ISO/TS 5658-1:2006

TECHNICAL ISO/TS
SPECIFICATION 5658-1
First edition
2006-10-01
Reaction to fire tests — Spread of
flame —
Part 1:
Guidance on flame spread
Essais de réaction au feu — Propagation du feu —
Partie 1: Lignes directrices sur la propagation de la flamme

Reference number
©
ISO 2006
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ii © ISO 2006 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Principles of flame spread . 1
3 Characteristics of flame-spread modes . 2
3.1 General. 2
3.2 Horizontal, facing upward. 3
3.3 Vertical or inclined. 4
3.4 Horizontal, facing downward. 6
4 History of surface spread of flame tests . 7
5 Small-scale tests. 9
5.1 Method given in ISO 5658-2 . 9
5.2 LIFT method . 10
5.3 Method given in ISO 9239-1 . 10
5.4 Method given in ISO 9239-2 . 12
6 Intermediate-scale tests. 12
6.1 Corner tests. 12
6.2 Method given in ISO 5658-4 . 12
6.3 Method given in ISO/TR 14696:1999 . 13
7 Large-scale tests. 14
7.1 Room corner test (ISO 9705) . 14
7.2 Room/corridor scenarios . 17
7.3 Façade scenarios. 20
7.4 Large-scale vertical flame-spread tests . 20
8 Flame spread within assemblies. 22
9 Flame spread by flaming droplets/particles . 24
9.1 Description of flame spread process with flaming droplets/particles . 24
9.2 Test methods to characterise flaming droplets/ particles. 24
9.3 Typical fire scenarios involving flaming droplets/ particles . 25
Bibliography . 26

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
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International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a
technical committee may decide to publish other types of normative document:
— an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
— an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting
a vote.
An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a
further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is
confirmed, it is reviewed again after a further three years, at which time it must either be transformed into an
International Standard or be withdrawn.
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.
ISO/TS 5658-1 was prepared by Technical Committee ISO/TC 92, Fire safety, Subcommittee SC 1, Fire
initiation and growth.
This first edition of ISO/TS 5658-1 cancels and replaces ISO/TR 5658-1:1997, which has been technically
revised.
ISO 5658 consists of the following parts, under the general title Reaction to fire tests — Spread of flames:
⎯ Part 1: Guidance on flame spread (Technical Specification)
⎯ Part 2: Lateral spread on building and transport products in vertical configuration
⎯ Part 4: Intermediate-scale test of vertical spread of flame with vertically oriented specimens
iv © ISO 2006 – All rights reserved

Introduction
The rate and extent of flame spread are important properties to be characterized when evaluating the reaction
to fire hazards of products that can be used in diverse applications such as in buildings, transport, furniture,
electrical enclosures, etc. Historically, there have been many approaches taken to the measurement of flame
spread and most of these have evolved with little fundamental justification. This Technical Specification
describes different modes of flame spread and proposes some theoretical principles to assist with the relevant
application of the data obtained from flame spread tests.
This guidance document is about flame spread and as such it fits within the scope of ISO/TC 92/SC 1. Flames
are a major cause of fires being initiated (usually described as ignitability) and fire growth (usually physically
observed as flames spreading from the initial seat of the fire where the ignition source was applied). Also,
within the scope of ISO/TC 92/SC 1, it is generally assumed that fire growth applies up to the point of a
developed fire after which the fire can spread (for example) from one compartment to another. This concept is
usually covered by the scope of ISO/TC 92/SC 2 (fire containment).
Many flame-spread tests measure the rate and extent of the flame front as the flame moves over the surface
of a large area, flat products such as linings on walls, ceilings and floors. Usually the orientation of the test
specimen is related to the end-use application (for example, exposed face upwards for floor-coverings). This
requirement for end-use relevance is satisfied by ISO 5658-2 and ISO 5658-4 when wall linings are evaluated.
Flame spread over construction and transport products is related to the fire scenario. ISO/TC 92/SC 1 have
initially concentrated on the development of tests to simulate flame spread in rooms and along corridors.
Other important scenarios where flame spread data are required are façades (both front and behind), shafts,
stairs and roofs; much of the theoretical guidance given in this Technical Specification can be applied to these
scenarios even though ISO test procedures might not be available as of the date of publication of this
Technical Specification.
Flame spread can also occur over non-planar products (e.g. pipes) and within assemblies (e.g. along joints or
inside air-gaps). Whilst this Technical Specification concentrates on the theory pertinent to flat products, some
of the theory outlined can be applied to improve the understanding of these more complex situations.
[1] [2]
The results of small-scale flame-spread tests (e.g. ISO 5658-2 and ISO 9239-1 ) and large-scale tests
[3]
(e.g. ISO 9705 ) can be used as components in a total hazard analysis of a specified fire scenario. The
theoretical basis of these tests is explained so that relevant conclusions or derivations can be made from the
test results.
TECHNICAL SPECIFICATION ISO/TS 5658-1:2006(E)

