ISO/TR 5658-1:1997

TECHNICAL
ISO/TR
REPORT
5658-l
First edition
1997-12-15
Reaction to fire tests - Spread of flame -
Part 1:
Guidance on flame spread
Essais de &action au feu - Propagation du feu -
Partie I: Guide sur Ia propagation de la flamme
Reference number
ISOTTR 5658-l : 1997(E)

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ISO/rR 5658-l :1997(E)
Page
Contents
1
1 Scope
1
2 Principles of flame spread
2
3 Characteristics of flame spread modes
7
4 History of surface spread of flame tests
9
5 Small-scale tests
13
6 Intermediate-scale tests
13
7 Large-scale tests
24
8 Flame spread within assemblies of building products
27
Annex A Bibliography
0 IS0 1997
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ii

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ISO/TR 5658-l : 1997(E)
@ IS0
Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0
member bodies). The work of preparing International Standards is normally carried out through IS0 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. IS0 collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
The mai n task of technical committees is to prepare International Standards, but in exceptional ci rc urnstances a
following types:
technica I committee may propose the pu blication of a Technical Report of one of the
of an International Standard, despite
- type 1, when the required support cannot be obtained for the publication
repeated efforts;
when the subject is still under technical development or where for any other reason there is the future
- type 2,
nal Standard;
but not immediate possibility of an agreement on an lnternatio
- type 3, when a technical committee has collected data of a different kind from that which is normally published
as an International Standard (“state of the art”, for example)
Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide whether they
can be transformed into International Standards. Technical Reports of type 3 do not necessarily have to be
reviewed until the data they provide are considered to be no longer valid or useful.
BSOJV-R 5658-l 7 which is a Technical Report of type 3, was prepared by Technical Committee lSO/TC 92, fire
safety, Subcommittee SC 1, Reaction to fire.
IS0 5658 consists of the following parts, under the general title Reaction to fire tests - Spread of flame:
- Part I: Guidance on flame spread (Technical Report)
- Part 2: Lateral spread on building products in vertical configuration
- Parf 3: Lateral ignition of and flame spread on building products in vertical configuration (LIFT) method (Technical
Report)
- Par? 4: Intermediate-scale spread of flame with verfically oriented specimens
Annex A of this Technical Report is for information only.

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ISO/TR 5658-l :1997(E)
Introduction
The rate and extent of flame spread are important properties to be characterized when
evaluating the reaction-to-fire hazards of construction products. 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 Report 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.
Many flame spread tests measure the rate and extent of the flame front as the flame moves
over the surface of 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 IS0 5658-2 and ISO/TR 5658-3 when wall-linings are to be evaluated.
Flame spread over construction products is related to the fire scenario. ISO/TC 92/SC 1 have
concentrated on development of tests to simulate flame spread in rooms and along corridors.
Other important scenarios where flame spread data are required are facades (both front and
behind), shafts, stairs and roofs; much of the theoretical guidance given in this Technical
Report may be applied to these scenarios even though IS0 test procedures may not yet be
available.
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 Report concentrates on the theory
pertinent to flat products, some of the theory outlined may be applied to improve the
flame spread within
understanding of these more complex situations (see clause 8
9
assemblies).
Flame spread initiated by removal of flaming drops or debris is not treated in this Technical
Report. Empirically derived tests for these secondary flame spread phenomena are available
(see ref. [34]).
NOTE - Flame spread can be reduced and sometimes eliminated due to melting and
dripping; these effects are also not treated in this Technical Report.
iv

