ISO 5660-1:2002

INTERNATIONAL ISO
STANDARD 5660-1
Second edition
2002-12-15
Reaction-to-fire tests — Heat release,
smoke production and mass loss rate —
Part 1:
Heat release rate (cone calorimeter method)
Essais de réaction au feu — Débit calorifique, taux de dégagement de
fumée et taux de perte de masse —
Partie 1: Débit calorifique (méthode au calorimètre conique)

Reference number
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ii ISO 2002 – All rights reserved

Contents Page
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Principle . 3
6 Apparatus . 3
7 Suitability of a product for testing . 6
8 Specimen construction and preparation . 7
9 Test environment . 9
10 Calibration . 9
11 Test procedure . 12
12 Calculations . 14
13 Test report . 16
Annexes
A Commentary and guidance notes for operators. 24
B Resolution, precision and bias . 26
C Mass loss rate and effective heat of combustion . 31
D Testing in the vertical orientation. 32
E Calibration of the working heat flux meter. 35
F Calculation of heat release with additional gas analysis . 36
Bibliography. 39
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ISO 2002 – All rights reserved iii

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
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 5660 may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 5660-1 was prepared by Technical Committee ISO/TC 92, Fire safety, Subcommittee
SC 1, Fire initiation and growth.
This second edition cancels and replaces the first edition (ISO 5660-1:1993), which has been technically revised.
ISO 5660 consists of the following parts, under the general title Reaction-to-fire tests — Heat release, smoke
production and mass loss rate:
— Part 1: Heat release rate (cone calorimeter method)
— Part 2: Smoke production rate (dynamic measurement)
— Part 3: Guidance on heat and smoke release rate
Annexes A, B, C, D, E and F of this part of ISO 5660 are for information only.
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iv ISO 2002 – All rights reserved

INTERNATIONAL STANDARD ISO 5660-1:2002(E)
Reaction-to-fire tests — Heat release, smoke production and mass
loss rate —
Part 1:
Heat release rate (cone calorimeter method)
1 Scope
This part of ISO 5660 specifies a method for assessing the heat release rate of a specimen exposed in the horizontal
orientation to controlled levels of irradiance with an external igniter. The heat release rate is determined by
measurement of the oxygen consumption derived from the oxygen concentration and the flow rate in the combustion
product stream. The time to ignition (sustained flaming) is also measured in this test.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO 5660. 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 5660 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 554:1976, Standard atmospheres for conditioning and/or testing — Specifications
ISO 13943:2000, Fire safety — Vocabulary
ISO/TR 14697:1997, Fire tests — Guidance on the choice of substrates for building products
3 Terms and definitions
For the purposes of this part of ISO 5660, the terms and definitions given in ISO 13943 and the following apply.
3.1
essentially flat surface
surface whose irregularity from a plane does not exceed ±1mm
3.2
flashing
existence of flame on or over the surface of the specimen for periods of less than 1s
3.3
ignition
onset of sustained flaming as defined in 3.10
3.4
irradiance
〈at a point on a surface〉 quotient of the radiant flux incident on an infinitesimal element of surface containing the
point, and the area of that element
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ISO 2002 – All rights reserved 1

NOTE Convective heating is negligible in the horizontal specimen orientation. For this reason, the term “irradiance” is used
instead of “heat flux” throughout this part of ISO 5660 as it best indicates the essentially radiative mode of heat transfer.
3.5
material
single substance or uniformly dispersed mixture
EXAMPLE Metal, stone, timber, concrete, mineral fibre and polymers.
3.6
orientation
plane in which the exposed face of the specimen is located during testing, with either the vertical or horizontal face
upwards
3.7
oxygen consumption principle
proportional relationship between the mass of oxygen consumed during combustion and the heat released
3.8
product
material, composite or assembly about which information is required
3.9
specimen
representative piece of the product which is to be tested together with any substrate or treatment
NOTE For certain types of product, for example products that contain an air gap or joints, it may not be possible to prepare
specimens that are representative of the end-use conditions (see clause 7).
3.10
sustained flaming
existence of flame on or over the surface of the specimen for periods of over 10 s
3.11
transitory flaming
existence of flame on or over the surface of the specimen for periods of between 1 s and 10 s
4 Symbols
See Table 1.