Reaction to fire tests — Spread of flame —
Part 1:
Guidance on flame spread
1 Scope
This Technical Specification provides guidance on flame spread tests. It describes the principles of flame
spread and classifies different flame-spread mechanisms.
2 Principles of flame spread
Flame-spread tests are designed to quantify the flaming process outside of the zone heated by the ignition
source (flaming, radiant or overheating) and as such, they help our understanding of how fire grows away
from the initial seat of the fire. This concept is relevant to flame spread within the compartment or cavity where
the fire originates (that is, the point/area of fire initiation/ignition). Flame-spread tests differ considerably in the
conditions that are specified for characterization of the flame-spread process. These conditions include the
following:
⎯ intensity and area of thermal attack of ignition source;
⎯ orientation of test specimen (for example, vertical, horizontal and inclined are normally defined);
⎯ ventilation in the vicinity of the test specimen;
⎯ mode of flame spread (see Table 1).
Flammability of surfaces is a major concern of many regulations. The primary room surfaces in buildings, for
example, are any combustible linings used on the walls or ceilings, along with floor coverings. Similar flame-
spread effects can also occur over the surfaces of transport vehicles (such as ships, trains, aircraft and buses).
To understand the role of bench-scale tests in assessing this hazard, the dominant fire effects shall be placed
in context.
The ceiling can show a very rapid fire spread and a high contribution to hazard. The least combustible
materials should generally be positioned on the ceiling in order to minimize fire hazard. There is not universal
[4]
agreement on this point and some studies conclude the opposite. For almost any fire scenario, flame
spread along the ceiling is wind-aided, which means that the air-flow and the flame spread are both in the
same direction.
For common fire scenarios, flame spread on walls is upward (wind-aided) in the vicinity of the fire source. In
other parts of the walls, the flame spread is downward (opposed-flow), since entrained air is moving upwards,
opposite to the direction of flame motion. Much of the wall can, however, be directly ignited by submersion into
the layer of hot gases forming below the ceiling. This ignition does not involve a flame-spread process at all,
but ceiling flammability directly accelerates it.
Generally, flame spread on floors within a room is very limited until later stages of a fire. Flame spread on
floors in corridors, however, can be of major concern. This flame spread is usually caused by a room fire
impinging on the adjacent corridor and igniting the flooring. There is usually some prevailing air-flow direction
within a corridor. Flame spread can then proceed either in the wind-aided direction, or as opposed flow.
Commonly, flame spread in both directions can occur simultaneously on corridor flooring materials.
In principle, two different bench-scale test methods would be required to represent the two fundamentally
different flame-spread processes of wind-aided spread and opposed-flow spread. The flame spread rates are
not similar in these two processes. Wind-aided spread tends to be much more rapid, since a large amount of
virgin combustible can be the flame tip, whereas in the opposite direction, the heating of the material is limited
to a very small heating zone. Research studies have shown, however, that a test solely dedicated to
[5]
examining wind-aided spread is not necessary .
Theory and experiments both reveal that wind-aided flame spread can often be directly predicted once the
heat release rate and the ignitability behaviour of the specimen is established. These would be done in bench-
[6] [7]
scale by the use of the ISO 5660 method for heat release rate and either ISO 5660-1 or ISO 5657 for
ignitability.
Flame spread for the opposed-flow configuration also requires information about the flame flux and the flame
[8]
heating distance for that geometry . In the context of ISO bench-scale test methods, this is the role for the
tests described in this part of ISO 5658 and in ISO 5658-2. Thus, while there are two flame-spread modes of
concern and while the wind-aided spread is often of dominant concern, there is a need only for two bench-
scale flame-spread ISO tests (ISO 5658-2 and ISO 9239-1). These tests are devoted solely to the opposed-
flow mode.
3 Characteristics of flame-spread modes
3.1 General
The characteristics of different flame-spread modes are described and summarized in Table 1. For each of the
modes, the dominant heat-transfer mechanisms are identified. The various modes are distinguished by two
criteria: orientation of the fuel surface and direction of the main flow of gases relative to that of flame spread.
Only flat fuel surfaces are considered. It is assumed that the fuel slab is located in a normal gravity
environment, i.e. special cases such as flame spread under microgravity conditions (spaceships) are not
considered. The analysis is for thick fuels, or else thin fuels in combination with a backing board. Cases where
burning can be on two sides simultaneously (e.g. upward flame spread over curtains) are not explicitly
included as a specific flame-spread mode. In addition, discontinuous flame spread caused by separation of
flaming parts from the pyrolyzing region of a fuel slab is not included in this clause. This effect can occur with
some products in modes B.a, B.b, B.c and C.a. Flame spread from flaming droplets/particles is further
described in Clause 9.
Table 1 — Modes of flame spread
Mode reference Application Type of flame spread
A.a Flooring; Horizontal Opposed-flow
A.b Flooring; Horizontal Opposed-flow
A.c Flooring; Horizontal Wind-aided
B.a Walls; Vertical Wind-aided
B.b Walls; Vertical Opposed-flow
B.c Walls; Vertical Opposed-flow
C.a Ceilings; Horizontal Wind-aided
2 © ISO 2006 – All rights reserved

