ISO 5658-4:2001

INTERNATIONAL ISO
STANDARD 5658-4
First edition
2001-06-01
Reaction to fire tests — Spread of flame —
Part 4:
Intermediate-scale test of vertical spread of
flame with vertically oriented specimen
Essais de réaction au feu — Propagation du feu —
Partie 4: Essais à échelle intermédiaire de la propagation de la flamme
avec éprouvette orientée verticalement
Reference number
©
ISO 2001
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ii © ISO 2001 – All rights reserved

Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Normative references .1
3 Terms and definitions .2
4 Principle.3
5 Suitability of a product for testing .7
6 Test specimens.7
6.1 Exposed surface .7
6.2 Number and size of specimens.7
6.3 Construction of specimen assemblies.7
6.4 Conditioning.9
6.5 Reference lines .10
6.6 Storage of specimen assemblies.10
7 Test apparatus .12
8 Test enclosure.22
9 Setting-up and calibration procedure.22
9.1 Setting-up .22
9.2 Verification .23
9.3 Adjustment of the pilot flame .23
10 Test procedure.23
11 Derived flame spread characteristics (optional).26
11.1 General.26
11.2 Method 1 .26
11.3 Method 2a).26
11.4 Method 2b).26
11.5 Method 3 .27
12 Precision.27
13 Test report .27
Annex A (normative) Safety precautions.31
Annex B (normative) Specimen construction .32
Annex C (informative) Calibration of the working heat flux meter.33
Annex D (normative) Interpretation of results of this test procedure .34
Annex E (informative) Variability in the ignitability and flame spread measured in an
interlaboratory test .35
Bibliography.37
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
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.
Attention is drawn to the possibility that some of the elements of this part of ISO 5658 may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 5658-4 was prepared by Technical Committee ISO/TC 92, Fire safety, Subcommittee
SC 1, Fire initiation and growth.
ISO 5658 consists of the following parts, under the general title Reaction to fire tests — Spread of flame:
— Part 1: Guidance on flame spread (Technical Report)
— Part 2: Lateral spread on building products in vertical configuration
— Part 4: Intermediate-scale test of vertical spread of flame with vertically oriented specimen
Annexes A, B and D form a normative part of this part of ISO 5658. Annexes C and E are for information only.
iv © ISO 2001 – All rights reserved

Introduction
ISO/TR 5658-1 describes the development of standard tests for flame spread and explains the theory of flame
spread for various orientations.
ISO 5658-2 provides a simple method by which the lateral surface spread of flame on a vertical specimen can be
determined for comparative purposes. This method is particularly useful for research, development and quality
control purposes.
This part of ISO 5658 provides an intermediate-scale method by which the ignitability and vertical surface spread of
flame on a vertical specimen can be determined. The specimen is sufficiently large to obtain a measure of lateral
flame spread. Downward flame spread can also be examined as a wind-opposed spread on the specimen surface
or by the observation of any flaming drips.
Fire is a complex phenomenon; its behaviour and its effects depend upon a number of interrelated factors. The
behaviour of materials and products depends upon the characteristics of the fire, the method of use of the materials
and the environment in which they are exposed. The methodology of reaction-to-fire tests is explained in
ISO/TR 3814.
A test such as specified in this part of ISO 5658 deals only with a simple representation of a particular aspect of the
potential fire situation typified by a radiant heat source and flame; it cannot alone provide any direct guidance on
behaviour or safety in fire.
The attention of all users of the test is drawn to the warning given before clause 1.
INTERNATIONAL STANDARD ISO 5658-4:2001(E)
Reaction to fire tests — Spread of flame —
Part 4:
Intermediate-scale test of vertical spread of flame with vertically
oriented specimen
WARNING — So that suitable precautions can be taken to safeguard health, the attention of all concerned
in fire tests is drawn to the possibility that toxic or harmful gases may be evolved during exposure of test
specimens. The advice on safety given in annex A should also be noted.
1 Scope
1.1 This part of ISO 5658 specifies an intermediate-scale method of test for measuring the vertical spread
(upward and downward) of flame over a specimen of a product orientated in the vertical position. A measure of
lateral spread can also be obtained. It provides data suitable for comparing the performance of materials,
composites or assemblies, which are used as the exposed surfaces of walls or other vertically orientated products
in construction applications. Some products with profiled surfaces can also be tested with a modified procedure
representative of the end-use conditions of the product.
