ISO/TR 24188:2022
(Main)Large outdoor fires and the built environment — Global overview of different approaches to standardization
Large outdoor fires and the built environment — Global overview of different approaches to standardization
This document provides a review of global testing methodologies related to the vulnerabilities of buildings from large outdoor fire exposures. It also provides information on land use management practices. Some of the test methods outlined in this document have been developed in the context of building fires and extrapolated to external fire exposures.
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Standards Content (sample)
TECHNICAL ISO/TR
REPORT 24188
First edition
2022-06
Large outdoor fires and the built
environment — Global overview
of different approaches to
standardization
Reference number
ISO/TR 24188:2022(E)
© ISO 2022
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ISO/TR 24188:2022(E)
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© ISO 2022 – All rights reserved
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ISO/TR 24188:2022(E)
Contents Page
Foreword ........................................................................................................................................................................................................................................iv
Introduction .................................................................................................................................................................................................................................v
1 Scope ................................................................................................................................................................................................................................. 1
2 Normative references ..................................................................................................................................................................................... 1
3 Terms and definitions .................................................................................................................................................................................... 1
4 Ignition scenarios ...............................................................................................................................................................................................3
5 Regulation principle and strategies ................................................................................................................................................ 4
5.1 Japan ................................................................................................................................................................................................................ 4
5.2 California State Building Code (US) ..................................................................................................................................... 5
5.3 NFPA 1144, Standard for Reducing Structure Ignition Hazards from Wildland Fire
(US) ................................................................................................................................................................................................................... 5
5.4 International Wildland Urban Interface Code (IWUIC) ..................................................................................... 5
5.5 France ............................................................................................................................................................................................................. 6
5.6 Australia ....................................................................................................................................................................................................... 6
6 Approach for roofing assemblies .......................................................................................................................................................6
6.1 Japan ................................................................................................................................................................................................................ 6
6.2 North America......................................................................................................................................................................................... 7
6.3 France ............................................................................................................................................................................................................. 7
6.4 Australia ....................................................................................................................................................................................................... 7
7 Approach for exterior walls and facades ................................................................................................................................... 8
7.1 Japan ................................................................................................................................................................................................................ 8
7.2 North America......................................................................................................................................................................................... 8
7.2.1 Fire resistance for exterior walls based on traditional inside-building fire
test methods ........................................................................................................................................................................... 8
7.2.2 Exterior walls outdoor fire exposures............................................................................................................ 8
7.3 France ............................................................................................................................................................................................................. 9
7.4 Australia ....................................................................................................................................................................................................... 9
8 Other building elements .............................................................................................................................................................................. 9
8.1 Vents ................................................................................................................................................................................................................ 9
8.2 Decks ............................................................................................................................................................................................................ 10
8.3 Eaves ............................................................................................................................................................................................................. 10
8.4 Windows.................................................................................................................................................................................................... 10
8.4.1 North America ................................................................................................................................................................... 10
8.4.2 Australia ................................................................................................................................................................................. 10
9 Additional provisions ..................................................................................................................................................................................10
9.1 Reaction-to-fire — California ................................................................................................................................................. 10
9.2 Reaction-to-fire — France......................................................................................................................................................... 11
10 Summary of scenarios and tests ......................................................................................................................................................11
Annex A (informative) Precise description of tests for roof performance defined in the
European Standard CEN/TS 1187 ...................................................................................................................................................14
Bibliography .............................................................................................................................................................................................................................17
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ISO/TR 24188:2022(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).Any trade name used in this document is information given for the convenience of users and does not
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expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.This document was prepared by Technical Committee ISO/TC 92, Fire safety.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.© ISO 2022 – All rights reserved
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ISO/TR 24188:2022(E)
Introduction
Large outdoor fires have the potential to negatively impact the built environment.
Examples of such fires are:— wildland-urban interface (WUI) fires (wildland fires that spread into communities; this type of fire
has become a global problem);NOTE Once a WUI reaches a community, a large urban fire can develop.
— post-earthquake fires (large urban fires that potentially occur after an earthquake);
— tsunami-generated fires (fires potentially generated from tsunamis);— volcano-generated fires (fires potentially generated from volcanic activity); and
— fires that occur in informal settlements.This document provides an overview of approaches to standardization for lessening the destruction on
the built environment caused by such fire exposure. Evacuation is not included as there are no known
approaches to standardization as the present time.© ISO 2022 – All rights reserved
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TECHNICAL REPORT ISO/TR 24188:2022(E)
Large outdoor fires and the built environment — Global
overview of different approaches to standardization
1 Scope
This document provides a review of global testing methodologies related to the vulnerabilities of
buildings from large outdoor fire exposures. It also provides information on land use management
practices. Some of the test methods outlined in this document have been developed in the context of
building fires and extrapolated to external fire exposures.2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
bushfire
unplanned fire in a vegetated area, as opposed to an urban area
Note 1 to entry: Used primarily, but not exclusively, in Australia, New Zealand, and Africa.