3.2 Horizontal, facing upward
a) Mode A.a. Flame spread over a horizontal surface away from a burning area is illustrated in Figure 1. The
burning area has the characteristics of a pool fire. The flow rate of air entrained into the flame is assumed
to be reasonably uniform around the perimeter of the fire. Flame spread is against the direction of the
entrained air flow and is, therefore, of the opposed-flow type. The heat transfer to the non-burning fuel is
primarily flame radiation. Gas-phase conduction between the flame foot and the virgin fuel is the
dominant mode of heat transfer; it occurs only locally, close to the pyrolysis front. If the flow rate of air
entrainment is not uniform around the perimeter, the flame tilts in the direction of the dominant flow. As a
result, the relationship of the far field flame radiation to the unburnt fuel is no longer symmetrical. Objects
blocking the flow and ventilation openings providing fresh air can have a pronounced effect on the flow
field close to the fire.
Key
1 flame height
2 air flow
3 spread (mode A.a)
4 pyrolyzing region
NOTE See 3.2 a).
Figure 1 — Flame spread, mode A.a
b) Mode A.b is identical to A.a in 3.2 a), except that there is now a forced air flow that tilts the flame over in
the direction of the flow. This is illustrated in Figure 2. On the upstream side of the pool fire, flames
spread against the air flow. However, the view factor between the flame and the non-burning fuel on this
side is now very small. Consequently, the far field flame radiation becomes negligible and the gas-phase
conduction near the pyrolysis front is the only dominant method of heat transfer. In fact, significant flame
heating is over only a very small region near the pyrolysis front (a few millimetres). Therefore, the spread
rate is very slow and opposed-flow flame spread is commonly referred to as creeping spread.
c) Mode A.c is illustrated at the downstream side of the flame in Figure 2. Flames cover the fuel area
between the pyrolysis front and the flame tip. The heat transfer to this area is primarily by flame radiation
and convection. This is a typical example of wind-aided flame spread. There is still gas-phase heat
conduction near the pyrolysis front, but this mechanism is rather insignificant. Due to the increased view
factor, flame radiation in the region between the pyrolysis front and the flame tip is much greater than in
mode A.a, at least when flames are luminous.
Key
1 air flow
2 spread (mode A.b)
3 spread (mode A.c)
4 pyrolyzing region
NOTE See 3.2 b) and 3.2 c).
Figure 2 — Flame-spread modes A.b and A.c
3.3 Vertical or inclined
a) Mode B.a. Perhaps the most important flame-spread mechanism is that of upward spread over vertical
surfaces. This mode, B.a, is illustrated in Figure 3 and is very similar to that of mode A.c. The main
difference is that flames cover part of the non-burning fuel ahead of the pyrolysis front due to buoyancy.
Wind-aided spread is important because it is by far the fastest flame-spread mechanism. Consequently,
many bench- and intermediate-scale tests used for regulatory purposes evaluate the wind-aided flame-
spread potential of a material as a measure of its hazard in fire, for example the ASTM E84 Tunnel
[9] [10]
Test and the DIN 4102 test.
b) Mode B.b. Downward spread from a wall flame, is also shown in Figure 3. It is a form of opposed flow or
creeping spread analogous to mode A.b.
c) Mode B.c. Lateral spread, is illustrated in Figure 4. Heat transfer to the non-burning fuel is primarily
through gas-phase conduction near the pyrolysis front. Consequently, this mode is similar to that of A.b
and B.b.
d) The important flame-spread mechanisms over an inclined plane are dependent upon the angle of
inclination of a surface and the extent of the pyrolyzing region in relation to the width of the combustible
surface. For surfaces inclined at angles in excess of around 30°, flame spread can be represented as
illustrated in Figure 5. The flames from the burning fuel are in contact with the fuel surface ahead of the
pyrolyzing region, producing substantial radiative and convective heat transfer to the fuel. The substantial
flame lean is due to the fluid dynamics of the air entrainment process and results in a mode of flame
spread similar to that of upward spread over vertical surfaces, as shown in Figure 3. This flame-spread
[11]
process is evaluated in the NT Fire 007 test . This effect is also described in 7.2.5 in relation to sloping
corridors. For angles of inclination up to 30°, the modes of flame spread are represented by combinations
of Figures 1 (mode A.a) and 2 (mode A.c).
4 © ISO 2006 – All rights reserved