1.2 Upward flame spread is not limited to surfaces which 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 ways such as staircases. When assessing stepped or sloping surface materials, it may be more
appropriate to use a vertical flame spread test rather than a test in which the specimen is horizontal.
1.3 This part of ISO 5658 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 may be considered to represent a single burning item such
as a wastepaper bin or an upholstered chair within an enclosure, and this scenario would generally be considered
to apply during the early developing stage of a fire (see ISO/TR 11696-1 and ISO/TR 11696-2). This part of
ISO 5658 should not be used alone to describe or appraise the fire hazard or fire risk of materials, products,
composites or assemblies under actual fire conditions.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO 5658. For dated references, subsequent amendments to, or revisions of, any of these publications
do not apply. However, parties to agreements based on this part of ISO 5658 are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain
registers of currently valid International Standards.
ISO 554, Standard atmospheres for conditioning and/or testing — Specifications.
ISO/TR 11696-1, Uses of reaction to fire test results — Part 1: Application of test results to predict fire performance
of internal linings and other building products.
ISO/TR 11696-2, Uses of reaction to fire test results — Part 2: Fire hazard assessment of construction products.
ISO 13943, Fire safety — Vocabulary.
ISO/TR 14697, Fire tests — Guidance rules on the choice of substrates for building products.
3 Terms and definitions
For the purposes of this part of ISO 5658, the terms and definitions given in ISO 13943 apply, together with the
following.
3.1
assembly
fabrication of materials and/or composites, for example sandwich panels
NOTE The assembly may include an air gap (see 6.3.6).
3.2
backing board
board with the same dimensions as the specimen and used to back the specimen so as to represent end-use
conditions
NOTE See 7.10.
3.3
burned area
that part of the damaged area of a material which has been destroyed by either combustion or pyrolysis, under
specified test conditions
3.4
composite
combination of materials which are generally recognized in building construction as discrete entities
EXAMPLE Coated or laminated materials.
3.5
damaged area
total of the area of material affected by thermal phenomena under specified test conditions
NOTE See 10.11.
3.6
exposed surface
that surface of the specimen subjected to the heating conditions of the test
3.7
flame front
boundary of the combustion zone in the gaseous phase at the surface of a material
NOTE For vertical flames, the flame front is the tip of continuous flames, disregarding any detached transitory flame-
segments.
3.8
flashing
existence of flame on or over the surface of the specimen for periods of less than 1 s
3.9
irradiance
�at a point of a surface� quotient of the radiant heat flux incident on an infinitesimal element of surface containing
the point, and the area of that element
2 © ISO 2001 – All rights reserved

3.10
material
single substance or uniformly dispersed mixture
EXAMPLES Metal, stone, timber, concrete, mineral fibre, polymers.
3.11
product
material, composite or assembly about which information is required
3.12
radiantheatflux
power emitted, transferred or received in the form of radiation
3.13
specimen
representative piece of the product which is to be tested together with any substrate or treatment
NOTE The specimen may include an air gap. The specimen may also be tested as a stand-alone product without
substrates if this is representative of end-use conditions.
3.14
spread of flame
propagation of a flame front over the surface of a product under the influence of imposed irradiance and non-
impinging pilot flames
3.15
substrate
material which is used or is representative of that used, immediately beneath a surface product in end-use
EXAMPLE Skimmed plasterboard beneath a wall-covering.
3.16
sustained flaming
existence of flame on or over the surface of the specimen for periods of more than 4 s
3.17
transitory flaming
existence of flame on or over the surface of the specimen for periods of between 1 s and 4 s
3.18
lateral flame spread
progression of the flame front in a lateral direction over the specimen width
3.19
vertical flame spread
progress of the flame front in a vertical direction (upwards or downwards) over the specimen height
4Principle
4.1 The test method consists of exposing conditioned vertically-orientated specimens to a single well-defined
field of radiant heat flux (see Figure 1) and measuring the time of ignition, vertical spread of flame and, where
appropriate, observing other fire spread effects such as flaming drips or debris and lateral spread.
4.2 A test specimen is placed in a vertical position adjacent to a gas-fired radiant panel which 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 (see Figures 2 and 3).
4.3 Following ignition, any flame front which 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 to various distances.
4.4 The results are expressed in terms of ignition time and flame spread distance versus time.
Mass loss, heat release and smoke data may also be measured if required. For these measurements, the
apparatus should be positioned underneath a calibrated hood/duct facility; for example, see ISO 9705.
