Some
*Correspondence: kfrank81@gmail.com
1University of Canterbury, Christchurch, New Zealand
Full list of author information is available at the end of the article
systems, while positive in relation to some objectives, may
be negative in relation to other objectives.
In the move towards risk- and performance-based fire
safety design (Notarianni and Fischbeck 1999) identi-
fied “7 major barriers to determining and documenting
achievement of agreed upon levels of fire safety”,one
of which was that “no standardized methods exist to
incorporate reliability of systems.” At an October 2006
meeting in Wellington, New Zealand, the International
Forum of Fire Research Directors which includes mem-
bers from the Building Research Association of New
Zealand (BRANZ), the Commonwealth Scientific and
Industrial Research Organisation (CSIRO), the National
Institute of Standards and Technology (NIST), FM Global,
the National Research Council of Canada (NRCC), and
the Society of Fire Protection Engineers (SFPE) among
others, listed as 2 of their top 5 research priorities
(Grosshandler 2006):
•
“to improve our ability to predict the impact of
active fire protection systems on the fire growth
and fate of combustion products; and
•
to estimate the various contributions to
uncertainty and to incorporate them into hazard
and risk analyses”
©2013 Frank et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction
in any medium, provided the original work is properly cited.
Frank et al. Fire Science Reviews 2013, 2:6 Page 2 of 19
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for developing the next generation of performance-based
fire safety design tools (Croce et al. 2008). (Beyler 1999)
stated that “the reliability of fire suppression systems
remain[s] a subject of great uncertainty due to our unwill-
ingness or inability to assess reliability from historical
data.” A New Zealand example where the inability to
quantify fire safety system effectiveness was a substantial
barrier to evaluating alternative fire designs occured in
the single means of escape determinations in 2005-2006,
where it was noted that “there is as yet inadequate data
for fire engineering to achieve the accuracy that is expected
from, for example, structural engineering... In particular,
the probabilities used for a fire analysis must be based
on fire statistics derived from a comparatively small data
pool... that applies not only to fire scenarios but also to
the proper functioning of critical systems including the
sprinklers” (Department of Building and Housing 2005).
Automatic fire sprinkler systems are designed to acti-
vate if a fire develops in their area of protection and limit
or suppress the further development of the fire. Thus,
when evaluating a building design that incorporates sprin-
klers for fire safety, knowledge of the effectiveness of
sprinkler systems in reducing the risk from fire is impor-
tant. Similarly the development of codified approaches
to the design of systems (e.g. sprinkler standards) bene-
fit from the knowledge of the effectiveness of the systems
currently in use.
Different methods of analysing risk to fire safety in
buildings have been developed. One method that has been
described in fire safety engineering guidelines (British
Standards Institution 2003) and used in fire risk anal-
ysis case studies in Australia (Thomas et al. 1992) and
New Zealand (Enright 2003) (among others) is to dis-
cretise expected fire outcomes using an event tree. A
typicaleventtreecanbeseeninFigure1.Branchesonthe
event tree represent mutually exclusive outcomes from
individual events, with the probability of each event out-
come being represented by a value or distribution. Where
sprinklers are included in the design, the probability of
successful sprinkler operation can be included as an event.
Specialised software has also been developed for evalu-
ating fire risk. Probability estimates of sprinkler effective-
ness and/or reliability may be required in a similar manner
to the event tree approach (Yung and Benichou 2000).
One difficulty with using the approaches discussed
above is determining the values that should be used for
the probability of the events, such as the event that the
sprinkler system operates successfully. Additionally, it can
be difficult to determine how a value should be adjusted if
the system is modified, which is particularly important in
comparative risk assessment. An example involving sprin-
klers that has been encountered in New Zealand was how
the probability of successful sprinkler operation should
be adjusted if a single towns’ main water supply was
supplemented with a secondary tank supply (Department
of Building and Housing 2005).
In fire and smoke spread models (such as zone and field
models) used for fire safety analysis, sprinklers are gen-
erally assumed to have an effect on the heat release rate
of the fire. A common assumption for the performance of
a sprinkler system in a performance-based design is that
the heat release rate of the fire will not exceed the heat
releaserateatthetimeofsprinkleractivation,asshown
in Figure 2, typically described as controlling the fire. This
approach is described in the International Fire Engineer-
ing Guidelines (Donaldson et al. 2005), and is also rec-
ommended in other performance-based approaches such
as the New Zealand Verification Method (Department of
Building and Housing 2012). As it is difficult to quantify
sprinkler performance in real fires in terms of heat release
rate, a number of other criteria have been used, such as:
•fire containment to room of origin
•number of sprinklers activated
•amount of damage to structure and property
•required amount of fire service intervention
•occupant injuries or fatalities
The differences in these criteria make it difficult to
apply the reported sprinkler effectiveness probabilities
to fire risk modelling. The use of these criteria in the
studies identified in the literature is discussed in Section
“System-based studies”.
Sprinkler performance in fires may depend on the fol-
lowing factors:
•sprinkler and sprinkler system characteristics
•age and deterioration
•inspection, testing, and maintenance
•standards and technology available at the time of
design
•modifications
•changes in building use or hazard being protected
•building design
•other building systems, such as heating and
ventilation
•water supply changes
among others. A number of studies have been published
which provide information on sprinkler system effective-
ness. Since automatic sprinkler systems were originally
invented and developed in the 1800s (Grant 1996), there
has been debate as to how effective they are. An early ref-
erence to estimates of sprinkler effectiveness can be found
in the Preliminary Report of the New York State Factory
Investigating Commission, which was released in 1912 fol-
lowing the Triangle Shirtwaist fire. This report stated that
(New York State Factory Investigating Commission 1912):
Frank et al. Fire Science Reviews 2013, 2:6 Page 3 of 19
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Figure 1 Typical event tree for 3 events, with event probabilities P1-P
3.Successful sprinkler fire control is represented as the second event.
“Testimony as to the efficacy of sprinkler systems varies,
but the lowest estimate of their proper working is 75 per
cent and the highest 95 per cent.”
It is unknown what information this testimony was
based on. As the 20th century progressed, several other
organisations recorded information on the operation of
sprinklersystems.Someofthesestudieshavebeenused
by the examples of risk-informed fire safety engineering
previously discussed in this paper. This paper reviews the
information currently available from studies on sprinkler
system effectiveness in the context of using this informa-
tion for building fire safety design. This review does not
generally attempt to judge the value of existing studies as
Heat release rate
Time
Sprinkler
Operation
Effective
control
Figure 2 A commonly assumed heat release rate curve for
sprinkler fire control.
that judgement will depend on the context of the approach
to obtain the data and the data application.
Definitions
There are several different terms used to describe the
successful operation of fire safety systems. For the pur-
poses of this study, “reliability” is defined as the probability
that a sprinkler system will activate and supply water to a
fire demand. “Efficacy” is defined as the probability that
the sprinkler system will affect the development of the
fire as specified in the system design objectives, given
that it operates. “Effectiveness” is a term describing the
overall performance of the sprinkler system, combining
both the reliability and efficacy. These definitions have
been used in other studies on sprinkler systems, such
as those by (Thomas 2002). “Availability” describes the
probability that the system will not be out of service for
inspection, testing, or maintenance, and is included in
reliability.
This review does not consider the potential for sprinkler
systems to fail when there is no fire present. Such situa-
tions may include rupture due to freezing or mechanical
damage leading to water damage, or activation in non-fire
conditions. These types of failure are not generally directly
considered in a building fire risk analysis, but they may be
relevant for other purposes, such as a cost/benefit analysis
for installing specific fire protection systems.