Key
1 upward spread (mode B.a) (wind-aided)
2 downward spread (mode B.b) (opposed flow)
3 pyrolyzing region
NOTE See 3.3 a) and 3.3 b).
Figure 3 — Flame-spread modes B.a and B.b

Key
1 air flow
2 lateral spread (mode B.c)
3 wall
4 floor
NOTE See 3.3 c).
Figure 4 — Flame-spread mode B.c
Key
1 pyrolyzing region
2 spread
a
θ W 30°.
Figure 5 — Flame spread up an inclined plane
3.4 Horizontal, facing downward
An example of ceiling spread, mode C.a, is shown in Figure 6. The mechanism for ceiling spread may be
applied to the underside of wide ventilation ducts. Buoyancy and the main flow of gases result in a wind-aided
type of spread similar to A.c and B.a.

Key
1 ceiling spread (mode C.a)
2 main flow of gases
NOTE See 3.4.
Figure 6 — Flame spread, mode C.a
6 © ISO 2006 – All rights reserved

4 History of surface spread of flame tests
Different spread of flame tests have been developed in several countries and for different applications.
Tables 2 and 3 provide parameters for ten commonly used spread of flame tests.
NOTE The difference between the tests concerns specimen size, specimen orientation (sometimes depending on the
type of application for which a material is designed), heat and ignition source applied to the specimen, as well as criteria
for acceptance.
8 © ISO 2006 – All rights reserved