Note 2 to entry: It is likely that the term was first used in South Africa and is possibly derived from the Dutch
word ‘bosch’ meaning uncultivated land. In Australia the term was first used in the first half of the 19 century.
The term passed into legislation in the first half of the 20 century, first in the Australian Capital Territory
(Bushfire Act, 1936), Western Australia (A Bush Fires Act, 1937) and New South Wales (Bush Fires Act, 1949).
Note 3 to entry: Definition adapted from Reference [42].3.1.2
direct flame contact
flame impinging on building systems and materials
Note 1 to entry: Direct flame contact is one of the three structure ignition pathways, together with firebrands
and radiant heat.Note 2 to entry: The flames can come either from the main wildfire flames, from burning elements and
ornamental vegetation surrounding structures, or from adjacent structures.Note 3 to entry: Definition adapted from Reference [42].
3.1.3
evacuation
dispersal or removal of people from dangerous areas and their arrival at a place of relative safety
Note 1 to entry: Definition taken from Reference [42].© ISO 2022 – All rights reserved
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ISO/TR 24188:2022(E)
3.1.4
post-earthquake fire
fire which occurs after an earthquake
3.1.5
firebrand
airborne object capable of acting as an ignition source and carried for some distance in an airstream
Note 1 to entry: Firebrands are also sometimes referred to as flying brands or brands.
Note 2 to entry: Firebrands are similar to embers but with a slight distinction: ember refers to any small, hot,
carbonaceous particle and when embers have the capability of setting additional fires, they become firebrands.
Note 3 to entry: The aerodynamic properties of firebrands is an important characteristic requiring consideration.
Note 4 to entry: Firebrands or embers can be burning, flaming or smouldering.Note 5 to entry: Definition adapted from Reference [42].
3.1.7
informal settlement
unplanned settlement or area where housing is not in compliance with current planning and building
regulations (unauthorized housing)[SOURCE: Glossary of Environment Statistics, Studies in Methods, Series F, No. 67, United Nations, New
York, 1997]3.1.8
large outdoor fire
urban fire, tsunami-generated fire, volcano-generated fire, WUI fire, wildland fire, or informal
settlement fire, where the total burnout area is significant3.1.9
spot fire
fire caused by flying firebrands at a distance from the original fire
3.1.10
tsunami-generated fire
fire caused by tsunami, typically by burning elements contained in the flood waters
3.1.11urban fire
fire which occurs in an urbanized area
3.1.13
volcano-generated fire
fire caused by volcanic eruption
3.1.14
wildland
land that either has never suffered human intervention or has been allowed to return to its natural
state, or that is managed for forestry or ecological purposes[SOURCE: ISO/TS 19677:2019, 3.2]
3.1.15
wildland fire
fire occurring in peat, forests, scrublands, grasslands or rangelands, either of natural origin or caused
by human interventionNote 1 to entry: Used primarily, but not exclusively, in North America.
[SOURCE: ISO/TS 19677:2019, 3.3, modified — reference to "peat" added and Note 1 to entry added.]
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3.1.16
wildland firefighting
suppressive action involving a fire in forests, scrublands, grasslands or rangelands
3.1.17wildland-urban interface
WUI
area where structures and other human development adjoin or overlap with wildland
[SOURCE: ISO/TS 19677:2019, 3.4]3.1.18
wildland-urban interface community
WUI community
community where humans and their development meet or intermix with wildland fuel
Note 1 to entry: Definition adapted from Reference [45].
3.1.19
wildland-urban interface fire
WUI fire
wildland fire that has spread into the wildland-urban interface (WUI)
Note 1 to entry: It is also possible for fires to start in the wildland-urban interface (WUI) and spread into the
wildland.3.1.20
wildland-urban interface firefighting
WUI firefighting
suppressive action involving a fire in the wildland-urban interface (WUI) where the action, tactics and
equipment used can differ from urban firefighting4 Ignition scenarios
It is important to understand that large outdoor fires involve the interaction of topography, weather,
vegetation and structures. Large outdoor fires differ from enclosure fires in several ways; most notably
the fire spread processes are not limited to well-defined boundaries, as is the case of traditional building
or enclosure fires. Wildland firefighting and WUI firefighting techniques, as well as fire mitigation,
also differ in their nature, application and in terms of the distances involved in such situations. At the
interface, the interaction of buildings, construction products used, and urbanization rules are also key
parameters. Reference [32] gives a good overview of these phenomena. There are three ways in which
ignition can occur:— Direct flame contact — This is the aspect usually managed by fire tests from building regulations.