Figure 1 — Heat flux distribution on the calibration board
4 © ISO 2001 – All rights reserved

Key
1 Test specimen
2 Pilot flame burner
3 Vertical radiant panel at an angle of 35° to the specimen
4 Supply pipe
5 Direction of rotation of supply pipe
6 Debris collection tray
Figure 2 — Test apparatus
Dimensions in millimetres
Key
1 Exhaust hood 5 Debris collection tray
2 Exposed area of specimen 6 Floor level
3 Pilot flame burner 7 Specimen
4 Radiant panel
Figure 3 — Schematic of test apparatus
6 © ISO 2001 – All rights reserved

5 Suitability of a product for testing
A product having one of the following surface characteristics is suitable for evaluation by this method:
a) an essentially flat exposed surface;
b) a surface irregularity which is evenly distributed over the exposed surface provided that any cracks, fissures or
holes do not exceed 8 mm in width or 10 mm in depth and the total area of such cracks, fissures or holes at
the surface does not exceed 30 % of a representative area 155 mm square of the exposed surface;
c) products with profiled surfaces (e.g. ducting, panels, pipes) may also be tested in end-use conditions but it
should be recognized that flame spread rates and distances are then not directly comparable to those obtained
from essentially flat products.
6 Test specimens
6.1 Exposed surface
The product shall be tested on that face which will normally be exposed in practice, taking account of the following.
a) For asymmetric products where it is possible for either or both of the faces to be exposed in end-use, both
faces shall be tested.
b) If the face of the product contains a surface irregularity that is specifically directional (e.g. corrugations, grain
or machine-induced orientation which may, in practice, run horizontally or vertically), the product shall be
tested in both orientations.
c) If the exposed face contains distinct areas of different surface finish or texture, then the appropriate number of
specimens shall be provided for each distinct area of such finish or texture to be evaluated.
d) If the product is a pile carpet or other surface which is compressible by the flange of the pilot burner, a check
shall be made by presenting the specimen to the pilot burner without gas in the test position. If necessary, the
flange shall be adjusted so that the distance between the burner tube and the specimen is 25 mm.
6.2 Number and size of specimens
6.2.1 Three specimens shall be tested for each potentially exposed surface or orientation.
6.2.2 The specimens shall be (1 525 � 25) mm long by (1 025 � 25) mm wide by their end-use thickness. They
shall be representative of the product. The specimens may be constructed from a number of components suitably
jointed together. For specimens containing one or more vertical joints, one joint shall be placed at a distance of
250 mm from the left (or hot) edge of the exposed specimen. For specimens containing one or more horizontal
joints, one joint shall be placed at a distance of 350 mm from the lower edge of the exposed specimen.
6.2.3 The thickness of specimens of products with irregular surfaces (see 6.1) shall be measured from the
highest point of the surface. Products of normal thickness 300 mm or less shall be tested using their full thickness.
6.3 Construction of specimen assemblies
6.3.1 For thin materials or composites used in the fabrication of an assembly, the presence of an air gap and/or
the nature of any underlying construction can significantly affect the characteristics of the exposed surface. The
influence of the underlying layers should be understood and care taken to ensure that the test result obtained on
any assembly is relevant to its use in practice. Whenever possible, the specimen should be assembled in the
specimen holder (see 7.4). However, some specimens may be particularly bulky or heavy (e.g. brick wall
substrates). In these cases, the specimen may be assembled on the floor, with the exposed surface the usual
distance above the floor and the radiant panel presented to the specimen according to the principles shown in
Figure 3.
6.3.2 When the product is a surface coating, it shall be applied to the selected substrate (see annex B) using a
method and application rate recommended for its use.
6.3.3 When the product is a material or composite which would normally be attached to a substrate, then it shall
be tested in conjunction with the selected substrate (see annex B) using the recommended fixing technique (e.g.
bonded with the appropriate adhesive or mechanically fixed). The procedure for fixing the specimens to the
substrate shall be clearly stated in the test report [see clause 13 f)].
6.3.4 Where a product will normally be used without an air gap behind it, then after the conditioning procedures
specified in 6.4, place the specimen on a backing board and insert both in a specimen holder [see Figure 4a)].
6.3.5 Where a product will normally be used in its end use as a free-standing structural product (such as
partitioning, sandwich panels, glazing), insert the specimen alone into a specimen holder [See Figure 4b)].
