ISO/TR 24188:2025

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.

Grands incendies extérieurs et environnement bâti — Vue d'ensemble des différentes approches en matière de normalisation

General Information

• Status: Published
• Publication Date: 10-Feb-2025
• ICS: 13.220.01 - Protection against fire in general
• Technical Committee: ISO/TC 92 - Fire safety
• Drafting Committee: ISO/TC 92/WG 14 - Large outdoor fires and the built environment
• Current Stage: 6060 - International Standard published
• Start Date: 11-Feb-2025
• Completion Date: 11-Feb-2025

Relations

• Revises: ISO/TR 24188:2022 - Large outdoor fires and the built environment - Global overview of different approaches to standardization
• Effective Date: 02-Mar-2024

Overview

ISO/TR 24188:2025 - Large outdoor fires and the built environment - Global overview of different approaches to standardization is a Technical Report from ISO/TC 92 that reviews global testing methodologies and land use management practices related to the vulnerabilities of buildings to large outdoor fires. The report surveys ignition scenarios (wildland‑urban interface/WUI fires, post‑earthquake fires, tsunami‑ or volcano‑generated fires, and informal settlement fires), summarizes how different jurisdictions regulate ignition risk, and catalogs test approaches for building elements exposed to external fire hazards.

Key topics and technical scope

• Ignition scenarios: three primary mechanisms are described - direct flame contact, thermal radiation, and firebrands - including combinations and implications for spotting and fire spread.
• Regulation principles and strategies: comparative overview of national/regional approaches (examples include Japan, California building code, NFPA 1144, IWUIC, France, Australia).
• Standard test approaches: overview and classification of tests relevant to external exposures, including methods for roofing assemblies, exterior walls and facades, and other elements (vents, decks, eaves, windows).
• Reaction‑to‑fire provisions: noted jurisdictional differences (e.g., California, France) in how reaction‑to‑fire testing is applied to reduce structure ignition hazards.
• Land use management practices: how zoning, buffer zones and urban planning interact with building‑level measures to mitigate large outdoor fire risk.
• Informative annexes: examples such as the European CEN/TS 1187 roof test description are provided for reference.

Practical applications

ISO/TR 24188:2025 is a guidance and review document useful for:

• Building code and standards developers seeking cross‑jurisdictional perspectives on external fire testing and regulation.
• Fire safety engineers and researchers evaluating building vulnerability, designing mitigation measures, or developing test methods for large outdoor fires.
• Architects and manufacturers of roofing, cladding and facade systems requiring awareness of external exposure risks and relevant test approaches.
• Urban and land‑use planners integrating zoning, defensible space and fuel management to reduce WUI and large outdoor fire impacts.
• Insurance and risk assessment professionals estimating exposure and losses from external fire scenarios.

Related standards and references

The report cross‑references national codes and existing standards such as NFPA 1144, International Wildland Urban Interface Code (IWUIC), CEN/TS 1187, and ISO/TS documents (e.g., ISO/TS 19677) as context for global standardization approaches.

ISO/TR 24188:2025 is a practical resource for harmonizing test practices and informing policy decisions to reduce the impact of large outdoor fires on the built environment.

Standards Content (Sample)

Technical
Report
ISO/TR 24188
Second edition
Large outdoor fires and the built
2025-02
environment — Global overview
of different approaches to
standardization
Grands incendies extérieurs et environnement bâti —
Vue d'ensemble des différentes approches en matière de
normalisation
Reference number
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
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) .4
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 .5
5.6 Australia .5
6 Standard tests approaches . 5
6.1 Overview .5
6.2 Approach for roofing assemblies.6
6.2.1 Japan .6
6.2.2 North America .6
6.2.3 France .6
6.2.4 Australia .6
6.3 Approach for exterior walls and facades .7
6.3.1 Japan .7
6.3.2 North America .8
6.3.3 France .8
6.3.4 Australia .8
6.4 Other building elements .9
6.4.1 Vents .9
6.4.2 Decks .9
6.4.3 Eaves .9
6.4.4 Windows .10
7 Additional provisions .10
7.1 Reaction-to-fire — California .10
7.2 Reaction-to-fire — France.10
8 Summary of scenarios and tests .10
Annex A (informative) Precise description of tests for roof performance defined in the
European Standard CEN/TS 1187 .13
Bibliography .16