Table 1 — Symbols and their designations
Symbol Designation Unit
Initially exposed surface area of the specimen m
A
s
1/2 1/2 1/2
Orifice flow meter calibration constant m · g · K
C
−1
Net heat of combustion kJ· g
∆h
c
−1
Effective net heat of combustion MJ· kg
∆h
c,eff
m Mass of the specimen g
Total mass loss g
∆m
m Mass of the specimen at the end of the test g
f
m Mass of the specimen at sustained flaming g
s
•
−2 −1
Average mass loss rate per unit area between 10 % and 90 % of mass loss g· m · s
m
A,10−90
g
m Mass of the specimen at 10 % of total mass loss
m Mass of the specimen at 90 % of total mass loss g
•
−1
Mass loss rate of specimen g· s
m
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Table 1 — Symbols and their designations (continued)
Symbol Designation Unit
• −1
Mass flow rate in exhaust duct kg· s
m
e
Orifice meter pressure differential Pa
∆p
•
Heat release rate kW
q
•
−2
Heat release rate per unit area kW· m
q
A
•
−2
Maximum value of the heat release rate per unit area kW· m
q
A,max
•
−2
kW· m
Average heat release rate per unit area over the period starting at t and ending 180 s later
q ig
A,180
• −2
Average heat release rate per unit area over the period starting at t and ending 300 s later kW· m
q ig
A,300
−2
MJ· m
Q Total heat released per unit area during the entire test
A,tot
r Stoichiometric oxygen/fuel mass ratio 1
o
t Time s
t Delay time of the oxygen analyser s
d
t Time to ignition (onset of sustained flaming) s
ig
∆t Sampling time interval s
t Time at 10 % of total mass loss s
t Time at 90 % of total mass loss s
T Absolute temperature of gas at the orifice meter K
e
X Oxygen analyser reading, mole fraction of oxygen 1
O
X Initial value of oxygen analyser reading 1
O
X Oxygen analyser reading, before delay time correction 1
O
5 Principle
This test method is based on the observation that, generally, the net heat of combustion is proportional to the amount
of oxygen required for combustion. The relationship is that approximately 13,1× 10 kJ of heat are released per
kilogram of oxygen consumed. Specimens in the test are burned under ambient air conditions, while being subjected
2 2
to a predetermined external irradiance within the range of 0 kW/m to 100 kW/m and measurements are made of
oxygen concentrations and exhaust gas flow rates.
The test method is used to assess the contribution that the product under test can make to the rate of evolution of
heat during its involvement in fire. These properties are determined on small representative specimens.
6Apparatus
A schematic representation of the apparatus is given in Figure 1. The individual components are described in detail
in 6.1 to 6.5.
With minor modifications to the apparatus, specimens may be tested in the vertical orientation. Annex D gives
guidance on these modifications.
6.1 Cone-shaped radiant electrical heater
The active element of the heater shall consist of an electrical heater rod, capable of delivering 5 000 W at the
operating voltage, tightly wound into the shape of a truncated cone (see Figure 2). The heater shall be encased on
the outside with a double-wall stainless-steel cone, filled with a refractory fibre blanket of nominal thickness 13 mm
and nominal density 100 kg/m . The irradiance from the heater shall be maintained at a preset level by controlling the
average temperature of three thermocouples (type K stainless-steel sheathed thermocouples have proved suitable
but Inconel or other high-performance materials are also acceptable), symmetrically positioned and in contact with,
but not welded to, the heater element (see Figure 2). Either 3,0 mm outside diameter sheathed thermocouples with
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ISO 2002 – All rights reserved 3

exposed hot junction or 1,0 mm to 1,6 mm outside diameter sheathed thermocouples with unexposed hot junction
shall be used. The heater shall be capable of producing irradiance on the surface of the specimen of up to
100 kW/m . The irradiance shall be uniform within the central 50 mm× 50 mm area of the exposed specimen
surface, to within ±2%.
6.2 Radiation shield
The cone heater shall be provided with a removable radiation shield to protect the specimen from the irradiance prior
to the start of a test. The shield shall be made of non-combustible material, with a total thickness not exceeding
12 mm. The shield shall be one of the following, either
a) water-cooled and coated with a durable matt black finish of surface emissivity � = 0,95± 0,05, or
b) not water-cooled, which may be either metal with a reflective top surface or ceramic in order to minimize radiation
transfer.