6.3.6 Where a product will normally be used with an air gap behind it, after the conditioning procedures specified
in 6.4, place the specimen over conditioned spacers positioned around its perimeter and mount on a backing board
so that a (25 � 2) mm air gap is provided between the unexposed face of the specimen and the backing board.
Place the product on a backing board and insert both in a specimen holder (see Figure 5). Products containing air
gaps of <25 mm should preferably be tested under their end-use conditions.
A technique for mounting thin flexible materials is to staple the specimen closely to the backing board.
Key
1 Specimen holder 4 Specimen
2 Backing board 5 Overlap edge of specimen holder
3 Specimen (which may include a substrate) 6 Pushing frame
a) With backing board b) Without substrate or backing board
Figure 4 — Typical mounting of specimen
8 © ISO 2001 – All rights reserved

Key
1 Specimen holder 4 Backing board
2 Pushing frame 5 Specimen
3 Air gap 6 Spacer
Figure 5 — Typical mounting of specimen with backing board and spacers forming an air gap
6.4 Conditioning
6.4.1 All specimens shall be conditioned before test at a temperature of (23 � 2) °C and a relative humidity of
(50 � 5) %, according to one of the following options (see ISO 554).
1�
a) Conditioning for at least 4 days, until constant mass is achieved.
b) Conditioning for at least 3 weeks. Use of this option is not allowed for wood-based products, cement-based
products and gypsum-based products.
c) Conditioning for at least 4 weeks. The final mass and the relative mass difference of two successive weighing
operations, carried out (24 � 2) h and (2 � 2) h before the test shall be reported.
6.4.2 Backing boards and spacers (see 7.10) shall be dry and maintained for at least 2 days before use under
the same conditions as the test specimens (see 6.4.1).
The specimens shall be arranged within the conditioning environment such that air can circulate around each side
of each specimen.
1� Constant mass is considered to be attained when two successive weighing operations, carried out at an interval of 24 h, do
not differ by more than 0,1 % of the mass of the specimen.
6.4.3 The parts that compose a specimen (the product and the backing board on which it is fixed) shall be
conditioned separately or as a mounted specimen. Specimens that are glued to the backing board shall be glued
before conditioning.
6.4.4 The total test procedure (see clause 10) shall be carried out within 2 h after removal of the specimens from
the conditioned environment.
6.5 Reference lines
6.5.1 Mark two lines on the cut specimen to identify the lower and vertical edges of the specimen to be exposed
in the vicinity of the radiant panel [see Figure 6a)]. These lines should correspond to the specific overlap edge of
the specimen holder.
6.5.2 Mark two additional lines on the surface of the specimen to be exposed, as follows:
a) a horizontal line at 480 mm above the horizontal line drawn in 6.5.1; this will be referred to as the Y0 reference
line;
b) a vertical line at 200 mm from the vertical line drawn in 6.5.1; this will be referred to as the X0 reference line.
The intersection of the X0 and Y0 lines will be referred to as the zero point and this location shall be used to set up
software for the flame spread monitoring [see Figure 6b)].
6.5.3 Mark additional horizontal lines on the surface to be exposed at heights of 80 mm, 680 mm, 880 mm,
1 080 mm and 1 280 mm above the horizontal line drawn in 6.5.1.
6.5.4 Mark additional vertical lines on the surface to be exposed at distances of 400 mm, 600 mm and 800 mm
from the vertical line drawn in 6.5.1 [see Figure 6c)].
Care should be taken to avoid the possibility of the line influencing the performance of the specimen, for example
by damaging the surface, or increasing its absorbance.
NOTE Some materials discolour on thermal exposure so that the lines and/or marks may be obscured.
6.5.5 Other reference lines (see Figure 15) may be added to allow the flame spread to be recorded by computer
data-logging techniques. If flame spread is recorded by use of additional reference lines, an optional thermocouple
may be mounted on the lower front edge of the specimen holder and the test data-logging started automatically
when this thermocouple measures an increase in temperature of 10 �C (see Figure 16). These methods may also
allow vertical and lateral flame spread rates to be calculated (see clause 11). If the test is performed without using
any software, then the same level of repeatability and reproducibility as in the interlaboratory test (see annex E)
may not be achieved.
6.6 Storage of specimen assemblies
The assemblies of specimen, backing board and spacers prepared as specified in 6.3 shall be stored until required
for testing in the conditioning atmosphere specified in 6.4.1.