Sprinkler system reliability and effectiveness as defined
do not directly translate to impact measures; for example,
reduction of property damage or a reduction of fatalities.
They are a measure of the ability of the sprinkler system
Frank et al. Fire Science Reviews 2013, 2:6 Page 4 of 19
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to respond and to meet the design objectives, respectively.
As an extreme example, a “100% effective” sprinkler sys-
tem would not equate to a 100% reduction in loss, because
afiremustbepresentandreachsufficientsizetoactivate
the sprinkler system as designed and thus there will always
be a measure of loss in a sprinklered fire. Impact measures
arediscussedlaterinthispaper.
Types of sprinkler effectiveness studies
Two general approaches have been used in previous stud-
ies taken to quantify sprinkler effectiveness:
1. Component-based (fault tree)
2. System-based (incident data)
The component-based approach builds an effective-
ness estimate for a system from individual component
data. The system-based approach estimates the effec-
tiveness of the entire system directly from past per-
formance in actual fire incidents. For design purposes,
either approach have been used with data obtained from
already installed systems or “expert judgement” esti-
mates if data was deemed to be lacking or insufficient.
Expert judgement is not defined in this paper although
such estimates are subject to an expertŠs level of exper-
tise and personal biases. This review will compare the
effectiveness estimates obtained from component-based
approaches and system-based separately, and subse-
quently attempt to reconcile them to compare differences
and similarities between the values obtained through each
approach.
Other sprinkler effectiveness review studies
Sprinkler effectiveness reviews have been conducted
by (Bukowski et al. 1999; Feeney 2001; Koffel 2005;
Richardson 1985; Smith 1983), and (Sakenaite 2009).
Several studies combine a review of other sources and
new data, including (Budnick 2001; Finucane and Pinkney
1988), and (Gravestock 2008).
Component-based studies
Component-based studies of sprinkler performance use
estimates of individual component and model a combi-
nation of them using some approach, typically a fault
tree, to obtain an estimate of the system reliability. These
studies typically provide a reliability estimate for the sys-
tem only since it is difficult to attribute system efficacy
to individual components. A notable exception was com-
pleted by (Gravestock 2008), who combined estimates of
sprinkler efficacy in smouldering, flaming non-flashover,
and flashover fires with a reliability fault tree to estimate
an overall effectiveness.
Component-based reliability data is either reported as
a failure probability per demand or a failure rate for a
unit time. The following formula is used to calculate per
demand probability from a failure rate:
P(per demand)=1−e−λt(1)
where λisthefailurerateandtisthetimebetween
maintenance, inspection, or replacement. This equation
is found in various sources (for example, (Lees 2005))
and can be used to convert the following component data
from failure rate to failure probability per demand, but
it assumes the failure rate is constant over time and will
depend on the time period used so it is specific to each
application. Thus, the data here is included with the same
units and type as originally reported in the literature. Care
must be exercised comparing seemingly equivalent data as
different methods will have been used to obtain the data
and/or different criteria nominated to designate failure.
Component-based reliability probabilities can be com-
bined to estimate system reliability through fault trees. A
simple fault tree is shown in Figure 3. Individual compo-
nent reliability probabilities can be combined, or if data on
unique failure modes for individual components is known
then they can be included as well. Note that the equations
shown for the AND and OR logic assume that the relia-
bility probabilities are independent, which may not always
be a realistic assumption if there are significant common-
cause failure modes. The fault tree used for a specific
sprinkler system will depend on the components that are
present in the system.
Sprinkler system component data
Table 1 shows the identified studies that provide sprinkler
system component data. Component data has been clas-
sified as related to sprinkler head operation (Table 2),
sprinkler piping (Table 3), valves (Table 4), pumps
(Table 5), water supplies (Table 6), and miscellaneous
components (Table 7).
(Moelling et al. 1980) evaluated sprinkler systems in four
nuclear power plants using a fault tree approach. Failure
was considered to be system failure to operate on demand,
and the performance of the sprinkler system after oper-
ation was not considered. While specific information for
each of the sprinkler systems was not presented, proba-
bilities for 8 failure modes were included. The source of
the probabilities used was not made explicit. Two of these
were human-based: inadvertently closed valves and failing
to trip a manual release. System reliability was found to be
most sensitive to the probability of an inadvertently closed
valveandthetimebetweeninspections.
(Finucane and Pinkney 1988) and (Nash and Young
1991) provided similar failure rates for multiple sprinkler
system components, apparently both sourced from 1972
UK Atomic Energy Authority data.
Budnick (Budnick 2001; Hughes Associates, Incorpo-
rated 1998) collected inspection, test, and maintenance
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Figure 3 A basic example of a fault tree. The equations shown assume the probabilities are independent. For the sprinkler system application,
included components could be water supplies, sprinkler heads, piping, valves, or other components. Additional components and sub-component
levels can be added as required.
Table 1 Studies providing data on sprinkler system component reliability
Source Country Source of data Application focus
(Watanabe 1979) Japan Maintenance records Japanese buildings
(Moelling et al. 1980) US Unknown US nuclear installations
(Finucane and Pinkney 1988) UK UKAEA Systems Reliability Service General
(Nash and Young 1991) UK UKAEA Systems Reliability Service General
(Budnick 2001) US Collected from several sprinkler systems General
in one complex over 66 months
(Ronty and Keski-Rahkonen 2004) Finland Finnish nuclear plant Buildings in Finland
electronic maintenance reports, (emphasis on nuclear)
non-nuclear building inspectionn statistics (emphasis on nuclear)
(Hauptmanns et al. 2008) Germany OREDA, IAUT-AC report General
(Gravestock 2008) New Zealand New Zealand fire protection fire safety systems
industry surveys fire safety systems
(Moinuddin et al. 2009) Australia Historical data from 23 Australian * Australian high-rise
high-rise office buildings aged 4 to 36 years* office buildings
(SINTEF 2009) Offshore oil and gas installation Oil and gas
(10 - 43 pieces of equipment from 1 - 9 installations) installations
(Brammer 2010) Australia and water supplies
New Zealand
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Table 2 Data on sprinkler head reliability
Description Source Unit Minimum Mean Maximum
Removal (Watanabe 1979) per demand 3.0 ×10−6
Deformation (Watanabe 1979) per demand 4.61 ×10−4
Leakage (Watanabe 1979) per demand 3.36 ×10−4
Obstruction (heat and water) (Watanabe 1979) per demand 1.467 ×10−3
Partition rearrangement (Watanabe 1979) per demand 4.89 ×10−4
Paint loading (Watanabe 1979) per demand 6.5 ×10−5
Failure (Moinuddin et al. 2009) per demand 7.82 ×10−2
Fire detectors fail to function (Moelling et al. 1980) per demand 1.99 ×10−32.97 ×10−34.45 ×10−3
Fail to open (Moelling et al. 1980) per demand 1.00 ×10−6
Failure (Ronty and Keski-Rahkonen 2004) failures/year 1.50 ×10−41.70 ×10−41.80 ×10−4
Sprinkler installation (Ronty and Keski-Rahkonen 2004) failures/year 8.0 ×10−31.1 ×10−21.4 ×10−2
New (fail dangerous) (Nash and Young 1991) failures/year 3.10 ×10−2
Old (fail dangerous) (Nash and Young 1991) failures/year 5.10 ×10−2
Failure to flow water (Finucane and Pinkney 1988) failures/year 2.0 ×10−2
Water released but (Finucane and Pinkney 1988) failures/year 8.0 ×10−2
not in intended pattern
failure data on nine types of component from six sprinkler
systems in one facility.