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and 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.
This second edition cancels and replaces the first edition (ISO/TR 24188:2022), which has been technically
revised.
The main changes are as follows:
— various term entries in Clause 3 have been modified;
— Figure 2 has been replaced with a new diagram;
— the Bibliography has been updated.
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.

iv
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 fire 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. Some of the test methods outlined in this document have
been developed in the context of building fires and extrapolated to external fire exposures. Evacuation is
not included as there are no known approaches to standardization as the present time.

v
Technical Report ISO/TR 24188:2025(en)
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.
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: For further information, see Reference [42].
3.1.2
direct flame contact
flame impinging on building systems and materials
Note 1 to entry: For further information, see Reference [43].
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: For further information, see Reference [44].
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: For further information, see Reference [45].

3.1.6
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,
[46]
1997]
3.1.7
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 significant
3.1.8
spot fire
fire caused by flying firebrands at a distance from the original fire
3.1.9
tsunami-generated fire
fire caused by tsunami, typically by burning elements contained in the flood waters
3.1.10
urban fire
fire which occurs in an urbanized area
3.1.11
volcano-generated fire
fire caused by volcanic eruption
3.1.12
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]
3.1.13
wildland fire
fire occurring in peat, forests, scrublands, grasslands or rangelands, either of natural origin or caused by
human intervention
Note 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.]
3.1.14
wildland firefighting
suppressive action involving a fire in forests, scrublands, grasslands or rangelands
3.1.15
wildland-urban interface
WUI
area where structures and other human development adjoin or overlap with wildland
Note 1 to entry: A community based in such an area, in which humans and their development meet or intermix with
[48]
wildland fuel, is referred to as a WUI community.
Note 2 to entry: A fire that spreads to a WUI is referred to as a WUI fire. Suppressive action in relation to such a fire
is referred to as WUI firefighting, and can involve different actions, tactics and equipment compared to those used in
urban firefighting.
[SOURCE: ISO/TS 19677:2019, 3.4, modified — Notes to entry have been added.]

4 Ignition scenarios
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 WUI, the interaction of buildings, construction
products used and urbanization rules are also key parameters. Reference [32] provides an 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 metres.
— Firebrands — The probability of ignition depends on the accumulation. Spot fires can occur at long
distances (several hundred metres).
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.
Key
1 direct flame contact
2 thermal radiation
3 firebrands
4 thermal radiation and firebrands
SOURCE Reference [32], reproduced with the permission of the authors.
Figure 1 — Fire propagation modes in large outdoor fires

5 Regulation principle and strategies
5.1 Japan
[25],[33]
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 of BSL” 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.
Key
1 fire protection zone
2 quasi-fire protection zone
3 cities under article 22 of BSL
4 station
5 railway
Figure 2 — Zoning concept according to BSL of Japan
5.2 California State Building Code (US)
California refers to the 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
[6]
Areas. The following California State Fire Marshal (SFM) Test Standards are described: 12-7A-1 , 12-7A-
[20] [18] [14] [21]
2 , 12-7A-3 , 12-7A-4 , 12-7A-5 .