— Thermal radiation — The probability of ignition depends on the distance and time of exposure. This
can occur at distances of tenths of meters.— Firebrands — The probability of ignition depends on the accumulation. Spot fires can occur at long
distances (several hundred meters).A combination of any of these three points is also possible. Direct flame contact and thermal radiation
act in combination as a flame exists and emits thermal radiation. Direct flame contact and firebrands
can also act in combination while direct flame contact is likely dominant. Thermal radiation and
firebrands can act in combination as shown in Figure 1.© ISO 2022 – All rights reserved
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ISO/TR 24188:2022(E)
Key
1 direct flame contact
2 thermal radiation
3 firebrands
4 thermal radiation and firebrands
Figure 1 — Fire propagation modes in large outdoor fires (from Reference [32])
5 Regulation principle and strategies
5.1 Japan
[25]
The Building Standard Law (BSL) of Japan aims to cover the threat of large urban fires. According
to the BSL, there are two major fire tests conducted in Japan in the context of preventing urban fire
spread: a roof test and a fire resistance test for exterior walls.The purpose of the BSL is to safeguard the life, health and property of people by providing minimum
standards concerning the site, construction, equipment and use of buildings, and thereby to contribute
to the furtherance of the public welfare. To prevent fires from spreading from one building to the next
and to minimize the occurrence of urban fires, buildings located in "fire protection zones (FPZs)",
"quasi-fire protection zones (QFPZs)", and "cities under Article 22” are required to conform to the BSL.
Figure 2 illustrates the basic philosophy of zoning. While no scientific research has yet been carried out
to determine the efficacy of these regulations, due at least in part to the regulations, large urban fires
are a relatively rare occurrence in Japan today, and are most likely to occur under extreme conditions
(in themselves rare), such as those following a major earthquake or in extremely high winds.
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ISO/TR 24188:2022(E)
Key
1 fire protection zone
2 quasi-fire protection zone
3 city under Article 22
4 station
5 railway
Figure 2 — Zoning concept according to BSL of Japan (from Reference [25])
5.2 California State Building Code (US)
California refers to California Building Code, Title 24, Part 1, Chapter 7A Materials and Construction
Methods for Exterior Wildfire Exposure, as well as Chapter 49, Requirements for Wildland-Urban
Interface Areas. The following California State Fire Marshal (SFM) Test Standards are described: 12-7A-
[6] [20] [18] [14] [21]1, 12-7A-2, 12-7A-3, 12-7A-4, 12-7A-5.
5.3 NFPA 1144, Standard for Reducing Structure Ignition Hazards from Wildland Fire
(US)[50]
The National Fire Protection Association (NFPA) published the current edition of NFPA 1144 in
2018. This standard can serve as a model for adoption (in total or with amendment) by local building
codes. The scope of the document ranges from assessing fire hazard in the structure ignition zone to
building design, location and construction. Building components covered include: roof, exterior walls,
openings (including windows and doors), chimneys, and accessory structures. Sample qualitative and
quantitative hazard assessment methodologies are included in the Annex. In the 2022 revision process
[48] [49]this document is to be combined with NFPA 1141 and NFPA 1143 to form a single document, NFPA
1140.5.4 International Wildland Urban Interface Code (IWUIC)
[47]
The International Code Council (ICC) published the current edition of the IWUIC in 2018. This model
ranges in scope from water supply and vehicles access to building construction and fire protection
requirements. Appendix sections provide additional information on topics including: vegetation
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management, fire hazard severity assessment forms and “self-defence mechanisms”. Notable is the
Ignition-Resistance Construction system described in Chapter 5. The system contains three class levels
(Class 1, Class 2 and Class 3) and specifies construction requirements for each. Class 3 requires the
nominally most ignition-resistant materials and construction. Several standards and test methods
from other organizations including ASTM, NFPA and UL are referenced.5.5 France
The French standards and regulations are mainly dedicated to design (or certification by standard
tests) fire resistance or reaction to fire of construction products against compartment fire or
traditional building fires. Nevertheless, standards or performance requirements concern the design of
[51]products against external fire. The Eurocode EN-1991-1-2 provides a dedicated external fire curve
(temperature-time) pertinent for exposure of structural construction elements against external flame
coming out from windows of other compartments, but this standard is not used for classification tests.
[37]The European Standard EN-1363-2 indicates that this curve can be considered for outside fire, but in
practice it is also not employed for classification tests.For wildland-urban interface (WUI) fires, no standards specify the fire exposure explicitly. Instead,
one finds two different categories of approaching standard tests are reviewed in detail in the following
subclauses:— tests for some structural elements (roofs and facades essentially) which are ad hoc tests, allowing
to test reaction and resistance to fire with ad hoc fire curves and ad hoc acceptance criteria.