(Hauptmanns et al. 2008) employed the most compre-
hensive fault tree of the reviewed studies with 60 possible
contributing events. Failure probabilities for each event
were assigned to a class ranging from 1 to 6 correspond-
ing to an order of magnitude failure probability from
0.1-0.8 to 0.00001-0.0001, respectively. For the specific
system considered in the analysis presented in Haupt-
mann’s paper, failure probabilities of 7.1×10−4,5.5×10−2,
6.4×10−5,and3.1×10−3were estimated for the sprin-
kler piping network, alarm valve station, water supply, and
pumps, respectively.
(Ronty and Keski-Rahkonen 2004) looked at main-
tenance records from sprinkler systems in Finland to
estimate sprinkler reliability. The focus of the study was
sprinkler systems in nuclear facilities but the authors
concluded that there was an insufficient amount of data
available from Finnish nuclear facilities so they also col-
lected data from non-nuclear facilities. The values listed in
this paper were obtained from the non-nuclear facilities,
and Ronty and Keski-Rahkonen note that this data should
be used with caution due to “insufficient critical analysis
of the data”.
(Watanabe 1979) estimated the failure rates of sprin-
kler subsystems and components from the maintenance
records of 97 sprinkler systems in Japan. These systems
included a total of 121,991 sprinkler heads and 707 piping
arrays. Overall sprinkler reliability, capability (efficacy),
availability, and effectiveness were estimated at 98.9%,
99.9%, 99.3%, and 98%, respectively.
(Moinuddin et al. 2009) surveyed sprinkler systems in
23 high-rise office buildings in Australia, out of a total
of 60 buildings whose staff was contacted for informa-
tion. Moinuddin observed that the buildings that did
not participate may have had a lower standard of main-
tenance than those that did. The data was used in a
fault-tree analysis to estimate sprinkler system reliability
for upfeed (water supplied from the base of the build-
ing) and downfeed (water supplied by gravity from above)
configurations.
Offshore Reliability Data (OREDA) is an organisation
that collects reliability data for the petroleum indus-
try. Data is collected on several components that may
be relevant to specific sprinkler systems, including del-
uge valves and pumps (SINTEF 2009). The focus of the
dataset is on offshore oil and gas installations which
may not be applicable to onshore building sprinkler
systems.
(Brammer 2010) conducted a study into the reliability
of secondary water supplies as required by the New
Zealand sprinkler standard NZS:4541 (2007) (Standards
Table 3 Data on sprinkler piping reliability
Description Source Unit Minimum Mean Maximum
Pipe array (Ronty and Keski-Rahkonen 2004) failures/year 2.4 ×10−63.3 ×10−64.3 ×10−6
Gasket failure (Budnick 2001) failures/hour 5.00 ×10−74.00 ×10−61.20 ×10−5
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Table 4 Data on sprinkler system valve reliability
Description Source Unit Minimum Mean Maximum
Sector control valve mishandled (Watanabe 1979) per demand 2.08 ×10−3
Priming tank gate valve (Watanabe 1979) per demand 2.47 ×10−3
Deluge fail to open (Moelling et al. 1980) per demand 8.9 ×10−41.9 ×10−33.6 ×10−3
Check fail to open (Moelling et al. 1980) per demand 3.0 ×10−51.0 ×10−43.0 ×10−4
Closed inadvertently (ICV) (Moelling et al. 1980) failures per hour 6.3 ×10−76.3 ×10−66.3 ×10−5
Alarm (Moinuddin et al. 2009) per demand 2.0 ×10−32.94 ×10−3
Main stop (Moinuddin et al. 2009) per demand 2.3 ×10−33.19 ×10−3
Zone isolation (Moinuddin et al. 2009) per demand 2.2 ×10−23.17 ×10−2
due to tenancy changes
Ordinary stop (Moinuddin et al. 2009) per demand 6.7 ×10−49.60 ×10−4
Non-return (Moinuddin et al. 2009) per demand 1.1 ×10−31.76 ×10−3
Pressure reducing (Moinuddin et al. 2009) per demand 4.77 ×10−31.04 ×10−2
Wet alarm (Nash and Young 1991) failures/year 4.0 ×10−5
Alternative alarm (Nash and Young 1991) failures/year 8.0 ×10−5
Main sprinkler stop (Nash and Young 1991) failures/year 2.0 ×10−4
Non-return (Nash and Young 1991) failures/year 1.0 ×10−2
Main stop (Finucane and Pinkney 1988) failures/year 2.3 ×10−3
Non-return (Finucane and Pinkney 1988) failures/year 1.0 ×10−2
Main sprinkler stop (Finucane and Pinkney 1988) failures/year 2.0 ×10−3
Wet alarm (Finucane and Pinkney 1988) failures/year 4.0 ×10−4
Alternative alarm (Finucane and Pinkney 1988) failures/year 8.0 ×10−4
Post indicating (Budnick 2001) failures/hour 0
Alarm check (Budnick 2001) failures/hour 0
Outside stem and yoke (Budnick 2001) failures/hour 7.5 ×10−83.6 ×10−78.7 ×10−7
Main drain (Budnick 2001) failures/hour 0
Inspector’s test (Budnick 2001) failures/hour 2.3 ×10−68.3 ×10−61.8 ×10−5
Alarm (Ronty and Keski-Rahkonen 2004) failures/year 6.5 ×10−41.2 ×10−32.0 ×10−3
Deluge (Critical) (SINTEF 2009) failures/ 2.8 5.8 9.4
106calendar hours
Deluge (All Modes) (SINTEF 2009) failures/ 12 21 31
106calendar hours
New Zealand 2007) in some circumstances. He also
provided reliability estimates for single sprinkler system
water supplies. A case study for the water supply system
for Adelaide, Australia was included.
Along with providing a review of other sources and
recommending fire safety system component reliability
distributions for risk assessment purposes, Gravestock
listed sprinkler system deficiency data from inspec-
tions in New Zealand, and also collected survey data
on 1,293 New Zealand sprinkler systems from 1999
to 2007, shown in Table 8 (Gravestock 2008). Of the
buildings included in the survey, 94% of office build-
ings, 76% of apartment buildings, and 89% of the total
building population had sprinkler systems with minor or
no defects found. The apartment buildings had a higher
proportion of unprotected areas, pump start defects, and
inadequate water supplies, although it should be noted
that there were only 42 sprinkler systems in apartment
buildings included in the survey so there is a large
amount of uncertainty due to the small population of
buildings. Multi-storey office and apartment buildings
accounted for approximately 10% and 3% of the sur-
vey results, respectively. The category “all building types”
included retail, crowd occupancy, healthcare, education,
and industrial buildings in addition to office and apart-
ment buildings.