The shield shall be equipped with a handle or other suitable means for quick insertion and removal. The cone heater
base plate shall be equipped with a mechanism for moving the shield into position.
6.3 Irradiance control
The irradiance control system shall be properly tuned so that it maintains the average temperature of the heater
◦
thermocouples during the calibration described in 10.1.2 at the preset level to within ± 10 C.
6.4 Weighing device
The weighing device shall have an accuracy of ± 0,1 g or better, measured according to the calibration procedure
described in 10.2.2. The weighing device shall be capable of measuring the mass of specimens of at least 500 g. The
weighing device shall have a 10 % to 90 % response time of 4 s or less, as determined according to the calibration
described in 10.1.3. The output of the weighing device shall not drift by more than 1g over a 30-min period, as
determined with the calibration described in 10.1.4.
6.5 Specimen holder
The specimen holder is shown in Figure 3. The specimen holder shall have the shape of a square pan with an
opening of (106± 1) mm×(106± 1) mm at the top, and a depth of (25± 1) mm. The holder shall be
constructed of stainless steel with a thickness of (2,4± 0,15) mm. It shall include a handle to facilitate insertion and
removal, and a mechanism to ensure central location of the specimen under the heater and proper alignment with
the weighing device. The bottom of the holder shall be lined with a layer of low density (nominal density 65 kg/m )
refractory fibre blanket with a thickness of at least 13 mm. The distance between the bottom surface of the cone
heater and the top of the specimen shall be adjusted to be (25± 1) mm, except for dimensionally unstable materials
(60± 1) mm
for which the distance shall be (see 7.5).
6.6 Retainer frame
The frame shall be constructed of stainless steel with a thickness of (1,9± 0,1) mm, in the shape of a box with an
inside dimension of each side (111± 1) mm and a height of (54± 1) mm. The opening for the specimen face shall
be (94,0± 0,5) mm square as shown in Figure 4. The retainer frame shall have an appropriate means to secure it
to the specimen holder with a specimen in position.
6.7 Exhaust gas system with flow measuring instrumentation
The exhaust gas system shall consist of a centrifugal exhaust fan rated for the operating temperatures, a hood, intake
and exhaust ducts for the fan, and an orifice plate flow meter (see Figure 5). The distance between the bottom of the
hood and the specimen surface shall be (210± 50) mm. The exhaust system shall be capable of developing flows
up to 0,024 m /s, under standard conditions of temperature and pressure. The recommended location of the fan is
indicated on Figure 5. As an alternative, it is acceptable to locate the fan further downstream and to have the
measuring orifice before the fan, provided that the requirements described in the remainder of this clause are
fulfilled.
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A restrictive orifice with an internal diameter of (57± 3) mm shall be located between the hood and the duct to
promote mixing.
A ring sampler shall be located in the fan intake duct for gas sampling, (685± 15) mm from the hood (see Figure 5).
The ring sampler shall contain 12small holes with a diameter of (2,2± 0,1) mm, to average the stream
composition, with the holes facing away from the flow to avoid clogging with soot.
The temperature of the gas stream shall be measured using a 1,0 mm to 1,6 mm outside diameter sheathed-junction
thermocouple or a 3mm outside diameter exposed-junction thermocouple positioned in the exhaust stack on the
centreline and (100± 5) mm upstream from the measuring orifice plate.
The flow rate shall be determined by measuring the differential pressure across a sharp edge orifice [internal
diameter (57± 3) mm, thickness (1,6± 0,3) mm] in the exhaust stack, at least 350 mm downstream from the fan,
if the latter is located as shown on Figure 5. If the fan is located further downstream than indicated in Figure 5, it is
acceptable to locate the orifice plate between the ring sampler and the fan. However, in that case the length of the
straight duct section on both sides of the orifice plate shall be at least 350 mm.
6.8 Gas sampling apparatus
The gas sampling apparatus shall incorporate a pump, a filter to prevent entry of soot, a cold trap to remove most of
the moisture, a by-pass system set to divert all flow except that required for the gas analysers, a further moisture trap
and a trap for CO removal. A schematic view of an example of the gas sampling apparatus is shown in Figure 6.