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TECHNICAL REPORT @ IS0
ISO/TR 5658-l : 1997(E)
Reaction to fire tests - Spread of flame -
Part 1:
Guidance on flame spread
1
Scope
This Technical Report provides guidance on flame spread tests for construction products. It
describes the principles of flame spread and classifies different flame spread mechanisms.
The results of small-scale flame spread tests (e.g. IS0 5658-2 [31], ISO/TR 5658-3 [32] and
IS0 9239-l [35]) and large-scale tests (e.g. IS0 9705 [ 131) may 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 may be made from the test results.
2 Principles of flame spread
Flammability of room surfaces is a major concern of all building regulations. The primary
room surfaces in question are any combustible linings used on the walls or ceilings, along
with floor coverings. To understand the role of bench-scale tests in assessing this hazard, the
dominant fire effects must be placed in context.
The ceiling can show a very rapid fire spread and a high contribution to hazard. Recent
research suggests that the least combustible materials should be allocated to the ceiling in
order to minimize fire hazard. There is not universal agreement on this point, however, and
some studies conclude the opposite (see reference [25]). For almost any fire scenario, flame
spread along the ceiling is wind-aided, that is, the air-flow and the flame spread are both in
the same direction.
For common fire scenarios, flame spread on walls will be upward, that is wind-aided, in the
vicinity of the fire source. In other parts of the walls, flame spread will be downward, that is
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 it is directly accelerated by ceiling flammability.
Flame spread on floors is generally ignorable within a room since it is very limited until quite
late in 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 will usually be 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.

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ISO/rR 5658-l : 1997(E)
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 examining wind-
aided spread is not necessary [26].
Theory and experiments both reveal that wind-aided flame spread can be directly predicted
once the heat release rate and the ignitability behaviour of the specimen is established. These
would be done in bench-scale by the use of the IS0 5660 method for heat release rate and
either IS0 5660 or IS0 5657 for ignitability.
Flame spread for the opposed-flow configuration also requires information about the flame
flux and the flame heating distance for that geometry [27] In the context of IS0 bench-scale
test methods, this is the role for the IS0 5658 test. Thus, while there are two flame spread
modes of concern and while the wind-aided spread is often of dominant concern, there is seen
to be a need only for one lateral bench-scale flame spread IS0 test, and this test is devoted
solely to the opposed-flow mode.
3 Characteristics of flame spread modes
3.1 General
In this clause, the characteristics of different flame spread modes are described and
summarized in Table 1. For each of the modes, 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 furthermore 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 may be on two sides simultaneously
(e.g. upward flame spread over curtains) are not explicitly included.
1. Flame height
2. Air flow
3. Spread (A.a)
4. Pyrolyzing region
Figure 1 - Flame spread mode A.a (3.1 (a))

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ISO/TR 56584 : 1997(E)
Table 1 - Modes of flame spread
Mode reference Application Type of flame spread
*
3.2 Horizontal facing upward
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 air flow rate 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. Only locally, close to the
pyrolysis front, is gas phase conduction between the flame foot and the virgin fuel the
dominant mode of heat transfer. If the entrained air flow rate is not uniform around the
perimeter, the flame tilts in the direction of the dominant flow. As a result, the far field flame
radiation to the unburnt fuel is no longer symmetrical. Objects blocking the flow and
ventilation openings providing fresh air may have a pronounced effect on the flow field close
to the fire.
b) This configuration is identical to that in 3.1 a), except that there is now a forced air flow
because of which the flame tilts over in the direction of the flow. This mode 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 only over a very small region near the pyrolysis front (a few mm). Therefore, the
spread rate is very slow and opposed-flow flame spread is commonly referred to as creeping
spread. For many fuels the heat transfer is insufficient to maintain the spread, at least in
absence of external heating (such as in 3 l 1 a)= A criterion for creeping spread will be discussed
below.
1. Air flow
2. Spread (A.b)
3. Spread (A.c)
4. Pyrolyzing region
Figure 2 - Flame spread modes A.b and A.c (3.1 b and 3.1 c)

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@ IS0
ISOnR 5658-l :1997(E)
I. Upward spread @a)
(wind-aided)
2. Downward spread (B.b)
(opposed flow)
3. Pyrolyzing region
Figure 3 - Flame spread modes B.a and B.b (3.2 a and 3.2 b)

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@ IS0 ISO/TR 5658-l’: 1997(E)
1. Pyrolyzing region
2. Spread
030”
Figure 3a - Flame spread up an inclined plane
c) This mode is illustrated at the downstream side of the flame in figure 2. The fuel area
between the pyrolysis front and the flame tip is covered by flames. 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 3.1 a), at
least when flames are luminous.
3.3 Vertical or inclined
a) Perhaps the most important flame spread mechanism is that of upward spread over vertical
surfaces. This mode is illustrated in figure 3 and is very similar to that of 3. lc). 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 propensity of a material as a measure of its
hazard in fire, for example the ASTM E84 Tunnel Test [3] and the DIN 4102 [2] test.
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 3.1 b).
c) Lateral spread is illustrated in figure 4. Heat transfer to the non-burning fuel is primarily
gas phase conduction near the pyrolysis front. Consequently this mode is similar to that of
3.lb) and 3.2b).
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 pyrolysing region in relation to the
width of the combustible surface. For surfaces inclined at angles in excess of around 30 O,
flame spread can be represented as illustrated in figure 3a. The flames from the burning fuel
are in contact with the fuel surface ahead of the pyrolysing region, producing substantial
radiative and convective heat transfer to the fuel. The substantial flame lean is due to the fluid