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Table 5 Data on sprinkler system pump reliability
Description Source Unit Minimum Mean Maximum
Starting device (Watanabe 1979) per demand 6.84 ×10−3
Fail to start (Moelling et al. 1980) per demand 4.5 ×10−31.4 ×10−22.4 ×10−2
Diesel (Moinuddin et al. 2009) per demand 8.41 ×10−21.21 ×10−1
Electric (Moinuddin et al. 2009) per demand 1.27 ×10−21.90 ×10−2
Diesel (Ronty and Keski-Rahkonen 2004) failures/year 8.7 ×10−31.5 ×10−22.3 ×10−2
Electric (Ronty and Keski-Rahkonen 2004) failures/year 2.5 ×10−36.2 ×10−31.3 ×10−3
Diesel (Critical) (SINTEF 2009) failures/ 120 210 310
106calendar hours
Diesel (All Modes) (SINTEF 2009) failures/ 680 840 1000
106calendar hours
Electric (Critical) (SINTEF 2009) failures/ 24 72 170
106calendar hours
Electric (All Modes) (SINTEF 2009) failures/ 120 210 340
106calendar hours
Seismic damage to sprinkler system components
There has been some research conducted into the
integrity of sprinkler systems following earthquakes, such
as the Northridge event on January 17, 1994 in California
(Fleming 1998; Todd et al. 1994), the January 17, 1995
Kobe, Japan earthquake (Sekizawa et al. 2003), and the
Canterbury earthquakes in New Zealand in 2010 and
2011 (Houston and Mak 2010), although there has been
no data found on sprinkler performance in fires after
earthquakes. After the Northridge event, while broken
pipes and sheared off sprinklers were found in some
instances it was observed that many sprinkler systems
were not damaged, particularly in modern systems that
met the latest seismic codes and standards. It was esti-
mated that 41% of the sprinkler systems in Kobe city were
damaged after the Kobe earthquake. In the Canterbury
earthquakes, several tank water supply sources failed that
had been put in place to provide a source of water for
the sprinklers if the reticulated supply was compromised.
Based on these findings, research into improved design
methods for seismic resiliency of tank supplies is ongo-
ing and changes are proposed to the 2013 release of the
New Zealand automatic fire sprinkler standard from this
work.
System-based studies
Total system-based studies generally use data from sys-
tem operation in previous fire events from a popula-
tion of buildings to estimate measures of effectiveness.
The alternative approach is to obtain expert judgement
through surveys or Delphi methodology. The estimates of
sprinkler effectiveness from these studies are always on a
per demand basis since the data comes from actual system
demands.
Table 6 Data on sprinkler system water supply reliability
Description Source Unit Minimum Mean Maximum
Dual supplies (Brammer 2010) per demand 5.0 ×10−92.4 ×10−5
Town main (Brammer 2010) per demand 5.6 ×10−41.1 ×10−2
Pumped supply (diesel) (Brammer 2010) per demand 1.8 ×10−33.8 ×10−3
Elevated tank (Brammer 2010) per demand 1.9 ×10−41.8 ×10−3
Town main (Moinuddin et al. 2009) per demand 1.87 ×10−43.72 ×10−4
Gravity tank (Moinuddin et al. 2009) per demand 2.28 ×10−42.28 ×10−4
Storage tank (Moinuddin et al. 2009) per demand 4.64 ×10−39.34 ×10−3
Water supply line (per m) (Moinuddin et al. 2009) per demand 1.29 ×10−52.18 ×10−5
Town main (Ronty and Keski-Rahkonen 2004) failures/year 2.6 ×10−41.0 ×10−32.5 ×10−3
Storage tank (Ronty and Keski-Rahkonen 2004) failures/year 6.5 ×10−3
Pressure tank (Ronty and Keski-Rahkonen 2004) failures/year 1.0 ×10−32.0 ×10−29.3 ×10−2
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Table 7 Miscellaneous sprinkler system component data
Description Source Unit Minimum Mean Maximum
Pressure switch (Watanabe 1979) per demand 8.99 ×10−4
Down time (Watanabe 1979) per demand 3.7 ×10−3
Incomplete protection (Watanabe 1979) 1.03 ×10−4
Alarms fail to function (Moelling et al. 1980) per demand 2.68 ×10−23.62 ×10−24.81 ×10−2
Personnel fail to trip manual release (Moelling et al. 1980) per demand 2.00 ×10−1
Back-up batteries for diesel pump (Moinuddin et al. 2009) per demand 2.68 ×10−24.92 ×10−2
Mains power in building (Moinuddin et al. 2009) per demand 1.61 ×10−43.11 ×10−4
Building power generator (Moinuddin et al. 2009) per demand 5.24 ×10−31.25 ×10−2
Pressure switch (Moinuddin et al. 2009) per demand 7.82 ×10−31.17 ×10−2
Direct brigade alarm (Moinuddin et al. 2009) per demand 5.27 ×10−39.57 ×10−3
Jacking pump (Moinuddin et al. 2009) per demand 9.85 ×10−31.55 ×10−2
Back-up batteries for brigade alarm (Moinuddin et al. 2009) per demand 2.57 ×10−36.71 ×10−3
Alarm motor and gong (Nash and Young 1991) failures/year 1.6 ×10−2
Accelerator (Nash and Young 1991) failures/year 7.9 ×10−3
Alarm motor and gong (Finucane and Pinkney 1988) failures/year 1.6 ×10−2
Accelerator (Finucane and Pinkney 1988) failures/year 8.0 ×10−3
Flow alarm (Budnick 2001) failures/hour 5.80 ×10−61.50 ×10−52.70 ×10−5
Motor gong (Budnick 2001) failures/hour 4.10 ×10−52.50 ×10−51.30 ×10−5
Fire department connection (FDC) (Budnick 2001) failures/hour 0
A number of past system studies provide an estimate
of sprinkler system effectiveness from fire incident data,
shown in Table 9. The estimated effectiveness ranges from
a minimum of 70.1% to a maximum of 99.5%, which corre-
sponds to failure rates ranging from 60 failures in 200 fires
to 1 failure in 200 fires.
The NFPA has published information on sprin-
kler system effectiveness in the United States since
Table 8 New Zealand survey data on 1,293 sprinkler
systems from 1999 to 2007 (Gravestock 2008)
Fault/Issue Office Apartment All building types
Inadequate supply 1.97% 2.38% 1.70%
Signalling fault 1.32% 2.38% 1.08%
Fire service inlet 0.66% 0.00% 1.01%
Flow switch 0.00% 0.00% 0.23%
Floor isolation 0.00% 0.00% 0.08%
Street valve 3.95% 0.00% 0.62%
Pump performance 2.63% 0.00% 1.47%
Pump start 3.29% 4.76% 1.24%
Hydraulic gong 0.00% 0.00% 0.15%
Anti-Interference gear 2.63% 0.00% 0.85%
Isolated 0.66% 0.00% 0.23%
Pressure switch 0.00% 4.76% 0.15%
Unprotected areas 1.97% 9.52% 2.48%
1897. Estimates of satisfactory or unsatisfactory per-
formance of sprinklers in fires are available from
1897 to 1964. It was noted that this data set did
not include numerous fires extinguished by one
or two sprinklers. Information on the rationale for
unsatisfactory and satisfactory performance has
not been identified for the NFPA data from 1897
to 1925. The NFPA has noted that reporting cate-
gories related to sprinkler performance were modified
with the introduction of the National Fire Inci-
dent Reporting System (NFIRS) Version 5.0. This
change was intended to improve the estimates of
sprinkler reliability from the NFIRS data (Rohr and
Hall 2005).