Other arrangements which satisfy the requirements may be used. The transport delay time of the oxygen analyser,
t , shall be determined according to 10.1.5, and shall not exceed 60 s.
d
NOTE If an (optional) CO analyser is used, the equations to calculate the heat release rate can be different from those for the
standard case (see clause 12 and annex F).
6.9 Ignition circuit
External ignition is accomplished by a spark plug powered from a 10 kV transformer or spark igniter. The spark plug
shall have a gap of (3,0± 0,5) mm. The electrode length and location of the spark plug shall be such that the spark
gap is located (13± 2) mm above the centre of the specimen, except for dimensionally unstable materials for which
the distance shall be (48± 2) mm (see 7.5).
6.10 Ignition timer
The ignition timer shall be capable of recording elapsed time to the nearest second and shall be accurate to within
1s in 1h.
6.11 Oxygen analyser
The oxygen analyser shall be of the paramagnetic type, with a range of at least 0 % oxygen to 25 % oxygen. The
analyser shall exhibit a drift of not more than 50 parts per million of oxygen over a period of 30 min, and a noise of
not more than 50 parts per million of oxygen during this 30-min period, as measured according to 10.1.6. Since
oxygen analysers are sensitive to stream pressures, the stream pressure shall be regulated (upstream of the
analyser) to minimize flow fluctuations, and the readings from the analyser compensated with an absolute pressure
transducer to allow for atmospheric pressure variations. The analyser and the absolute pressure transducer shall be
◦
located in an isothermal environment. The temperature of the environment shall be maintained to within 2 C of a
◦ ◦
preset value between 30C7 and 0 C. The oxygen analyser shall have a 10 % to 90 % of full-scale response time
of less than 12 s, as measured according to 10.1.5.
6.12 Heat flux meters
The working heat flux meter shall be used to calibrate the heater (see 10.2.5). It shall be positioned at a location
equivalent to the centre of the specimen face during this calibration.
This heat flux meter shall be of the Schmidt-Boelter (thermopile) type with a design range of (100± 10) kW/m . The
target receiving the heat shall be flat, circular, of approximately 12,5 mm in diameter and coated with a durable matt
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ISO 2002 – All rights reserved 5

black finish of surface emissivity � = 0,95± 0,05. The target shall be water-cooled. A cooling temperature which
would cause condensation of water on the target surface of the heat flux meter shall not be used.
Radiation shall not pass through any window before reaching the target. The instrument shall be robust, simple to set
±3%
up and use, and stable in calibration. The instrument shall have an accuracy of within and a repeatability to
within .± 0,5 %
The calibration of the working heat flux meter shall be checked according to 10.3.1, by comparison with two
instruments of the same type as the working heat flux meter and of similar range held as reference standards and not
used for any other purpose (see annex E). One of the reference standards shall be fully calibrated at a standardizing
laboratory at yearly intervals.
6.13 Calibration burner
The calibration burner shall be constructed from tube with a square or circular orifice with an area of
(500± 100) mm covered with wire gauze through which the methane diffuses. The tube is packed with refractory
fibre to improve uniformity of flow. The calibration burner is suitably connected to a metered supply of methane of at
least 99,5 % purity. The accuracy of the flow meter shall be ±2% of the readout, corresponding to a heat release
rate of 5kW. The accuracy verification shall be performed according to 10.3.3.
6.14 Data collection and analysis system
The data collection and analysis system shall have facilities for recording the output from the oxygen analyser, the
orifice meter, the thermocouples and the weighing device. The data collection system shall have an accuracy
◦
corresponding to at least 50 parts per million of oxygen for the oxygen channel, 0,5 C for the temperature
measuring channels, 0,01 % of full-scale instrument output for all other instrument channels, and at least 0,1 % for
time. The system shall be capable of recording data every second. The system shall be capable of storing a minimum
of 720 data per parameter. The raw data recorded for each test shall be stored so that it can be recovered and used
to check the accuracy of the software.
6.15 Optional side screens
For operational or safety reasons, it is permitted to guard the heater and sample holder with side screens. However,
it shall be demonstrated that the presence of the screens does not affect the ignition time and heat release rate
measurements according to the procedure described in 10.1.7.