10 © ISO 2001 – All rights reserved

Dimensions in millimetres
Key Key
1 Overlap edge distance 1 Exposed side edge of specimen
2 Zero point
a) Location of areas overlapped by the specimen
3 Lower exposed edge of specimen
holder on test specimen
b) Location of zero point on test specimen
Key
1 Exposed side edge of specimen
2 Position of radiant panel
3 Lower exposed edge of specimen
c) Location of reference lines on test specimen
Figure 6 — Location of zero point and reference lines
7 Test apparatus
The test apparatus consists of four main components: a radiant panel, support frame and a specimen support
trolley assembly, which allows the test specimen to be brought into the required configuration in relation to the
radiant panel, the specimen holder and a pilot flame burner.
7.1 Radiant panel support framework, providing the support for the radiant panel, together with the necessary
pipework for air and gas, safety devices, regulators and flowmeters.
7.1.1 Radiant panel support, supporting the radiant panel, with its lower edge at least 500 mm above floor level
to ensure free ventilated test conditions.
The radiating face of the panel shall be vertical and the angle between the face of the panel and the front face of
the specimen shall be (35 � 3)°.
7.1.2 Radiant panel, consisting of an assembly of porous refractory tiles mounted at the front of a stainless-steel
plenum chamber to provide a flat radiating surface of dimensions (480 � 5) mm by (280 � 5) mm.
The plenum chamber shall contain baffle plates and diffusers to distribute the gas/air mixture evenly over the
radiating surface.
A wire screen fixed immediately in front of the radiating face of the panel has been found to increase the irradiance
and to protect the panel from falling debris. A typical wire screen may be made from 3 mm diameter stainless-steel
rods with overall dimensions of 500 mm by 285 mm; 20 horizontally orientated, equally spaced rods may be welded
at all contacts with four vertically orientated cross-rods. Screen support brackets mounted to the sides of the
plenum chamber allow the screen to be held about 15 mm from the face of the radiant panel.
7.2 Gas and air supplies
The combustion gas and air shall be fed to the radiant panel via suitable pressure and flow regulators, safety
equipment and flowmeters. The gas/air mixture enters the plenum chamber through one of the shorter sides to
facilitate easy connection when the panel is mounted from the tubular steel frame.
A suitable supply system includes the following:
–1
a) a supply of natural gas, methane or propane with a flow rate of at least 0,3 l s at a pressure sufficient to
overcome the friction losses through the supply lines, regulators, control valve, flow meters, radiant panel, etc.;
–1
b) an air supply with a flow rate of at least 5 l s at a pressure sufficient to overcome the friction losses through
the supply lines, etc.;
c) separate isolation valves for gas and air;
d) a non-return valve and pressure regulator in the gas supply line;
e) an electrically operated valve to shut off the gas supply automatically in the event of failure of electrical power,
failure of air pressure or fall in temperature at the burner surface;
f) a particulate filter and a flow control valve in the air supply;
–1 –1
g) a flowmeter for natural gas, methane or propane suitable for indicating flows of 0,3 l s to 1,5 l s at ambient
temperature and pressure to a resolution of 1 % or better;
NOTE 1 This is used to assist in setting the gas flow to a value which gives a suitable panel temperature. An absolute
calibration of the flowmeter is unnecessary. Flow rates for the various fuel gases will be different to achieve the required
black body temperature and heat flux distribution on the surface of the test specimen.
–1 –1
h) a flowmeter for air suitable for indicating flows of 1 l s to 12 l s at ambient temperature and pressure to a
resolution of 1 % or better. An absolute calibration is unnecessary.
12 © ISO 2001 – All rights reserved

NOTE 2 All the above items can normally be accommodated within and supported from a tubular steel framework located
remote from the radiant panel.
7.3 Specimen support trolley, incorporating the trolley and the guide rail which locate the specimen holder at
the required position of test in relation to the radiant panel and the pilot flame burner.
The trolley shall allow the specimen holder to be readily moved towards the radiant panel to the required angle of
orientation (see 7.1.1 and Figure 7). The trolley shall also have a debris collection tray fixed below the lower edge
of the specimen holder (see Figure 7).
The specimen holder transport system may be manually or automatically operated to achieve the requirements of
7.1.1. Movement of the trolley shall be consistently achieved to the required tolerances by means of a guide rail
(see Figure 7).