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ISOmR 5658-l : 1997(E)
dynamics of the air entrainment process and results in a mode of flame spread similiar to that
of upward spread over vertical sufaces, as shown in figure 3. This flame spread process is
evaluated in the NT Fire 007 test [41]. This effect is also described in 7.2.5 in relation to
sloping corridors.For angles of inclination up to 30 O) the modes of flame spread are
represented by combinations of figures 1 (A.a.13. IL a) and 2 (A.c/3.1 c).
1. Air flow
2. Lateral spread (B.c)
Figure 4 - Flame spread mode B.c (4.2 c)
1. Ceiling spread (C.a)
2. Main flow of gases
Figure 5 - Flame spread mode C.a (3.3)

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lSO/TR 56584:1997(E)
3.4 Horizontal facing downward
Ceiling spread is shown in figure 5; a similar mechanism applies to the underside of wide
ventilation ducts. Buoyancy and the main flow of gases result in a wind-aided type of spread
similar to 3.1 c) and 3.2a).
4 History of surface spread of flame tests
Different spread of flame tests have been developed in several countries and for different
applications.
These tests are different concerning specimen size, specimen orientation (sometimes
depending from the type of application a material is designed for), heat and ignition source
applied to the specimen as well as criteria for acceptance.
Table 2 shows the most important “spread of flame tests” used all over the world.
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@ IS0
ISO/TR 5658~1:1997( E)
5 Small-scale tests
5.1 Method given in IS0 5658-2 [31]
IS0 5658-2 has been derived from a surface spread of flame test developed by the
International Maritime Organization (IMO): Recommendation on Fire Test Procedures for
Surface Flammability of Bulkhead, Deck and Ceiling Finish Materials: IMO Resolution
A.653(16) [9].
The purpose of the test method in IMO was to provide a method of classifying surface finish
materials used on board ships relating their characteristics of surface flame spread.
The development has concentrated on lateral flame spread over a vertical orientated
specimen, because:
a) there was a draft of an IS0 spread of flame test which utilized lateral flame spread;
b) reference was made to British Standard BS 476-7 [l];
c) heat release measurement on the IMO test method is only possible in a vertical
specimen position.
During the first stage of the round robin test in IMO, it was found difficult for some
laboratories 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 was 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 leve of
the classification on flame spread was developed in conjunction with BS 476-7.
‘Heat for sustained burning (HSB)’ and ‘Critical irradiance at extinguishment (CIE)’ are u led
in the IMO 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 consideration to 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 was a more direct explanation of the heating condition than lateral distance, and
that incident irradiance at the maximum flame spread position (CIE) could be used, instead of
maximum flame spread distance? as a parameter which indicated capability of flame spread.
In IMO, it is assumed that flame spread at 1,5 min was an explanation of the flame spread
speed, and that multiplication of incident heat flux and time of flame spread to the position
(HSB) can be used as a parameter of flame spread speed. Some experimental studies have
9

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lSO/TR 5658~1:1997( E)
@ IS0
indicated that even if the heat flux condition is different, in some limited degree almost the
same CIE and HSB could be obtained.
Results of some experimental studies and first round robin tests on the test method have
demonstrated that logarithm plotting of flame spread time to positions along the specimen
against incident heat flux on these positions gives a unique linear line for the specimen, and
the slope is nearly - 1; (see ref. [34], figure 6). This means that multiplication of incident heat
flux and flame spread time can be a material unique value.
Taking into account a comparison test, results between BS 476-7 and IMO spread of flame
test [29,3’7] pass/fail criteria for the IMO test were developed using CIE and HSB.
5.2 Method given in ISO/TR 5658-3 [32]
The continuing development of IS0 5658 is based on the LIFT procedure for determining
ignition and lateral flame spread, which has been standardized in U.S.A. as ASTM E1321-90
.
WI
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 [ 1 l] and [ 151, that govern the ignition
and flame-spread processes and which have been used to correlate the data.
The analysis may be used to rank material performance by some set of criteria [ 141 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.
10