5.3 NFPA 1144, Standard for Reducing Structure Ignition Hazards from Wildland Fire (US)
[53]
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, this document was combined with
[51] [52] [54]
NFPA 1141 and NFPA 1143 to form a single document, NFPA 1140.
5.4 International Wildland Urban Interface Code (IWUIC)
[50]
The International Code Council (ICC) published the current edition of the IWUIC in 2021. 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 management, fire hazard
severity assessment forms and “self-defence mechanisms”. The Ignition-Resistance Construction system
described in Chapter 5 is notable: 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 products against external
[55]
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. The European Standard EN-1363-
[37]
2 indicates that this curve can be considered for outside fire, but in practice it is also not employed for
classification tests.
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 Volume
[58]
Three. Bushfire areas of the NCC 2019 Volume Two is satisfied if the building is constructed in accordance
[56]
with either AS 3959 or the NASH Bushfire Standard — Non-combustible building cavity construction
[44] [9]
in bushfire areas. AS 3959 contains normative references to the Australian AS 1530.8.1 and AS
[8]
1530.8.2 test standards. The test standards have been applied to roof, wall and other assembly types. For
a comprehensive overview of the regulatory framework of Australia, see Reference [41].
6 Standard tests approaches
6.1 Overview
For wildland-urban interface (WUI) fires, no standards specify the fire exposure explicitly. Instead, 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
reaction and resistance to fire to be tested 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.
6.2 Approach for roofing assemblies
6.2.1 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. For the roof specimens in “Cities under
[25]
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
in 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:
1) fire propagation (not reaching to the edge of specimen);
2) integrity (no flame on the reverse side of the specimen);
3) defect [no through-hole larger than (10 ×10) mm].
Non-combustible roof tiles do not need to be tested.
Recent joint US/Japan research has shown these methods do not simulate firebrand showers seen in large
[27]
outdoor fires.
6.2.2 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 the
[17] [11] [12]
roof performance, which follows a similar procedure as ASTM E-108, UL 790 and NFPA 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/
[27]
Japan research has shown these methods do not simulate firebrand showers seen in large outdoor fires.
6.2.3 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
−2
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. Classification criteria
[35]
(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.
6.2.4 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 exposure levels, another standard, AS 1530.8.1 , is used, which exposes the specimen to a radiant
heat, burning firebrands and burning debris. AS 1530.8.1 provides standard test methods to determine
the performance when a specimen is exposed to radiant heat, firebrands and burning debris. Exposure
to firebrands is simulated by application of a small gas flame and exposure to burning debris is simulated
by wood cribs. The radiant heat rapidly rises initially until it reaches a specified maximum radiant heat
2 2 2 2
of either 12,5 kW/m , 19 kW/m , 29 kW/m , or 40 kW/m depending on the severity of exposure. The
maximum radiation is maintained for two minutes followed by a gradual decay period. The total radiant
heat exposure period is 10 minutes. Overall, the Australian approach is more representative of the WUI
exposure with some shortcomings; the main one is the lack of wind during the tests. Radiation exposure is
more representative of the approaching wildfire.
A successful testing outcome from either of these testing methods is deemed to be sufficient evidence of
conformance to the standard up to and including the particular exposure level to which it was tested. In
addition to this testing conformance, the roof exterior is required to be non-combustible, and the NASH
standard also requires the roof internals to be non-combustible.
6.3 Approach for exterior walls and facades
6.3.1 Japan
Ordinary wall furnaces (3 m × 3 m) are used in Japan for the fire resistance tests following ISO 834-1
standard fire. Regarding the traditional classification system of fire resistance in Japan, there are four
different classes:
1) fire-resistive construction,
2) quasi-fire-resistive construction,
3) fire preventive construction, and
4) quasi-fire preventive construction.
Among these, especially 3) fire preventive construction, and 4) quasi-fire preventive construction are the
performance required for an exterior wall to restrict the spread of a normal fire that starts in the area
surrounding a building, for 30 min in case of 3), and for 20 min in case of 4). Regarding these two classes,
only stability and insulation, (not integrity), are counted for evaluating the fire resistance of exterior walls.
For reference, regarding the other two classes, 1) fire-resistive construction, is the performance required for
the building parts to prevent a normal fire from causing both the collapse of the building and the spread of
fire even after the end of a normal fire, and 2) quasi-fire-resistive construction, is the performance required
for the building parts to prevent a normal fire from causing both the collapse of the building and the spread
of fire until the end of a normal fire.
Additionally, another standard relating to building façade fire safety in Japan is JIS A 1310 “Test method
[26]
for fire propagation over building façades”. JIS A 1310 is a screening method for determining the fire
propagation of products and constructions of a building façade when exposed to flames ejected from the
building opening. The primary aim of JIS A 1310 is to assess the vertical fire propagation over facades. But,
it can be partially applied for evaluating the potential horizontal fire spreading from the building where the
façade is burning to its adjacent building, because it is prescribed by JIS A 1310 to install the heat flux meter
at 2 m horizontally separated from the façade specimen. Additionally, its measured heat flux data can be
helpful for fire engineers to technically extrapolate whether the adjacent building could be ignited or not.
According to the current Building Standard Law of Japan, JIS A 1310 is not mandatory but voluntary, and is
used for research and development purposes.