(Knudsen and Bygbjerg 2009) presented data from
Danish sprinkler system inspection reports from 2001,
2007, and 2008. Deficiencies were placed into four
categories:
•Category A: significant defects/deficiencies that will
prevent the entire system from operating adequately
(must be fixed before approval),
•Category B: defects/deficiencies that will prevent a
portion of the system from operating adequately
(approval will lapse if not fixed in 2 months),
•Category C: minor defects/deficiencies (must be fixed
in 12 months or defect/deficiency is upgraded to
category B), and
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Table 9 System-based sprinkler effectiveness studies which provide a direct estimate of sprinkler system effectiveness
from past fires in sprinklered buildings
Data collected Building Number Nominal reported
Source Country from years population/location of events effectiveness
(Tryon and McKinnon 1969) US 1897-1924 United States 32778 95.8%
(Tryon and McKinnon 1969) US 1925-1964 United States 75290 96.2%
(Hall 2006) US 1999-2002 NFIRS 5.0 data Not Reported 89%
(Hall 2007) US 2002-2004 NFIRS 5.0 data Not Reported 90%
(Hall 2010) US 2003-2007 NFIRS 5.0 data 44310 91%
(Hall 2012) US 2006-2010 NFIRS 5.0 data 47520 88%
(US Department of Energy 2004) US 1955-2003 US DOE facilities 251 98.8%
(Miller 1974) US 1970-1972 FM insured properties 1355 85%
(Powers 1979) US 1969-1978 City of New York 5709 97.0%
(Taylor 1990) US 1982-1986 US general office buildings 6400 per year∗81.3%
(Linder 1993) US 1988-1993 Industrial Risk Insurers 3446 94.9%
(Baldwin and North 1971) UK 1967-1968 UK fire brigade data 619 94%
(Marryatt 1988) Aus/NZ 1886-1986 Australia/New Zealand 9022 99.5%
(Frank et al. 2012) NZ 2001-2010 New Zealand 1171 86%
(Juneja 2004) Canada 1995-2002 Ontario Fire Marshal data 2536 70.1%
∗Estimated.
•Category BC: multiple category B or C
defects/deficiencies that cumulatively are expected to
equate a category A defect/deficiency.
On average, Knudsen and Bygbjerg found that 2% of
inspected Danish sprinkler systems had sufficient prob-
lems to not be approved, while 40% of the inspected
systems had zero defects or deficiencies identified.
There are also studies that provide information on
sprinkler system effectiveness in terms of effects on the
consequences from fire, such as fatalities, injuries, or
amount of building floor area consumed by fire. These
studies are discussed in a later section.
Definition of sprinkler system effectiveness
The definition of what constitutes an effective sprin-
kler system operation in a fire event is not consistent
between studies. Marryatt defines “satisfactory” sprin-
kler operation as limiting the damage to the building
and contents to 20% of the total value involved. He
defines “controlled” fires as “those which are extinguished
by the sprinkler system by the time the fire brigade
arrives, or which would be extinguished eventually without
supplementary action by fire brigades or others.” This
definition is slightly misleading as all fires will even-
tually extinguish once they have exhausted all available
fuel supply. (Hall 2010) states that sprinkler effectiveness
should be measured relative to the design objectives of
the system, in most cases limiting fire spread to the room
of origin.
Reporting of fires that do not activate sprinklers
A major source of discrepancy when comparing sprinkler
effectiveness values between studies is how fires where the
sprinkler system is not activated is handled. A sprinkler
system may not activate (ie. one or more sprinkler heads
operating) in a fire for one of the following reasons:
1. the heat released by the fire was insufficient to
activate the sprinkler system (whether or not the
sprinkler system was present in the area of origin), or
2. the fire was large enough to activate a sprinkler
system but a partial sprinkler system was installed
and was not present in the area of fire origin, or
3. the fire was large enough to activate the sprinkler
system and one or more sprinklers were present but
failed to operate.
At one end of the spectrum, (Marryatt 1988) does not
include any fires that did not operate a sprinkler, for any
of the three reasons listed above. Sprinklers were reported
activated in nearly all of the 49 fires that Marryatt consid-
ered the sprinkler system operation to be unsatisfactory,
with the possible exception of one incident where the
sprinkler system (and building) was completely destroyed
in an explosion - in which case water from the broken sup-
ply piping still extinguished the fire. This is one factor that
likely contributes to high reported values of effectiveness,
such as the 99.5% reported by Marryatt.
At the other end, (Juneja 2004) includes in the oper-
ational failures all fires where a sprinkler system was
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installed in the building, including cases where the fire
was too small to operate the system and where the fire is
remote from the sprinkler system. This contributes to the
low sprinkler effectiveness of 70.1% reported by Juneja,
relative to the other studies. To these authors it would
seem that the approach used by Juneja is too punitive.
Reasons for sprinkler systems to fail to operate
Table 10 lists the reported reasons why sprinkler systems
failed to operate in the studies where this information
was available. For studies that combined failures with
ineffective operation, the reported percentage has been
normalised to the total number of failures for compari-
son. The most frequent reason for sprinkler system failure,
ranging from 33% to 100% of the reported failures, is
that the system was shut off. Inappropriate systems, lack
of maintenance, and manual intervention are reported at
similar frequencies from 5% to 33%. Damaged compo-
nents and frozen systems provide the minority of failures,
generally near 2% with one outlier in Power’s study dam-
aged components comprised 2 out of 6 failures, which is
likely a reflection of the small sample size of failures.
Reasons for ineffective sprinkler system operation
Table 11 lists the reported reasons why sprinkler systems
that operated were ineffective, normalised to the total
number of ineffective operations. The most common rea-
son for sprinkler systems to operate ineffectively was that
the water did not reach the fire, ranging from 19% to 55%
of the reported cases. An inappropriate system for the
fire was the second most commonly reported reason, fol-
lowed by not enough water released. These reasons are
inter-related, and could have different root causes. For
example, a partial coverage system may result in any of
these outcomes. A change in occupancy or hazard could
also result in all three outcomes: for example, a change in
fuel package configuration could result in a portion of the
fire being shielded, or a system designed for a light com-
mercial occupancy could be insufficient if the use of the
building is changed to storage of high-hazard materials.
(Hall 2010) noted that NFPA estimates of effective-
ness “exclude partial systems as identified by reason for
failure and ineffectiveness equal to equipment not in area
of fire”. This approach is not likely taken in the other
studies reviewed. It should be noted that reported reasons
for sprinkler systems to operate ineffectively may require
subjective judgement by the reporter.
Number of sprinklers activated
Due to the physical evidence available, the number of
sprinklers activated is a relatively simple parameter to
quantify objectively. However, it is not generally clear how
the number of sprinklers activated relates to the effec-
tiveness of the system. PD7974-7:2003 (British Standards
Institution 2003) discusses this issue, noting that some
studies consider system operations with up to 200 sprin-
klers operating effective, and recommends four activated
sprinklers as a consistent cut-off for effective operation,
stating “no more than four heads operating is the fire
size typically used in a fire engineering study”.Thenum-
ber of sprinklers activated was reported in a number of
the sources that included fire incident data. The avail-
able information is summarised in Figure 4. A boxplot of
the accumulated percentage of fires where the number of
sprinklers or less activated is shown in Figure 5. The box-
plot represents the minimum and maximum percentage
of sprinklers reported activated with the first and third
quartile as the box limits and the median as the horizontal
line in the box. To make the figure easier to read the num-
berofsprinklersactivatedislimitedto10.Thetrendfor
more activated sprinklers can be inferred from Figure 4.
The studies range from 71% to 96% at the PD7974-
7:2003 recommended effective cut off point of four
sprinklers.