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ISONR 5658-l :1997(E)
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1. Flame spread time (s) 6. Melamine formaldehyde
2. incident heat flux (kW/m2) laminate
3. Chip board 7. Acrylic carpet
4. tiard wood fiber board
8. Wool carpet
5. Soft wood fiber board
Figure 6 - Relationship between heat flux and flame spread time in IS0 5658-2 and
IMO tests
11

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lSO/TR 5658-l : 1997(E)
5.3 Method given in IS0 9239-1 [35]
This International Standard was initiated by ISO/TC 38&C 19, Textile Jloor coverings, and
was progressed to DIS in 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, including both textiles and
non-textiles and taking into account the last improvement described in ASTM E 648, was
begun by ISO/TC 92/SC 1 in 1993.
IS0 9239 provides a simple method by which 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.
This International Standard describes a method of test 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 11 kW/m2 to 1 kW/m2 and measuring the rate of spread of flame and
the position of flame extinguishment.
A test specimen (1050 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 which 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 (RF-X) as well as the critical heat flux at extinguishment (CRF)
and the average heat for sustained burning (HSB). The derivations for these last two
parameters are made by a similar procedure to IS0 5658-2.
The test may be terminated after 30 min since burning behaviour may not be significant for
fire hazard assessment purposes after this point of time.
12

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lSO/TR 5658-l :1997(E)
Further flame spread test developments are in progress to recognise the following additional
requirements of fire growth involving floor coverings :
a) Ventilation controlled test conditions to simulate wind-aided flame spread (mode
. e
A c>
b) Higher irradiances to the floor covering specimen to simulate the heat flux
conditions existing at floor level in developed fires; these conditions may require
exposing specimens to irradiances of 25 kW/m2.
6 Intermediate-scale tests
6.1 Corner tests
A full-scale corner test is a widely recognised 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
which 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 but none has yet been internationally standardized. In particular, specimen
assembly dimensions and testing times are convenient so that if necessary, several tests may
be conducted daily.
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 observe opposed-flow flame
spread (mode B.c) laterally and downwards over the walls for more flammable linings.
7 Large-scale tests
71 . Room/corner test (IS0 9705) (131
IS0 9705 describes a full-scale room fire test method to evaluate the performance of lining
materials in a room/corner scenario. The test room has a height and width of 2,44 m, and a
depth of 3,66 m. There is an open doorway of 0,76 m wide by 2,03 m high in the front wall.
All walls (except the front wall) and/or ceiling are lined with the test material. A gas burner
ignition source is placed in one of the rear corners of the compartment. The main
measurements are time to flashover, heat release rate and smoke obscuration in the exhaust
duct.
Corner fires are more severe than wall fires due to the radiative heat exchange between the
two burning walls. For this reason, corner tests have been preferred in the evaluation of pre-
flashover fire performance of wall linings. However, the physical phenomena controlling fire
growth in corner and wall scenarios are very similar, if not identical. Therefore, the
description of fire growth in a corner test given below is also applicable to wall fires. The
13

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lSO/rR 5658~1:1997( E)
important physical phenomena can be identified on the basis of visual observations of and
experience with full-scale tests. Fire size is primarily determined by the spread of flames
over the walls i.e. the increase in surface area of material involved:
a) At the start of a test, the ignition burner is lit. A diffusion flame develops and is in
contact with the walls. For burner sizes and power levels commonly used in
room/corner tests, the flame is turbulent. Figure 7 is a 3-D view of the room in this
corner test.
stage of a
1. Lateral spread
(opposed-flow)
2. Upward spread
(wind-aided)
Figure 7 - 3-D view of a corner fire in an early stage
b) The wall material in contact with the flame and plume is heated. The heat flux to
the wall is a function of location. It is the highest in the flame region, and decreases
sharply in the plume region. At a certain time, part of the material in contact with the
flame ig
...