6.3.2 North America
6.3.2.1 Fire resistance for exterior walls based on traditional inside-building fire test methods
[1] [2] [3] [4]
Standards CAN/ULC S101 , ASTM E119 , UL 263 , and NFPA 251 describe the standard method
of determining the fire resistance of building components. During fire resistance tests, the assembly is
exposed to heat from a furnace whose temperature follows a specific time-temperature curve. The assembly
fails if the fire passes through the assembly, or the temperature of the unexposed side rises by a certain
amount or if the assembly collapses. Since these tests were developed to represent the fire severity of a
compartment fire, they impose a very high temperature (which follows a standard time-temperature curve
reaching approximately 1 100 °C at 2 h) which is not representative of an external transient fire source.
In Canada, the National Building Code of Canada (NBCC) imposes a certain fire resistance rating for walls.
When fire resistance ratings are required for an exterior wall assembly, the exposure to CAN/ULC-S101 is
only required to be assessed from the interior of the building to the outside. The NBCC does not require fire
resistance ratings to be determined from the exterior to the interior. Other measures are used to limit the
fire hazard posed by materials used on the exterior of buildings.
6.3.2.2 Exterior walls outdoor fire exposures
[6] [7]
Standards SFM 12-7A-1 and ASTM E2707 utilize a diffusion burner to expose the wall to a short 10-min
exposure to a 150 kW fire. The test attempts to simulate a scenario where an indirect exposure of flame
impingement occurs as a result of ignition of plants, trash, a deck or other combustible materials beside
the wall. Unless fire resistance of a longer period is also prescribed in addition to this test, the test does not
apply to a scenario where the building is exposed to a large radiation source for a long duration of time, such
as the burning of an adjacent building.
6.3.3 France
[36]
Façades are covered by LEPIR2 test (National decree of 10-09-1970). This French specification is
currently part of an ongoing work of EU harmonization. The current façade test is a large-scale test
performed on façade mock-ups. Its field of application is to all façade systems (including testing of windows).
Its setup includes a two-level façade, with fire starting in the lower compartment (600 kg of wood cribs),
and openings at the two levels (no glass in the generic setup). A 30-min fire exposure is performed. Then,
requirements regarding fire spread through façades (external surface but also through cavity, facade floor-
junction.) need to fulfil rules based on available combustible mass calculations and technical arrangements
about installation (C+D rules).
[37]
Exterior walls: Although EN-1363-2 was initially designed for the characterization of external flame
temperatures of compartment fire, it can also be used to design fire curve of “natural” external fire, although
38]
a link to the thread observed in real wildland fires is questionable. Internal fire curve (EN-1363-1 ) is
used by default to test structural elements in fire resistance (REI criteria). It is based on ISO 834-1, which
reflects the fire in compartment context. Some local prescriptions ask for such a curve to be applied to a
building envelope close to wildland, even if the relation between this standard exposure and the real fire is
questionable in terms of intensity and time.
6.3.4 Australia
[8]
AS 1530.8.2 is the Australian test standard for WUI exposure. Specifically, AS 1530.8.2 is for severe fire
exposure or direct flame impingement (BAL FZ). In AS 1530.8.2, a representative element of construction or
a 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 exposure levels, AS 1530.8.1 is used, which exposes the specimen to a radiant heat, firebrands
and burning debris. AS 1530.8.1 provides standard test methods to determine the performance when a
specimen is exposed to radiant heat, firebrands and burning debris. Exposure to firebrands is simulated
by application of a small gas flame and exposure to burning debris is simulated by wood cribs. The radiant
heat rapidly rises initially until it reaches a specified maximum radiant heat of either 12,5 kW/m , 19 kW/
2 2 2
m , 29 kW/m , or 40 kW/m depending on the severity of exposure. The maximum radiation is maintained
for 2 min followed by a gradual decay period. The total radiant heat exposure period is 10 min. Overall, the