Table 2 — National spread-of-flame tests based on radiant heat ignition models
Test Specimen orientation Direction of Specimen Heat flux Pilot ignition source Criteria Principal
flame spread size at hot end of countries of use
mm specimen
kW/m
[63]
ASTM E162 Inclined (face down) Downward 150 × 460 30 Horizontal gas flame, applied Flame spread, heat evolved, smoke USA
to upper end
[62]
ASTM E648 Horizontal (face up) Horizontal 250 × 1 050 11 Horizontal gas flame, applied Critical flux for spread USA, Germany
to the hot end
[13]
BS 476-7 Vertical Lateral 885 × 265 33 Vertical gas flame, applied to Extent and velocity of spread after GB, Belgium
the hot end 1,5 min and 10 min
[64]
NEN 3883 Vertical Lateral 1 000 × 230 37 Vertical gas flame, applied to Flame spread after 1,5 min and Netherlands
the hot end 10 min
[65]
UNI 9174 Vertical (wall position) Lateral 800 × 155 30 Gas flame, applied to the hot Velocity and extent of spread Italy
Horizontal (floor position) Horizontal 12 end Critical flux for spread of flame
Horizontal (ceiling position) Horizontal 16
[66]
NFP 92-506 Vertical Lateral 400 × 95 30 Vertical gas flame, applied to Extent of flame spread at 1 min and France
the hot end 10 min
IMO Resolution Vertical Lateral 155 × 800 50 Vertical gas flame, applied to Heat for sustained burning (Q ) For ships in
sb
[12]
A 653 (16) the hot end Critical flux at extinguishment (CFE) different
[67]
ASTM E1317-90 countries
USA
Table 3 — National spread-of-flame tests based on flame ignition models
Test Specimen orientation Direction of Specimen Heat flux Pilot ignition source Criteria Principal
flame spread size at hot end of countries of use
mm specimen
kW/m
[10]
DIN 4102 Vertical (four opposed Vertical 190 × 1 000 30 + influence Gas flame at lower end of Flame spread after 10 min Germany
specimens) of opposite specimen (pilot and radiation)
burning material
[9]
ASTM E84 05-01 Horizontal Horizontal 510 × 7 320 35 Horizontal gas flame, applied Flame spread smoke USA, Canada
(face down) to one end of specimen, with
heat output of 5,3 MJ/min
[44]
NT Fire 002 Vertical Vertical 800 × 300 35 Gas flame, applied to lower Ignitability Scandinavia
end of specimen Flame spread Austria

5 Small-scale tests
5.1 Method given in ISO 5658-2
NOTE See Reference [1].
ISO 5658-2 applies to a surface spread of flame test where the test specimen is exposed to a heat flux of
2 [12]
50 kW/m . The test was developed by the International Maritime Organization (IMO) .
The purpose of the test method is to provide a method of classifying surface finish materials used on-board
ships on the basis of their characteristics of surface flame spread.
The development concentrated on lateral flame spread over a vertical orientated specimen, because
a) an ISO spread-of-flame test utilized lateral flame spread;
[13]
b) reference was made to British Standard BS 476-7 ;
c) heat-release measurement on the IMO test method is only possible with the specimen in a vertical
position.
During the first stage of the round-robin test in IMO, some laboratories found it difficult to obtain a strictly
specified heating condition because of the variety of the fuel (methane, propane, electric, etc.).
However, it was also found that if test results were described as multiplication of flame spread time at a place
on the specimen and irradiance at this position, the results showed a good agreement among laboratories,
even if there were some variance in the ability of laboratories to obtain identical heating gradients.
Due to the above reason, this parameter was introduced for classifying materials. The level of the
classification on flame spread was developed in conjunction with BS 476-7.
“Heat for sustained burning (Q )” and “Critical irradiance at extinguishment (CFE)” are used in the IMO
sb
spread of flame test as parameters to describe degree of lateral flame spread on the surface of materials. The
decision on the use of these parameters was a consequence of experimental studies on the test method and
a consideration of the parameters of a similar test method (BS 476-7).
BS 476-7 specifies the heating condition of the specimen by incident heat flux. Then, flame spread distance at
1,5 min from the beginning of the test and maximum flame-spread distance within 10 min are used for
categorizing the specimen in one of the four classes. During the discussion in IMO, it was assumed that
incident heat flux along the lateral direction of the specimen is a more direct explanation of the heating
condition than lateral distance, and that incident irradiance at the maximum flame-spread position (CFE) can
be used instead of maximum flame-spread distance as a parameter that indicates the capability of the flame
spread.
In IMO, it is assumed that flame spread at 1,5 min is an expression of the flame-spread speed and that
multiplication of incident heat flux and time of flame spread to the position (Q ) can be used as a parameter
sb
of flame-spread speed. Some experimental studies have indicated that even if the heat flux condition is
different, in some limited degree almost the same CFE and Q could be obtained.
sb
Results of some experimental studies and first round-robin tests on the test method have demonstrated that a
logarithm plot of the flame-spread time to positions along the specimen against incident heat flux on these
[14]
positions gives a unique linear line for the specimen, and the slope is nearly – 1 (see Figure 7). This
means that multiplication of incident heat flux and flame-spread time can be a unique value for a material.
[15],[16]
Taking into account a comparison test of the results of BS 476-7 and the IMO spread-of-flame test ,
pass/fail criteria for the IMO test were developed using CFE and Q .
sb
5.2 LIFT method
The LIFT procedure for determining ignition and lateral flame spread was standardized in the U.S.A. as
[17]
ASTM E1321-90 and has been used for some research and modelling purposes.
This fire-test response standard determines material properties related to piloted ignition of a vertically
oriented specimen under a constant and uniform heat flux and to lateral flame spread on a vertical surface
due to an externally applied radiant-heat flux.
The results of this test method provide a minimum surface flux and temperature necessary for ignition and for
lateral spread, an effective material thermal inertia value, and a flame-heating parameter pertinent to lateral
flame spread.
The results of this test method can be used to predict the time to ignition and the velocity of lateral flame
spread on a vertical surface under a specified external flux. This analysis can be done using the equations in,