If the screens form an enclosure, attention is drawn to the fact that there is a possible explosion hazard when the
instrument is not operated under conditions prescribed by this part of ISO 5660, in particular for experiments in an
oxygen-enriched atmosphere. If an explosion hazard exists, proper precautions shall be taken to protect the operator,
e.g. by installing an explosion vent facing away from the operator.
7 Suitability of a product for testing
7.1 Surface characteristics
A product having one of the following properties is suitable for testing:
a) an essentially flat exposed surface;
b) a surface irregularity which is evenly distributed over the exposed surface provided that
1) at least 50 % of the surface of a representative 100 mm square area lies within a depth of 10 mm from a
plane taken across the highest points on the exposed surface, or
2) for surfaces containing cracks, fissures or holes not exceeding 8mm in width nor 10mm in depth, the total
area of such cracks, fissures or holes at the surface does not exceed 30 % of a representative 100 mm
square area of the exposed surface.
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When an exposed surface does not meet the requirements of either 7.1 a) or 7.1 b), the product shall be tested in a
modified form complying as nearly as possible with the requirements given in 7.1. The test report shall state that the
product has been tested in a modified form, and clearly describe the modification.
7.2 Asymmetrical products
A product submitted for this test can have faces which differ or can contain laminations of different materials arranged
in a different order in relation to the two faces. If either of the faces can be exposed in use within a room, cavity or
void, then both faces shall be tested.
7.3 Materials of short burning time
For specimens of short burning time (3 min or less), the heat release rate measurements shall be taken at not more
than 2s intervals. For longer burning times, 5s intervals may be used.
7.4 Composite specimens
Composite specimens are suitable for testing, provided that they are prepared as specified in 8.3 and are exposed in
a manner typical of end use conditions.
7.5 Dimensionally unstable materials
Samples that intumesce or deform so that they contact the spark plug prior to ignition, or the underside of the cone
heater after ignition, shall be tested with the separation of 60 mm between the base plate of the cone heater and the
upper surface of the specimen. In this case the heater calibration (see 10.2.5) shall be performed with the heat flux
meter positioned 60 mm below the cone heater base plate. It must be stressed that the time to ignition measured with
this separation is not comparable to that measured with the separation of 25 mm.
Other dimensionally unstable products, for example products that warp or shrink during testing, shall be restrained
against excessive movement. This shall be accomplished with four tie wires, as described below. Metal wires of
(1,0± 0,1) mm diameter and at least 350 mm long shall be used. The sample shall be prepared in the standard way
as described in clause 8. A tie wire is then looped around the sample holder and retainer frame assembly, so that it
is parallel to and approximately 20 mm away from one of the four sides of the assembly. The ends of the wire are
twisted together such that the wire is pulled firmly against the retainer frame. Excess wire is trimmed from the twisted
section before testing. The three remaining wires shall be fitted around the specimen holder and retainer frame
assembly in a similar manner, parallel to the three remaining sides.
8 Specimen construction and preparation
8.1 Specimens
8.1.1 Unless otherwise specified, three specimens shall be tested at each level of irradiance selected and for each
different exposed surface.
8.1.2 The specimens shall be representative of the product and shall be square with sides measuring 100 mm.
−2
8.1.3 Products with a normal thickness of 50 mm or less shall be tested using their full thickness.
8.1.4 For products with a normal thickness of greater than 50 mm, the requisite specimens shall be obtained by
cutting away the unexposed face to reduce the thickness to 50 mm.
8.1.5 When cutting specimens from products with irregular surfaces, the highest point on the surface shall be
arranged to occur at the centre of the specimen.
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ISO 2002 – All rights reserved 7

8.1.6 Assemblies shall be tested as specified in 8.1.3 or 8.1.4 as appropriate. However, where thin materials or
composites are used in the fabrication of an assembly, the nature of any underlying construction can significantly
affect the ignition and burning characteristics of the exposed surface.
The influence of the underlying layers shall be understood and care taken to ensure that the test result obtained on
any assembly is relevant to its use in practice.