Australian approach is more representative of the WUI exposure with some shortcomings: the main one is
the lack of wind during the tests. Radiation exposure is more representative of the approaching wildfire.
A successful testing outcome from either of these testing methods is deemed to be sufficient evidence of
conformance to the standard up to and including the particular exposure level to which it was tested. In
addition, the NASH standard also requires the whole wall assembly to be non-combustible.
6.4 Other building elements
6.4.1 Vents
[13]
The US refers to ASTM E2886. While protecting roofs by ignition-resistant materials can protect the
combustible materials in the attic, the entry of firebrands through vents or other openings can compromise
[13]
the effectiveness of the fire protection system. ASTM E2886 attempts to measure the performance of
vents to resist the entry of firebrands and direct flames. During the firebrand test, a flow of generated
firebrands are pulled using a fan to pass through a vent. The firebrand generator consists of a rotating
steel mesh tumbler. Burning Class C firebrands are placed inside the rotating tumbler and generated by
the agitation of the brands and steel nuts that pass the perimeter. Steel mesh is transported by the flow of
air through the vent. If the vent prevents the ignition of cotton pads which are located at the end, it passes
the test. US/Japan experiments form the scientific basis for this test method, and a detailed comparison
[28]
was undertaken with ASTM to develop this test method. Flame intrusion is evaluated separately using
different test procedures.
6.4.2 Decks
[14] [15] [16]
The standards concerned in North America are SFM 12-7A-4, ASTM E2632, and ASTM E2726.
Combustible decking material during a WUI fire event represents a vulnerable section of a building. Since
decks are attached to the building, ignition of decks could result in the spread of fire to the building itself.
Firebrands from the wildfire could accumulate under or within the crevices of the deck and result in the
ignition of the deck. There are several standard test methods for decks. The California building code has
adopted SFM 12-7A-4 for this purpose. The test exposes a 60 cm × 60 cm (24 inch × 24 inch) sample of the
deck to a either a flame (SFM 12-7A-4A) or a burning brand (SFM 12-7A-4B). Two scenarios are considered: in
the first one it is assumed that the accumulation of firebrands has resulted in a fire under the deck, and the
second scenario assumes the firebrands are accumulated over the deck. During the deck flame test the deck
is exposed to a flame of 80 kW for 3 min, equivalent to 1 kg of paper. The sample fails if there is runaway
combustion, structural collapse, or flaming dripping materials. The test procedure requires the sample to be
observed for 40 min after the flame exposure.
The ASTM E2632 test method is almost identical to SFM 12-7A-4A. In SFM 12-7A-4B/ASTM 2726, a standard
[17]
burning brand (standard brand of ASTM E108 ) is placed over the deck while a fan blows an airflow
of approximately 5,4 m/s (12 mph) over the specimen and the sample is observed for 40 min for signs of
sustained flaming or falling brands. In all tests, the samples need to be exposed to conditions of accelerated
aging or weathering to create a more realistic representation of the actual deck in the test. Recent firebrand
[29-31]
shower research has shown these tests are not adequate for wind-driven firebrand exposure.
6.4.3 Eaves
Eaves or similar projections are vulnerable to ignition, namely because heat partially accumulates under