for example, References [17], [18] that govern the ignition and flame-spread processes and which have been
used to correlate the data.
[19]
The analysis may be used to rank material performance by some set of criteria applied to the correlation,
or the analysis may be employed in fire growth models to develop a more rational and complete hazard
assessment for wall materials.
5.3 Method given in ISO 9239-1
NOTE 1 See Reference [2].
This project leading to the publication of ISO 9239-1:1997 was initiated by ISO/TC 38/SC 19, Burning
behaviour of textiles and textile products, and had progressed to the development of a draft by 1988. In 1992,
ISO/TC 92/SC 1 conducted a ballot for a new work item on flame spread over all types of floor coverings. This
work item was well supported and the development of flame-spread tests for floor coverings (see
References [52], [55], [58], [59], [60]), including both textiles and non-textiles and taking into account the latest
[20]
improvement described in ASTM E648, was begun by ISO/TC 92/SC 1 in 1993. ISO 9239-1:1997 was
published in 1997. Subsequent to this publication, the European Commission decided that this method should
be used to classify floorings in support of the Construction Products Directive. Further work was initiated
according to the Vienna Agreement in CEN/TC 127 Fire safety in buildings in cooperation with
ISO/TC 92/SC 1. The precision of the method was further examined by a European inter-laboratory trial
involving 13 laboratories and 10 floorings. A revised second edition was published as ISO 9239-1:2002.
NOTE 2 A harmonized version, EN/ISO 9239-1:2000, was also published for regulatory use in Europe.
ISO 9239-1 provides a simple method by which the horizontal surface spread of flame on a horizontal
specimen can be determined for comparative purposes. This method is particularly useful for research,
development and quality control purposes.
ISO 9239-1 describes a test method for measuring the wind-opposed flame-spread behaviour (mode A.a) of
horizontally mounted floor covering systems exposed to a radiant heat gradient in a test chamber when ignited
with a pilot flame. The imposed radiant flux simulates the thermal radiation levels likely to impinge on the floor
of a corridor whose upper surfaces are heated by flames or hot gases or both, during the early stages of a
developing fire in an adjacent room or compartment under wind-opposed flame-spread conditions.
This test method is applicable to all types of floor coverings such as textile carpets, cork, wood, rubber and
plastic coverings.
The test is intended for regulatory purposes, specifications or development and research.
This test method consists of mounting conditioned specimens in a well-defined field of radiant heat flux from
2 2
11 kW/m to 1 kW/m and measuring the rate of spread of flame and the position of flame extinguishment.
10 © ISO 2006 – All rights reserved