When the product is a material or composite which would normally be attached to a well-defined substrate, it shall be
tested in conjunction with that substrate using the recommended fixing technique, for example bonded with the
appropriate adhesive or mechanically fixed. In the absence of a unique or well-defined substrate, an appropriate
substrate for testing shall be selected in accordance with ISO/TR 14697.
8.1.7 Products that are thinner than 6mm shall be tested with a substrate representative of end-use conditions,
such that the total specimen thickness is 6mm or more.
8.2 Conditioning of specimens
◦
Before the test, specimens shall be conditioned to constant mass at a temperature of (23± 2) C, and a relative
humidity of (50± 5) % in accordance with ISO 554.
Constant mass is considered to be reached 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 test piece or 0,1 g, whichever is the greater.
Materials such as polyamides, which require more than one week in conditioning to reach equilibrium may be tested
[1]
after conditioning in accordance with ISO 291 . This period shall be not less than one week, and shall be described
in the test report.
8.3 Preparation
8.3.1 Specimen wrapping
A conditioned specimen shall be wrapped in a single layer of aluminum foil, of 0,025 mm to 0,04 mm thickness, with
the shiny side towards the specimen. The alminium foil shall be pre-cut to a size to cover the bottom and sides of the
specimen and extend 3mm or more beyond the upper surface of the specimen. The specimen shall be placed in the
middle of the foil and the bottom and sides shall be wrapped. The excess foil above the top surface shall be cut if
necessary so that it does not extend more than 3mm above the top surface of the specimen. The excess foil at the
corners shall be folded around the corners to form a seal around the top surface of the specimen. After wrapping, the
wrapped specimen shall be placed in the specimen holder and covered by a retainer frame. No aluminium foil shall
be visible after the procedure is completed.
For soft specimens, a dummy specimen having the same thickness as the specimen to be tested may be used to pre-
shape the aluminium foil.
8.3.2 Specimen preparation
All specimens shall be tested with the retainer frame shown in Figure 4. The following steps shall be taken to prepare
a specimen for testing:
a) put the retainer frame on a flat surface facing downwards;
b) insert the foil-wrapped specimen into the frame with the exposed surface facing downwards;
c) put layers of refractory fibre blanket (nominal thickness 13 mm, nominal density 65 kg/m ) on top until at least
one full layer, and not more than two layers, extend above the rim of the frame;
d) fit the sample holder into the frame on top of the refractory fibre and press down;
e) secure the retainer frame to the specimen holder.
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8 ISO 2002 – All rights reserved

9 Test environment
The apparatus shall be located in an essentially draught-free environment in an atmosphere of relative humidity of
◦ ◦
20 % 80 % 15C30 C
between and and a temperature between and .
10 Calibration
10.1 Preliminary calibrations
10.1.1 General
The calibrations in this section, except for that in 10.1.7, shall be performed before conducting experiments, when
commissioning a Cone calorimeter; or after maintenance, repair or replacement of the heater assembly or irradiance
control system (10.1.2), the weighing device (10.1.3 and 10.1.4), the oxygen analyser or other major components of
the gas analysis system (10.1.5 and 10.1.6). The calibration tests to determine the effect of side screens in 10.1.7
are conducted at the time the screens are installed. For a new instrument that is delivered with side screens, this
shall be done by the manufacturer.
10.1.2 Irradiance control system response characteristics
Turn on power to the cone heater and the exhaust fan. Set an irradiance of (50± 1) kW/m , and an exhaust flow
rate of (0,024± 0,002) m /s. After reaching equilibrium of the heater, record the average heater temperature. Test
a specimen of black poly(methyl methacrylate) (PMMA) according to the procedure in clause 11. The PMMA
specimen shall have a thickness of at least 6 mm. The average heat release rate recorded over the first 3 min
following ignition shall be approximately 530 kW/m . During the test, record the average heater temperature at 5s
intervals.
10.1.3 Weighing device response time
The cone heater shall not be turned on for this calibration. Place an empty specimen holder with a (250± 25) g
non-combustible weightpiece on the weighing device. The weightpiece accounts for the retainer frame, which is not
used during this calibration. Measure the weighing device output, and mechanically or electronically adjust the value
to zero. Gently add a second non-combustible weightpiece with a mass of (250± 25) g on the holder and record the
weighing device output. After equilibrium is reached, gently remove the second weightpiece from the holder, and
again record the weighing device output. Determine the response time of the weighing device as the average of the
times for the weighing device output to change from 10 % to 90 % of its ultimate deflection.