7.4 Specimen holder, typically made from (2 � 0,5) mm thick stainless steel to the dimensions given in Figure 8
so that the exposed surface of the specimen shall be (1 475 � 25) mm high by (975 � 25) mm wide.
It shall be provided with quick-action bolts or clamps to retain the test specimen in position and press it against the
front flanges. Tapered fittings which locate into sockets on the trolley shall be used to mount the specimen holder.
The number of specimen holders required will depend upon the amount of testing envisaged. For specimens
thicker than 200 mm, an additional specimen holder and wider debris tray will be required. The debris tray should
extend 100 mm in front of the specimen base (see Figure 13).
7.5 Pilot flame burner, comprising a (160 � 5) mm length of stainless steel tube with (10 � 1) mm internal
diameter and (12 � 1) mm external diameter, having 15 evenly spaced 1 mm diameter holes drilled radially along
the centreline (see Figure 9). The gas supply pipe connecting with the T-section of the pilot burner shall be made
from continuous stainless steel tubing with a minimum wall thickness of 2 mm. In operation the propane flow shall
–1
be adjusted to about 0,6 l min flow rate (see 9.3). The gas used in the test shall be commercial grade propane
–
having a heating value of approximately 83 MJ�m .
The pilot burner shall be mounted so that its position relative to the face of the test specimen is in line with the top
of the radiant panel as shown in Figure 3. The distance between the burner tube and the face of the specimen shall
be (25 � 1) mm (see Figure 10).
It is important to keep the holes in the pilot burner clean. A soft wire brush has been found suitable to remove
surface contaminants. Nickel-chromium or stainless steel wire, 0,5 mm outside diameter, is suitable for opening the
holes.
The attainment of a satisfactory gas flow to the pilot burner should be done with a dummy specimen in the test
position (see 7.13, 9.3 and Figure 10).
For specimens which are readily compressible by the weight of the pilot flame burner (e.g. high pile carpets), it may
be necessary to carry out a dummy run with no flames on the burner so that the 25 mm separation between the
pilot burner tube and the surface of the specimen can be achieved by adjustment of the flanges on the burner [see
Figures 9b) and 9c)].
7.6 Heat flux meters
–2
At least two heat flux meters of the Schmidt-Boelter (thermopile) type with a nominal range of 0 kW�m to
–2
50 kW�m and a time constant of not more than 3 s (corresponding to a time to reach 95 % of final output of not
more than 10 s) shall be provided, one to form a working instrument and one to be retained as a reference
standard.
NOTE Suitable instruments are commercially available, sometimes referred to as “heat flux transducers”,or “heat flux
gauges”.
Dimensions in millimetres
Key
1 Specimen holder
2 Test specimen
3 Tapered fitting on each side of specimen holder (locates with sockets on trolley framework)
4 Trolley framework supporting specimen holder
5 Debris collection tray
6 Guide rail
Figure 7 — Typical specimen holder and trolley assembly
14 © ISO 2001 – All rights reserved

Dimensions in millimetres
Key
a
Internal
Figure 8 — Typical specimen holder
Dimensions in millimetres
a) Hole separations on burner tube (front view with draught screen omitted)
b) Burner position to specimen surface [side view on a)] c) Moving pilot flame
16 © ISO 2001 – All rights reserved

d) General arrangement of pilot flame burner
Key
1 Steel tube, 12 mm OD, 10 mm ID 4 Propane supply
2 15 1-mm holes 5 Draught screen
3 Specimen surface 6 Adjustable flange
Figure 9 — Pilot flame burner
Dimensions in millimetres
Key
1 Pilot burner tube
2 Front surface of specimen
Figure 10 — Position of non-impinging pilot burner flame to specimen
The target sensing radiator shall be flat, shall occupy an area not more than 10 mm diameter, and shall be coated
2�
with a durable matt black finish. It shall be contained within a water-cooled body whose front face shall be flat,
circular, 25 mm in diameter and coincident with the plane of the receiving face and the target. The whole front of
the water-cooled body shall be highly polished. Radiation shall not pass through a window before reaching the
target. The temperature of the cooling water should be controlled so that the heat flux meter body temperature
remains within a few degrees of room temperature to prevent condensation on the surface.