A test specimen (1 050 mm long by 230 mm wide) is placed in a horizontal position below a gas-fired radiant
panel inclined at 30° and a pilot flame is applied to the hotter end of the specimen.
Following ignition, any flame front that develops is noted and a record is made of the progression of the flame
front horizontally along the length of the specimen in terms of the time it takes to travel to various distances.
The results are expressed in terms of flame-spread distance versus time and their derived radiant fluxes at X
minutes (HF-X) as well as the critical heat flux at extinguishment (CHF). Since the average heat for sustained
burning (Q ) is not required by European regulations, this parameter, which was included in ISO 9239-1:1997,
sb
was deleted from the revised second edition ISO 9239-1:2002.
The test may be terminated after 30 min since burning behaviour may not be significant for fire hazard
assessment purposes after this point in time.

Key
X incident heat flux, expressed in kW/m
Y flame-spread time, expressed in seconds
hard-wood fibre board
soft-wood fibreboard
melamine-formaldehyde laminate

acrylic carpet
wool carpet
Figure 7 — Relationship between heat flux and flame-spread time in ISO 5658-2 and IMO tests
5.4 Method given in ISO 9239-2
NOTE See Reference [21].
[21]
ISO 9239-2 was developed in recognition that more severe fire conditions on floorings than those
[22]
represented by ISO 9239-1 are found in post-flashover scenarios . The fire model for ISO 9239-1 is for
wind-opposed flame-spread behaviour (mode A.a). Research conducted after the introduction of
ISO 9239-1:2002 shows that heat fluxes higher than 11 kW/m can be imposed on floorings inside
[23], [24], [25]
compartments containing a fully developed fire (that is, post-flashover situations) . In addition,
wind-aided conditions (mode A.c) can occur in corridors, on sloping floors and up stairs. Under these mode-
A.c wind-aided conditions with developed fires, heat fluxes onto the floor of 25 kW/m are recorded.
The apparatus for ISO 9239-2 is essentially similar to that for ISO 9239-1:2002. Apart from the increase in gas
supply to the radiant panel that is required to obtain 25 kW/m at the hot end of the test specimen, the only

other change is to modify the air flow over the test specimen. In ISO 9239-2, the specimen holder has been
redesigned so that the air enters the test chamber at the hotter end of the exposed specimen. The air velocity
in the exhaust stack in ISO 9239-2 is 2,5 m/s, which is the same as in ISO 9239-1:2002.
The precision of ISO 9239-2 has been determined in a round-robin in which seven laboratories participated.
The results of this round-robin confirm that the variability obtained in ISO 9239-2 is similar to that obtained in
ISO 9239-1:2002. In the analysis of the CHF parameter, coefficients of variation of 6 % to 18 % (repeatability)
and 10 % to 30 % (reproducibility) were found for most flooring.
6 Intermediate-scale tests
6.1 Corner tests
A full-scale corner test is a widely recognized configuration for conducting large-scale fire test evaluations for
demonstrating the flame-spread potential and the material damage characteristics of insulated walls and
ceilings. A corner provides a critical surface geometry for evaluating the fire behaviour of material surfaces
since it results in a combined heat flux from the conductive, convective and radiative response of any material
burning in the corner. Large-scale corner tests are, however, expensive to conduct. A scaled-down screening
test that exhibits good reproducibility and good correlation is therefore useful for predicting the results of full-
scale corner testing. A variety of small corner tests have been judged to meet these criteria and the EN 13823
[26]
single-burning item (SBI) test is now used in Europe for regulatory purposes. The SBI test offers the
possibility to measure lateral flame spread but in practice lateral flame spread rarely travels further than 0,6 m
on the long wing due to the lack of a ceiling and high ventilation through the test specimen assembly.
Corner tests are particularly useful for measuring wind-aided flame spread on the tops of the walls and over
the ceiling (mode C.a). They are also able to show opposed-flow flame spread (mode B.c) laterally and
downwards over the walls for more flammable linings.
6.2 Method given in ISO 5658-4
NOTE See Reference [27].
ISO 5658-4 specifies an intermediate-scale method of test for measuring the vertical spread of flame over a
1,5 m × 1,0 m specimen of a product orientated in the vertical position. A measure of lateral spread can also
be obtained. The test provides data suitable for comparing the performance of materials, composites or
assemblies that are used as the exposed surfaces of walls or other vertically orientated products in
construction and transport applications. Some products with profiled surfaces can also be tested with a
modified procedure representative of the end-use conditions of the product.
The modes of flame spread measurable in this method are:
⎯ vertical upward: mode B.a;
12 © ISO 2006 – All rights reserved