10.1.4 Weighing device output drift
Set the height of the cone heater to the same position as when testing a specimen with the retainer frame. Place a
thermal barrier on the weighing device. Turn on power to the exhaust fan and cone heater. Set an exhaust flow rate
3 2
of (0,024± 0,002) m /s and an irradiance of (50± 1) kW/m . After reaching equilibrium of the heater temperature,
remove the thermal barrier and place an empty specimen holder with a (250± 25) g weightpiece on the weighing
device. The weightpiece accounts for the retainer frame, which is not used during this calibration. After equilibrium is
reached, measure the weighing device output and mechanically or electronically adjust the value to zero. Gently add
a second weightpiece with a mass of (250± 25) g on the specimen holder. After equilibrium is reached, record the
weighing device output. After 30 min, record the weighing device output. Calculate the drift of the weighing device
output as the absolute value of the difference of the initial and final values.
10.1.5 Oxygen analyser delay and response times
The cone heater shall not be turned on for this calibration. Turn on the exhaust fan, and set an exhaust flow rate of
(0,024± 0,002) m /s. Determine the delay time of the oxygen analyser by delivering a methane flow rate
approximately equivalent to 5kW to the calibration burner. Light the burner outside the hood and allow the flame to
©
ISO 2002 – All rights reserved 9

stabilize. Quickly introduce the burner underneath the hood, and leave the burner in position for 3 min. Then, remove
the burner from underneath the hood and turn off the methane supply. Record the output of the analyser from the
moment of insertion of the burner underneath the hood, until 3 min after removal of the burner. The turn-on delay is
the time difference between insertion of the burner and the oxygen reading reaching 50 % of its ultimate deflection.
Calculate the turn-off delay similarly. The delay time t is the average of at least three turn-on and turn-off delays.
d
The oxygen concentration at a given time shall be taken as the concentration registered after the time interval t .
d
The response time of the oxygen analyser is calculated as the average for the turn-on and turn-off experiments of the
time for the oxygen analyser output to change from 10 % to 90 % of its ultimate deflection.
NOTE For the purpose of measurement of the oxygen analyser delay and response time, the methane flow rate need not be
controlled accurately, because the delay and response time is not sensitive to the oxygen level.
10.1.6 Oxygen analyser output noise and drift
The cone heater shall not be turned on for this calibration. Turn on the exhaust fan, and set an exhaust flow rate of
(0,024± 0,002) m /s. Feed the oxygen analyser with oxygen-free nitrogen gas. After 60 min, switch to dried
ambient air from the exhaust duct at the normal flow rate and pressure as for the sample gases. After reaching
equilibrium, adjust the oxygen analyser output to (20,95± 0,01) %. Start recording the oxygen analyser output at
5 s intervals for a period of 30 min. Determine the drift by use of a least-squares fitting procedure to fit a straight line
through the data points. For the straight line fit, the absolute value of the difference between the reading at 0 min and
at 30 min represents the short-term drift. Determine the noise by computing the root-mean-square deviation around
the linear trend line according to the following formula:
�
� n
�
� 2
x
� i
i=1
r.m.s. =
n
where x is the absolute difference between the data point and the linear trend line.
i
Record this r.m.s. noise value in terms of parts per million of oxygen.
10.1.7 Effect of side screens
To evaluate the effect of side screens on the test results, six specimens of black cast poly(methyl methacrylate)
(PMMA) of thickness (25± 0,5) mm shall be tested at (50± 1) kW/m according to the procedure described in
clause 11. The first three tests shall be conducted with the screens removed, the remaining three tests with the
• •
q q
screens in place. The screens are permitted if the differences between the average values of t , and
ig A,180 A,max
for the two test series are found to be statistically insignificant according to a two-sided t-test at a significance level of
• •
q q
5%. This t-test shall be performed for the three variables (t , , and ) according to the following
ig A,180 A,max
procedure:
a) for the two series of three tests, calculate the averages via
�
x
i
i=1
x = (1)
and
�
y
i
i=1
y = (2)
©
10 ISO 2002 – All rights reserved

b) calculate the pooled standard deviation, s , from
p
�
�
3 3
�� �
2 2
�
(x −x) + (y −y)
i i
�
i=1 i=1
s = (3)
p
c) calculate the t-test statistic as
� �
� �
x−y
� �
t = (4)
S
� �
0,816 5s
p
The t-test is successful if the value of the test statistic does not exceed 2,776, or if the two averages are equal.