the eave and the material used for the construction of eaves cannot be as fire resistant at the roofing and
[18]
exterior walls. Open eaves are a particularly weak point for entry of flames or firebrands. SFM 12-7A-3
[19]
or ASTM E2957 both expose a 609 mm projection to a flame of 300 kW for 10 min. The sample is then
observed for another 30 min to monitor the existence of glowing or flaming on the unexposed side of the
specimen.
6.4.4 Windows
6.4.4.1 North America
[20]
California refers to SFM 12-7A-2. In order to assess the performance of windows exposed to direct flames,
SFM 12-7A-2 uses a 150 kW, 100 mm × 1 000 mm diffusion burner under the target window. The specimen
is exposed to the flame for 8 min. This test simulates a scenario where a flame is burning a combustible
material around the building and under a window.
6.4.4.2 Australia
[8] [9]
For radiation exposure of windows, AS 1530.8.2 or AS 1530.8.1 can be considered.
7 Additional provisions
7.1 Reaction-to-fire — California
[21]
Ignition-resistant material is defined in SFM 12-7A-5. Any material designated as ignition resistant is
[49]
required to pass a 30-min ASTM E84 test. ASTM E84 was not developed by the SFM of California but is a
legacy standard test method, also known as the Steiner Tunnel test method.
7.2 Reaction-to-fire — France
[39]
Reaction-to-fire of construction products according to EN 13501-1 is requested for all products listed
[57]
in the EU Construction Product Directive . For the other elements, such as sun blinds, curtains, etc, M-
[40]
classification , formerly the French reaction-to-fire provisions, are still applicable; some requirements are
prescribed locally in areas subject to possible wildland fire attack.
8 Summary of scenarios and tests
Table 1 summarizes which scenario of fire is modelled by each standard test reviewed in the previous
clauses, detailed according to three different exposures on buildings: radiative effect, firebrands and direct
flame contact (wind effect).
Table 1 — Summary of test methods
Tested Country Method Radiative effect Firebrands Wind effect Others
structural scenario scenario scenario
element
Roofs Japan ISO 12468-1 No Cribs placed on Yes. The wind —
roof surface, speed is set to
of different 3,0 m/s.
types according
to a building
protection zone
criteria (FPZ,
QFPZ, “Low-
flame-spread”)
USA / CAN/ULC- Flames from a cali- Burning stand- Yes. The spread —
[10]
Canada S107 brated burner ard brands, of flame test
[17] is conducted
ASTM E108 Intermittent /
at a 5,4 m/s
[11] cyclic flame
UL 790
(12 mph) wind
exposure test
[12]
NFPA 276
speed.
TTaabblle 1 e 1 ((ccoonnttiinnueuedd))
Tested Country Method Radiative effect Firebrands Wind effect Others
structural scenario scenario scenario
element
[34]
France CEN TS 1187 Exposure to a radiant Standard cribs To some extent, —
panel of (10-12,5) kW/ placed on roof using a blower;
(test 3)
m (includes slope surface for fire propa-
angle effect of the gation on roof
roof) during 30 min only, not for hot
gases.
[9]
Austral- AS 1530.8.1 4+1 scenarios: Burning debris No Specific to
[8]
ia AS 1530.8.2 simulated by wildland fires
—  Direct flame im-
standard wood exposure.
pingement, based on
cribs placed be-
interior fire exposure.
side the wall.
—  4 scenarios of
distant flame impinge-
ment: radiant panel
(or radiation produced
from furnace) at
exposures of (12,5, 19,
29 or 40) kW/m for
10 min.
Exterior Japan ISO 834-1 Yes No No Adapted for
walls long-duration
Fire resistance Based on interior fire
exposure sce-
Facades exposure
narios.
[26]
JIS A 1310 Main façade: No No —
1,8
...