Figure 6 plots the reported sprinkler effectiveness per-
centage versus the percent of fires reported with four or
less sprinklers activated. Most studies report a higher fre-
quency of effective sprinkler operation compared with
thefrequencyoffireswherefourorlesssprinklerswere
reported activated, with the exception of the NFPA 2003-
2007 study. This may be a reflection of the changing
occupancies protected by sprinklers, as residential sprin-
kler systems are designed to support the operation of
less sprinklers and more residential buildings are being
equipped with sprinkler systems (Hall 2010).
To extend the concept put forth in PD7974-7:2003 of
using the number of sprinklers activated as a measure of
sprinkler system effectiveness, a comparison was made
between the cumulative number of sprinklers reported
activated required to reach the effectiveness value quoted
each study, where the information was available. This
concept can be most readily explained by an example.
NFPA data from 1925-1964 (Tryon and McKinnon 1969)
reported “satisfactory” sprinkler operation in 96% of fires,
but only 71% of total fires with sprinklers had four or less
sprinklers reported activated. Thus, using the PD7974-
7:2003 criterion of using four or less sprinklers as a
benchmark for effective sprinkler system operation, the
effectiveness from the 1925-1964 NFPA data would be
only 71%, compared to the reported 96%. In order to
include the 96% of fires where sprinklers activated and
operation was reported to be satisfactory, fires with up
to 36-40 sprinklers activated would need to be included.
Figure 7 shows the relationship between the frequency
of effective sprinkler operation and the cumulative num-
ber of sprinklers reported activated where the frequency
equals the effective sprinkler operation frequency. In gen-
eral, studies reporting a higher frequency of effective
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Table 10 Reported reasons for sprinkler systems to fail to operate
Source Years Types of systems Number Percent System Inappropriate Lack of Manual Damaged System
of fires effective shut off system maintenance intervention component frozen
(Tryon and McKinnon 1969) 1925-1964 Not specified 75290 96.2% 63% 15% 15% 3% 2%
(Hall 2006) 1999-2002 All sprinklers Not reported 89.3% 65% 5% 11% 16% 3%
(Hall 2007) 2002-2004 All sprinklers Not reported 90% 66% 10% 10% 20% 2%
(Hall 2010) 2003-2007 All sprinklers 44310 91% 53% 20% 15% 9% 2%
(Hall 2012) 2006-2010 All sprinklers 47520 88% 63% 5% 6% 18% 8%
(US Department of Energy 2004) 1955-2003 Water-based 251 98.8% 33% 33% 33%
(Powers 1979) 1969-1978 High-rise office buildings 254 98.8% 100%
(Powers 1979) 1969-1978 High-rise buildings (excl. office) 1394 98.4% 100%
(Powers 1979) 1969-1978 Low rise buildings 4061 95.8% 85% 12% 3%
(Marryatt 1988) 1886-1986 All sprinklers 9022 99.5% 100%
Mean 94.7% 73% 14% 10% 15% 9% 2%
St. dev. 4.4% 23% 10% 5% 4% 12% N/A
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Table 11 Reported reasons for sprinkler systems to operate ineffectively
Source Years Types of Water did Inappropriate Not enough Manual Damaged Lack of Exposure Faulty Miscellaneous Unknown
systems not reach system for fire water intervention component maintenance fire building
fire released construction
(Tryon and McKinnon
1969)
1925-1964 Not specified 19% 35% 21% 4% 4% 13% 4%
(Hall 2006) 1999-2002 All sprinklers 55% 7% 31% 2% 5%
(Hall 2007) 2002-2004 All sprinklers 41% 14% 29% 6% 4% 6%
(Hall 2010) 2003-2007 All sprinklers 43% 12% 31% 5% 4% 4%
(Hall 2012) 2006-2010 All sprinklers 53% 3% 18% 9% 9% 8%
(US Department of
Energy 2004)
1955-2003 Water-based None reported
(Powers 1979) 1969-1978 High-rise office buildings None reported
(Powers 1979) 1969-1978 High-rise buildings (excl. office) 100%
(Powers 1979) 1969-1978 Low rise buildings 39% 12% 15% 18% 16%
(Marryatt 1988) 1886-1986 All sprinklers 26% 29% 2% 9% 13% 21%
Mean 39% 20% 32% 6% 5% 6% 10% 14% 11% 19%
St. dev. 14% 14% 30% 3% 2% 2% 5% 1% 10% 3%
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30%
40%
50%
60%
70%
80%
90%
100%
1 10 100 1000
Percent of incidents where number of activated
sprinklers reported
Activated sprinklers reported
Marryatt 1886-1986
Frank 2001-2010
Powers 1969-1978 (NY office highrise)
Powers 1969-1978 (NY other highrise)
Powers 1969-1978 (NY lowrise)
DOE 1955-2003
NFPA 1925-1964 (total)
NFPA 1925-1964 (wet)
NFPA 2003-2007 (total)
NFPA 2006-2010 (wet)
NFPA 2006-2010 (dry)
NFPA 2006-2010 (total)
Figure 4 The cumulative percentage of incidents where the number of sprinklers activated were reported.
sprinkler operation required a larger number of acti-
vated sprinklers to achieve the stated effectiveness. This
is potentially a reflection of the subjective criteria used
to define effective sprinkler operation: studies that report
high sprinkler effectiveness may have more inclusive cri-
teria for defining effective sprinkler operation.
Typically sprinkler system water supplies are hydrauli-
cally designed to support a number of sprinklers or sprin-
klered area which is a function of the expected fire hazard
(Standards New Zealand 2007; Tryon and McKinnon
1969). Baldwin discusses the number of instances where
thedesignnumberofsprinklerswereexceededforfires
in the UK from 1967-1968 (Baldwin and North 1971). A
table of the results from this study is shown in Table 12.
Estimates of reduction in fatalities and property damage
Several system-based studies estimate the effect of sprin-
klers on general life safety and property protection
objectives such as the number of fatalities or amount of
property damage reported in fire incident data. Marryatt’s
study included eleven fires where fatalities occurred with
an operating sprinkler system, only one of which occurred
in a fire where the performance of the sprinkler system
was considered ineffective, where an explosion occurred
and broke the supply main to the system (Marryatt 1988).
Of the fires with fatalities in sprinklered buildings, eight
were a result of an explosion or flash fire and the remain-
ing three were victims who were intimate with the point
of ignition.
30%
40%
50%
60%
70%
80%
90%
100%
12345678910
Percent of incidents where number of activated
sprinklers reported
Activated sprinklers reported
Figure 5 Box plot of cumulative percentage of incidents where the number of sprinklers activated were reported (up to 10 sprinklers
activated).
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Marryatt 1886-1986
Powers 1969-1978 (NY
office highrise)
Powers 1969-1978 (NY
other highrise)
Powers 1969-1978 (NY
lowrise)
NFPA 1925-1964 (total)
NFPA 2003-2007 (wet)
NFPA 2003-2007 (dry)
NFPA 2003-2007 (total)
DOE 1955-2003
NZFS 2001-2010
60%
65%
70%
75%
80%
85%
90%
95%
100%
60% 65% 70% 75% 80% 85% 90% 95% 100%
Percent of fires reported as effective
Percent of fires with 4 or less sprinklers reported activated
NFPA 2006-2010 (total)
Figure 6 Reported effective sprinkler operation and the frequency of fires reported where four or less sprinklers operated. Wet and dry
represent wet and dry pipe sprinkler systems, respectively. The uncertainty in the data from (Frank et al. 2012) is shown by the error bars.