⎯ vertical downward mode B.b;
⎯ lateral mode B.c.
Upward flame spread is not limited to surfaces that are vertical. It is recognized that an enhanced form of
upward, wind-aided flame spread can also occur on surfaces at an angle greater than 20° from the horizontal
without any external ventilation. This type of flame spread can occur in both planar sloping surfaces and
stepped surfaces such as stairs. Flame spread in these situations can become very rapid and can cause
serious problems in escape routes such as stairs and escalators. When assessing stepped or sloping surface
materials, it can be more appropriate to use a vertical flame spread test rather than a test in which the
specimen is horizontal.
ISO 5658-4 is applicable to the measurement and description of the properties of materials, products,
composites or assemblies in response to radiative heat in the presence of non-impinging pilot flames under
controlled laboratory conditions. The heat source can be considered to represent one burning item such as a
wastepaper bin or an upholstered chair within an enclosure, and this scenario is generally considered to apply
[28] [29]
during the early developing stage of a fire (see ISO/TR 11696-1 and ISO/TR 11696-2 ).
The test method consists of exposing conditioned vertically orientated specimens to a single well-defined field
2 2
of radiant heat flux, which is typically up to 35 kW/m to 45 kW/m near the base of the specimen.
Measurements are made of the time of ignition, of the vertical spread of flame and, where appropriate, of
observations of other fire-spread effects, such as flaming droplets/particles and lateral spread.
A test specimen is placed in a vertical position adjacent to a gas-fired radiant panel that exposes the lower
part to a defined field of radiant heat flux. A non-impinging line pilot burner is positioned above the radiated
area of the specimen to ignite volatile gases issuing from the surface.
Following ignition, any flame front that develops is noted and a record is made of the progression of the flame
front vertically over the height of the specimen in terms of the time it takes to travel various distances. The
results are expressed in terms of ignition time and flame-spread distance versus time.
Mass loss, heat release and smoke data can also be measured if required. For these measurements, the
[3]
apparatus should be positioned underneath a calibrated hood/duct facility; for example, see ISO 9705 .
A number of flame-spread characteristics may also optionally be derived from the measurements taken in
ISO 5658-4. Average flame-spread rates (both vertically and laterally) can be calculated based on flame-
spread distances measured from the X-O and Y-O reference lines drawn on the test specimens.
The precision of ISO 5658-4 has been determined in a large inter-laboratory trial involving 11 laboratories and
16 products. Flame-spread results were recorded using specific software that allowed flame spread to be
measured into 100 mm by 100 mm zones drawn as a grid over the whole test specimen. The area of flame
spread gave coefficients of variation of 0 % to 36 % (repeatability) and 0 % to 61 % (reproducibility), which
compare favourably with values found in other inter-laboratory trials on other reaction-to-fire parameters.
6.3 Method given in ISO/TR 14696:1999
NOTE See Reference [30].
[61]
In ISO/TR 14696:1999 , Annex F, it is stated, “The ICAL is used to determine many of the parameters or
values needed in computer fire models”. Flame spread is not included in the examples described since no
references were available at the time of the publication of ISO/TR 14696. However, the ASTM E-1623 ICAL
standard indicates in the scope that “this test method is suitable for determining the flame spread constant but
does not provide the testing and calculating procedures due to insufficient testing and research”.
Since the preparation of both the ISO and ASTM ICAL documents, a significant amount of flame-spread work
[31]
has been performed using th
...