If heat flux meters of diameter smaller than 25 mm are used, these shall be inserted into a copper sleeve of 25 mm
outside diameter in such a way that good thermal contact is maintained between the sleeve and the water-cooled
heat flux meter body. The end of the sleeve and the receiving face of the heat flux meter shall lie in the same
plane. The heat flux meters shall be robust, simple to set up and use, insensitive to draughts and stable in
calibration. They shall have an accuracy of within (� 3) % and a repeatability within (� 0,5) %.
The calibration of the working heat flux meter shall be checked every 2 months by comparison with the reference
standard heat flux meter (see annex C), which shall be kept securely and not used for any other purpose.
7.7 Recorder
The output from the heat flux meter(s) shall be recorded by any appropriate method.
A strip chart recording millivoltmeter having an input resistance of at least 1 M� is suitable. The sensitivity should
be selected to require less than full-scale deflection with the total heat flux meter chosen. The effective operating
temperature of the radiant panel would not normally exceed 900 °C.
A small digital millivoltmeter capable of indicating signal changes of 10 �V or less will also be found convenient for
monitoring changes in operating conditions of the radiant panel.
7.8 Timing devices
A chronograph and either an electric clock with a sweep second hand or a digital clock shall be provided to
measure time of ignition and flame advance.
The chronograph for timing ignition and initial flame advance may comprise a strip chart recorder with paper speed
–1
of at least 5 mm s .
Both the chronograph paper drive and the electric clock shall be operated through a common switch to initiate
simultaneous operation when the specimen is exposed.
This may be hand operated or actuated automatically as a result of complete specimen insertion.
7.9 Calibration board and support trolley
The calibration board shall be made of non-combustible board (e.g. calcium silicate board) of dimensions
–3
(1 025 � 25) mm by (650 � 5) mm by (11 � 2) mm thick and of oven-dry density (750 � 100) kg�m . The calibration
board shall be provided with five 25 mm diameter holes at the positions given in Figure 11 to accommodate a heat
flux meter for measuring the irradiance in the plane corresponding to the exposed surface of a specimen under
test. The five holes in the calibration board shall align with the centre line of the radiant panel (e.g. they would be
positioned 640 mm above floor-level in the arrangement shown in Figure 3). Either a single heat flux meter may be
used, inserted in each hole in turn, or a number of heat flux meters may be used, but holes which are not occupied
by a heat flux meter shall be filled with removable plugs of the same material as the calibration board.
2� Water cooling of the heat flux meter is required to standardize and define the measurement and to safeguard the heat flux
meter. Failure to supply water cooling can result in overheating and damage to the receiver and loss of calibration of the heat
flux meter. In some cases repairs and recalibration are possible.
18 © ISO 2001 – All rights reserved

Dimensions in millimetres
Figure 11 — Positions of heat flux meter in exposed area of calibration board
The receiving face(s) of the heat flux meter(s) shall (all) be in the plane of the exposed surface of the calibration
board.
The calibration board shall be mounted in a dummy specimen holder (see Figure 12) and located on a specimen
support trolley (see 7.13).
7.10 Backing boards and spacers
Backing boards shall be cut from non-combustible board (e.g. calcium silicate board) (11 � 2) mm thick with the
–3
same dimensions as the test specimen and an oven-dry density of (750 � 100) kg m (see ISO/TR 14697).
Spacers used to create the air gap specified in 6.3.6 shall be made of the same material as the backing board, cut
into (25 � 2) mm wide strips and attached to the whole perimeter of the backing board.
Backing boards and spacers may be re-used if they are not contaminated by combustible residues. Immediately
before re-use, however, they shall have been conditioned in the atmosphere specified in 6.4.1. If there is any doubt
about the cleanliness of a backing board or spacer, it shall be placed in a ventilated oven at a temperature of
(60 � 5) °C for a period of 2 h in an attempt to remove any volatile residue. If there is still any doubt about the
condition, it shall be discarded.
7.11 Video camera
A video camera, placed at a location [see 9.1 e)] to provide a clear view of the whole test specimen, along with an
appropriate video recording device shall be used.
7.12 Pyrometer
A radiation pyrometer with a range of 700 °Cto 850 °C (black body temperature) and an accuracy of � 5 °C
suitable for viewing a circular area (30 � 5) mm in diameter at a distance of about 750 mm shall be used to control
the thermal output of the radiant panel. The sensitivity of the pyrometer shall be substantially constant between the
wave lengths of 1 mm and 9 mm.
The pyrometer may be positioned on the dummy specimen trolley (s
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