10.2 Operating calibrations
10.2.1 General
The following calibrations shall be performed at the start of testing each day, in the order given below. The heater
calibration shall also be performed when changing to a different irradiance level.
10.2.2 Weighing device accuracy
The weighing device shall be calibrated with standard weightpieces in the range of the test specimen mass. The
cone heater shall be turned off and the apparatus shall be cooled down to ambient temperature before this
calibration is performed. Place an empty specimen holder with a (250± 25) g weightpiece on the weighing device.
The weightpiece accounts for the retainer frame, which is not used during this calibration. Measure the weighing
device output, and mechanically or electronically adjust the value to zero. Gently add a weight piece with a mass
between 50 g and 200 g on the holder and measure the weighing device output after it reaches a steady value.
Repeat this procedure at least four times after adding weightpieces of the same mass range. At the end of the
calibration, the total mass of all weightpieces on the holder shall be at least 500 g. The accuracy of the weighing
device is determined as the maximum difference between the mass of the weightpieces and the weighing device
output recorded during the calibration.
10.2.3 Oxygen analyser
Zero and calibrate the oxygen analyser. This calibration may be performed with the cone heater operating or not, but
shall not be performed during heater warm-up. Turn on the exhaust fan, and set an exhaust flow rate of
(0,024± 0,002) m /s. For zeroing, feed the analyser with oxygen-free nitrogen gas, with the same flow rate and
pressure as for the sample gases. Adjust the analyser response to (0,00± 0,01) %. Calibration shall be similarly
achieved using dried ambient air and adjusting for a response of (20,95± 0,01) %. Carefully monitor analyser flow
rates and set them to be equal to the flow rate used when testing specimens. After each specimen has been tested,
ensure that a response level of (20,95± 0,01) % is obtained using dried ambient air.
10.2.4 Heat release rate calibration
Perform a heat release rate calibration to determine the orifice constant C. This calibration may be performed with
the cone heater operating or not, but shall not be performed during heater warm-up. Turn on the exhaust fan, and set
an exhaust flow rate of (0,024± 0,002) m /s. Start collecting baseline data at 5-s intervals for a period of at least
1-min. Introduce methane into the calibration burner using a calibrated flow meter at a flow rate corresponding to
•
q
=(5± 0,5) kW based on the net heat of combustion of methane (50,0× 10 ) kJ/kg. After the outputs from all
b
instruments reach equilibrium, collect data at 5-s intervals over a 3-min period. Calculate the orifice constant C
•
q
according to equation (5) in clause 12, using averages over the 3-min period of the measured values of , T , ∆p
b e
©
ISO 2002 – All rights reserved 11

and X . X is determined as the average of the oxygen analyser output measured during the 1-min baseline
O
2 O
measurements.
An alternative procedure for performing this calibration consists of burning a suitable liquid fuel (e.g. ethanol) in a
special pan that is placed on the weighing device. The average theoretical heat release rate is then obtained as the
total mass of fuel burnt multiplied by the net heat of combustion of the fuel, and divided by the duration of flaming.
10.2.5 Heater calibration
At the start of testing each day or when changing to a different irradiance level, adjust the irradiance control system
so that the conical heater produces the required irradiance to within ±2%, as measured by the heat flux meter. No
specimen or specimen holder shall be used when the heat flux meter is inserted into the calibration position. Operate
the cone heater for at least 10 min when stable at set point, and ensure that the controller is within its proportional
band before beginning this calibration.
10.3 Less frequent calibrations
10.3.1 Operating heat flux meter calibration
At maximum intervals of 100 working hours, check the operating heat flux meter against the reference heat flux
meter using one of the procedures described in annex E. Comparisons shall be made at irradiance levels of (10, 25,
35, 50, 65, 75 and 100) kW/m . The readings from the two m
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