— tests for other structural elements which are tests with standard generic fire curves and acceptance
criteria.5.6 Australia
The Australian National Construction Code (NCC) has performance provisions that address buildings
that are located in a designated bushfire-prone area (WUI fire-prone area). The NCC has three volumes—
the Building Code of Australia is Volume One and Volume Two and the Plumbing Code of Australia is
[54]Volume Three. Bushfire areas of the NCC 2019 Volume Two is satisfied if the building is constructed
[52]in accordance with either 1) AS 3959 or 2) NASH Bushfire Standard — Non-combustible building
[44]cavity construction in bushfire areas. AS 3959 contains normative reference to the two standards
[9] [8]in the Australian Standard AS 1530.8.1 and AS 1530.8.2 test standards. The testing standards have
[41]been applied to roof, wall and other assembly types. Baker et al. provide a comprehensive overview
of the regulatory framework of Australia for interested readers.6 Approach for roofing assemblies
6.1 Japan
Roof tests in Japan are based on ISO 12468-1, with a minor modification of the size of the cribs placed
on the surface of roof specimens. Different cribs are used for the roofs located in different zones. For
the roof specimens which will be constructed in FPZs and QFPZs, total size of crib is (80 × 80 × 60) mm,
which is composed by lumbers, and each configuration is (19 × 19 × 80) mm. On the other hand, for the
[25]roof specimens in “Cities under Article 22 of BSL (Building Standard Law)” or “Low-flame-spread
roof area”, lumber is used, where the size is (40 × 40 × 40) mm, which conforms to the specifications
of “Brand B” in ISO 12468-1. This difference on firebrands stems from the assumption that buildings
in FPZs and QFPZs are closely adjacent to each other and can therefore produce larger firebrands than
fires in “Cities under Article 22 of BSL”. Furthermore, the roofs of the buildings located in the FPZ and
QFPZ can be less vulnerable to the attacking of flying firebrands in case of urban fire than those in
“Cities under Article 22 of BSL”. The same criteria are applied when interpreting the results of tests for
all specimens, even when different crib configurations are used. There are three major elements in the
criteria, namely, 1) fire propagation (not reaching to the edge of specimen), 2) integrity (no flame on the
reverse side of the specimen), and 3) defect [no through-hole larger than (10 ×10) mm]. Furthermore,
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ISO/TR 24188:2022(E)
non-combustible roof tiles do not even need to be tested. Recent joint USA/Japan research has shown
[27]these methods do not simulate firebrand showers seen in large outdoor fires.
6.2 North America
There are a few existing test methods that measure the ability of a roof assembly to resist the passage of
[10]fire into the attic and spread of fire on the roof surface. In Canada, CAN/ULC-S107 is used to measure
[17] [11]the roof performance, which follows a similar procedure as ASTM E-108 , UL 790 and NFPA
[12]276 . During the test the assembly is exposed to flames from a calibrated burner. For combustible
roof decks, a series of burning standard brands and an intermittent flame exposure are also required.
The roof assemblies are classified based on their effectiveness against fire exposure, flammability/
combustibility, and degree of fire protection provided to the roof deck, and propensity to produce
flying brands. They provide three classes, Class A, Class B, and Class C. Class A is the most resistant and
Class C the least resistant. Recent joint US/Japan research has shown these methods do not simulate
[27]firebrand showers seen in large outdoor fires.
6.3 France
[34]
CEN/TS 1187 is a collection of 4 separate tests, and in France, test 3 is applied. Even if a roof is
validated according to test 3, it is not considered valid in the 3 other tests. Details are provided in
Annex A.Test 3 has an ad hoc experimental setup, including firebrands positioned at defined positions on the
roof before being flamed, low atmospheric wind conditions (around 3 m/s) possibly propagating the
fire to the roof components, and a radiative heating from a radiant panel at about 12,5 kWm . The
firebrands are composed of 4 pieces of wood assembled together to build a crib of (55 × 55 × 32) mm,
pre-conditioned in temperature and relative humidity. This setup has been initially designed not to
represent wildfire firebrands, but rather to represent burning pieces of timber or construction wooden
items, which have been projected from a neighbouring building fire. A 30 min fire exposure is performed.
[35]Classification criteria (A, B, … roof) are given by the adjacent standard EN 13501-5 :2005+1 :2009.
Precise details on this test design, as well as comparison with the other tests, are found in Annex A.
6.4 Australia[8]
AS 1530.8.2 is the Australian test standard for WUI exposure. AS 1530.8.2 is for severe fire exposure
or direct flame impingement (BAL FZ). During AS 1530.8.2, a representative element of construction
or combination of elements is exposed to the standard fire curve. The test duration is 90 min which
includes a 30-min exposure to the standard fire and a 60-min monitoring period.[9]
For lower e
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