(Thomas 2002) estimated effects of fire safety systems
on four objectives including the reduction in fire spread,
civilian fatalities, and firefighter losses in fires where
various combinations of detectors, sprinklers, and pro-
tected construction were present, from historical US
NFIRS data. The effects of the systems were compared to
a “Base Case” where none of the systems were present.
Effectiveness of sprinkler systems was found to vary
between -2.46 for the fire spread objective (reported aver-
age estimated monetary loss was approximately 2.5 times
higher when sprinklers were present compared to the base
case)for Storage occupancy buildings and 1.00 for civilian
fatalities in Hotels and Motels (reported civilian fatalities
were reduced to zero). Negative effectiveness values were
also calculated for detectors and protected construction.
Thomas concluded that sprinklers were generally bet-
ter than detectors and fire-rated construction combined,
while there was a measurable but sometimes small advan-
tage with all three measures compared with instances
where sprinklers were the only system installed.
Thomas also separated NFIRS data for the four
objectives mentioned by occupancy, including Public
Marryatt 1886-1986
Powers 1969-1978 (NY
office highrise)
Powers 1969-1978 (NY
other highrise)
Powers 1969-1978 (NY
lowrise)
NFPA 1925-1964 (total)
NFPA 2003-2007 (wet)
NFPA 2003-2007 (dry)
NFPA 2003-2007 (total)
DOE 1955-2003
NZFS 2001-2010
75%
80%
85%
90%
95%
100%
010203040
Percent of fires reported as effective
Cumulative number of sprinklers reported activated in fires
NFPA 2006-2010 (total)
Figure 7 Reported effective sprinkler operation and the cumulative number of sprinklers reported operating at an equivalent frequency
to the reported effective sprinkler operation frequency. Wet and dry represent wet and dry pipe sprinkler systems, respectively. The uncertainty
in the data from (Frank et al. 2012) is shown by the error bars.
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Table 12 Percentage of fires where the design number of sprinklers was exceeded and where the fire was controlled by
sprinklers, from 1967-1968 UK data reported by (Baldwin and North 1971)
Hazard Number of Design number Design number of Controlled
fires reported of sprinklers sprinklers exceeded by sprinklers
Extra low hazard 30 4 23% 90%
Ordinary hazard 1 8 6 17% 88%
Ordinary hazard 2 91 12 9% 93%
Ordinary hazard 3 476 18 6% 95%
Extra high hazard 14 29 3% 79%
Assembly, Institutional, Apartments, Hotels and Motels,
Offices, Manufacturing, Educational, 1 and 2 Family
Dwellings, Rooming and Boarding, Dormitories, Retail,
and Storage. For sprinklers, he found negative effective-
ness (measures of the four objectives were worse when
sprinklers were present compared to the base case) for
civilian injuries in the Public Assembly, Offices, Manufac-
turing, Educational, Retail, and Storage occupancies; for
firefighter injuries in the Storage occupancy; civilian fatal-
ities in the Educational occupancy; and fire spread (mea-
sured by average monetary loss) in the Storage occupancy.
Thomas indicated that there may be other factors that
influence the apparent effectiveness of the systems consid-
ered in his study. For example, he noted that while civilian
injuries increased in several occupancies where sprinklers
were present, it was impossible to evaluate the severity
of the injuries from the reported data, so it was possible
that while more injuries occurred when sprinklers were
present in some occupancies, many of them may have
been less severe. A potential explanation of the increased
fire losses noted in Storage occupancy buildings offered by
Thomas was that storage buildings with sprinklers may be
on average much larger and have much more value associ-
ated with the building and contents, although he conceded
that this possibility would require more data to verify.
(Melinek 1993b) estimated the number of casualities in
the UK if all fires occurred in sprinklered buildings, by
relating the number of fatalities to the extent of fire spread
in sprinklered and non-sprinklered buildings. It was esti-
mated that the number of fatalities would be reduced
by approximately 50%. Melinek also looked at the effect
of sprinklers on reducing the area affected by fire, and
found that sprinklers had little effect on fires reaching a
size of 3 m2, but reduced the probability of a fire reach-
ing 100 m2or greater area by 80% when they worked
effectively (Melinek 1993a). Melinek also discussed the
potential that less fires may be reported to the fire service
in sprinklered buildings. Based on UK data from 1966 to
1972, it was noted that only 17% of calls to the fire service
from sprinklered buildings were automatic. By assuming
thatthenumberoffirestartsinindustrialbuildingswas
proportional to the product of the number of buildings
and the square root of the mean building area, Melinek
estimated that the fire services responded to 55% of the
fires in sprinklered buildings that would be expected if the
buildings were not sprinklered.
NFPA data from 2003-2007 indicated that sprinklers
increased the probability that flame damage was confined
to the room of origin to 95% compared with 74% for fires
in buildings with no sprinkler systems. The fatality rate
was 83% lower in fires in properties protected by sprin-
kler systems, and total property damage was reduced by
40%-70% depending on occupancy (Hall 2010). The 2010
NFPA report also indicates that the “NFPA has no record
of a fire killing three or more people in a completely sprin-
klered building where the system was properly operating”.
Twenty-fivefiresarelistedwherethreeormorepeople
have been killed in fully sprinklered properties in the US
since 1970. Twenty-two involved an explosion or flash fire
and three were a result of firefighting activities.
Uncertainty in estimates of sprinkler system
effectiveness
The range in both sprinkler component and system data
collected in this paper shows that there is uncertainty in
estimating the effectiveness of sprinkler systems for risk-
informed fire safety design. Four studies have included
suggested distributions and methodology for including
uncertainty in sprinkler system estimates.
(Bukowski et al. 1999) compiled histograms of system
effectiveness estimates from a number of studies. Caution
was given against using single values for estimating the
effectiveness of fire protection systems. Ranges of 88% to
98% for commercial systems and 94% to 98% for general
systems were given by Bukowski.
(Siu and Apostolakis 1988) discussed the uncertainty
involved in using expert judgement to estimate the reli-
ability (or “demand availability” as termed in the origi-
nal paper) of sprinkler systems in specific installations.
A Bayesian approach was used to combine small sets
of directly relevant incident data with partially relevant
data from general populations of sprinklered fire inci-
dent data and system test data. Their work also provides
techniques to account for and assess an expert’s expertise
in supplying data estimates. Data from 16 nuclear facil-
ity sprinklered fires was supplemented with “expert” data
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represented by Industrial Risk Insurers’ sprinkler test data
and NFPA sprinklered fire data with associated bias fac-
tors to estimate a posterior distribution for the reliability
of a sprinkler system in a nuclear facility. The distribution
Sui and Apostolakis arrived at for the base case sprinkler
reliability in a nuclear facility had a mean reliability of 89%
with a standard deviation of 6%.
(Gravestock 2008) recommended uncertainty distribu-
tions for sprinkler system component reliability estimates,
as well as upper and lower bounds for system effective-
ness. Gravestock noted that where information on distri-
bution shape is unknown, but upper and lower bounds are
known, a uniform distribution may be appropriate which
assigns equal probability to all potential values within the
bounds. If the upper and lower bounds are known and
a value of maximum probability is known, a triangular
or PERT distribution may be more appropriate. Grave-
stock recommended using a mean effectiveness of 90% for
sprinkler systems in apartments and 95% for sprinkler sys-
tems in offices, with lower bounds ranging from 46% to
89% and upper bounds ranging from 97% to 99%.
(Frank et al. 2012) estimated the uncertainty in sprin-
kler effectiveness reported in New Zealand Fire Service
fire incident reports from 2001 to 2010. Probability distri-
butions for sprinkler effectiveness from the reported data
were developed using a decision tree approach. Sprinkler
system effectiveness based on the reported data was esti-
mated to be 86% with a standard deviation of 4.6%, using
a normal distribution. Ambiguous reporting noted in the
fire incident data was a major source of uncertainty in
estimating sprinkler effectiveness from this data.
Comparing component-based studies with
system-based studies
While it is difficult to directly compare component-based
studies and system-based studies, a number of observa-
tions can be made. First, the majority of failures reported
in real fires are due to the system being shut off, an
inappropriate system, and manual intervention and these
failures are not generally captured in component-based
studies, although some component-based studies attempt
to. One example is the study by Moelling et al, which
does discuss the probability of inadvertently closed valves
(Moelling et al. 1980). Second, component-based stud-
ies may capture some reasons for ineffective operation,
such as not enough water released in the case of a
pump not operating, but again, the majority of reasons
such as partial systems, inappropriate systems, or man-
ual intervention are not captured in component-based
approaches. However, component-based studies may cap-
ture failures for lack of maintenance or damaged com-
ponents. While data for the exact components used may
not be available, the use of a component-based approach
allows reliability estimates for the specific set of compo-
nent types used in an individual sprinkler system to be
combined.
In most cases, studies presenting sprinkler system
component data do not elaborate on the failure modes
considered. Other than a few exceptions, component reli-
ability is generally considered to be binary, either the
component operates successfully or it fails completely.
Correlations between the failure of components are not
considered: for example, it is possible that multiple
components may fail simultaneously or in close suc-
cession, particularly if poor maintenance practices are
employed. Thus estimating overall system effectiveness
from component-based data is difficult.
System-based studies, by their nature, provide the best
average estimates of overall sprinkler system effectiveness.
However, since fires are relatively rare events, system-
based studies often do not provide detailed information
on specific types of sprinkler systems, specific sprinkler
system configurations, or other systems present. Fires
occur in all ages of buildings, so even new fire incident
data includes old sprinkler system designs. In general, the
specifications or standard that the incident sprinkler sys-
tems were designed to are not available. Maintenance,
inspection, and testing data is also not included, so it is
difficult to estimate the effects of these aspects on system
effectiveness. General details regarding the building of fire
origin such as size, geometry, and construction may not be
documented and changes to the building use and hazard
between the time of design and the incident are not likely
to be recorded. Thus it is difficult to estimate how system
improvements such as upgraded water supplies or pip-
ing networks, or improved inspection, maintenance, and
testing practices, will improve system effectiveness from
system-based studies. In addition, determining whether
a sprinkler system operated effectively or not and the
reasons why it may or may not have can require subjec-
tive judgement on the part of the reporter, which creates
uncertainty in the reported outcome.
Given the limited information available, the recom-
mended approach to estimate effectiveness for a specific
system is to take a distribution of effectiveness for general
sprinkler systems from system-based studies, and to mod-
ify using data from component-based studies. The relative
contribution of each component to system effectiveness
can be estimated from the component data, and then the
effect of making a change to the sprinkler system (such
as improving the water supply or improving inspection)
should then be considered on a comparative basis with the
base system rather than on an absolute basis.
Conclusions and recommendations
Given how common sprinklers are and how long they have
been in use in building fire protection it may be surprising
how little is known regarding their effectiveness. This
Frank et al. Fire Science Reviews 2013, 2:6 Page 18 of 19
http://www.firesciencereviews.com/content/2/1/6
paper has summarised available sprinkler system compo-
nent data and effectiveness estimates for sprinkler sys-
tems from fire incident data studies, with discussion of
the relative merits of each approach and the uncertainty
involved.
Anumberofrecommendationscanbemadefor
estimating the effectiveness of a sprinkler system for
performance-based design. Due to the majority of sprin-
kler failures being related to human error, component-
based study data should not be used exclusively without
comparison to system-based study data. Adjusting sprin-
kler system effectiveness due to a system modification
such as additional water supplies or valve monitoring
should be based on an estimate of the number of failures
observed in real fire incidents that would be prevented
by the proposed change. The modified effectiveness for
the system change can be supported by component-based
data.
One potential application of fire incident system-based
historical studies is that they be used to test the capabil-
ity of models such as fault trees. However, the variations
that exist between the two approaches mean such com-
parisons cannot easily be made. The limited data avail-
able and subjective nature of fire incident data precludes
the use of a single point value for sprinkler effective-
ness in performance-based fire safety design. A range
of values with associated probabilities should be used
to appropriately represent the uncertainty in estimating
sprinkler effectiveness from available data. The sensi-
tivity of the proposed fire safety design to the uncer-
tainty in the sprinkler system effectiveness should be
investigated.
For an estimate of the effectiveness of general fire sprin-
kler systems, the available data indicates that a range of
sprinkler system effectiveness from a minimum of 70%
to a maximum of 99.5% may be possible, or ineffective
sprinkler operation in a range from 3 in 10 fires to 1
in 200. The highest probability of sprinkler system effec-
tiveness appears to be between 90% and 95% or between
1 in 10 and 1 in 20 ineffective sprinkler operations in
fires. For most design purposes, both the extreme upper
and lower limits of reported effectiveness are not likely
applicable due to the definitions used for effective sprin-
kler operation in these studies discussed previously. Data
pertaining to the applicable jurisdiction should also be
considered with greater weight than data from other
jurisdictions due to varying practices of design, installa-
tion, maintenance, and inspection. If using a probabilis-
tic model, a uniform, triangular or PERT distribution
shape may be the most appropriate to use with a peak
between 90% and 95% and upper and lower bounds esti-
mated from the applicable studies for the situation being
considered. An example of a distribution for sprinkler
effectiveness based on New Zealand Fire Service data
from 2001-2010 was developed by (Frank et al. 2012),
which was normally distributed with a mean of 86% and
a standard deviation of 4.6%, although it was noted that
ambiguous reporting contributed to the uncertainty in
estimating sprinkler effectiveness from this data.
For future data collection, the definition of effective
sprinkler system operation should be made clear when
it is being reported as such. Discrete system functions
(e.g. notification and suppression) should be clearly sep-
arated in the data fields. Less subjective measures such
as the number of sprinklers activated as a percentage
of the number of sprinklers for which the system was
hydraulically designed to supply and the number of
sprinklers activated inside and outside the compart-
ment of origin would be useful. Integration with inspec-
tion, testing, and maintenance data would be useful
to provide information on how these factors influ-
ence effectiveness. (Frank et al. 2012) discussed spe-
cific recommendations for improving data collection in
New Zealand, some of which may be suitable in other
jurisdictions.
Competing interests
The authors declare they have no competing interests.
Authors’ contributions
KF collected and collated the data and prepared the manuscript. NG provided
information and insight into New Zealand data. MS helped prepare the
manuscript. CM conceived of the study and provided insight. All authors read
and approved the final manuscript.
Acknowledgements
This work was supported by the New Zealand Ministry of Science and
Innovation, Building Research Levy, and Department of Building and Housing,
and the Natural Sciences and Engineering Research Council of Canada.
Author details
1University of Canterbury, Christchurch, New Zealand. 2Aon, 16th Floor, AMP
Centre, 29 Customs Street West, Auckland, New Zealand.
Received: 8 November 2012 Accepted: 2 October 2013
Published: 20 October 2013
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Cite this article as: Frank et al.:A review of sprinkler system effectiveness
studies. Fire Science Reviews 2013 2:6.
