ISO 3957:2025
(Main)Reaction to fire tests — Parallel panel test method for wall systems — Measurement of heat release and smoke production
Reaction to fire tests — Parallel panel test method for wall systems — Measurement of heat release and smoke production
This document specifies a large-scale fire test method for measuring the heat release rate (HRR) and the smoke-production rate (SPR) of wall systems. The fire scenario covered in this document is representative of severe fires originating in near wall or corner locations of an exterior or interior wall construction. A severe fire scenario is defined that imparts a heat flux on the order of 100 kW/m2 to the wall systems. These include exterior fire scenarios such as dumpster, balcony storage fires, and vehicle fires originating outside buildings. Fires caused by combustible storage inside unsprinklered or inadequately sprinklered occupancies, such as warehouse and manufacturing occupancies, represent a few examples of severe interior fires. This document measures the HRR and SPR in accordance with ISO 24473. This document also provides guidelines for heat release and smoke production performance limits, developed and used for risk evaluation by the insurance industry. The test method is not applicable to scenarios where a fire initiates within an air cavity, if present, of an exterior wall system. The test method does not incorporate a window structure and is therefore not applicable to fire spread hazards resulting from inadequately protected window openings in a post-flashover fire scenario.
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International
Standard
ISO 3957
First edition
Reaction to fire tests — Parallel
2025-07
panel test method for wall systems
— Measurement of heat release and
smoke production
Reference number
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 2
5 Principle . 3
6 Test facility and instrumentation section . 4
7 Apparatus . 4
7.1 General .4
7.2 Metal frames .5
7.3 Sand burner and fuel supply.6
7.4 Weighing platform (Optional) .9
7.5 Assembly preparation .9
7.6 Instrumentation and videography .10
7.7 Data recording and processing .10
8 Calibration .11
8.1 Gas analyser system .11
8.2 Propane sand burner calibration .11
8.3 Heat flux exposure to parallel walls . 12
8.4 Smoke measurement system . 13
8.5 System response . 13
8.6 Weighing platform (optional) . . 13
9 Test procedure and settings .13
10 Calculations and analysis . 14
11 Test report . 14
Annex A (informative) Literature background and performance guidance .16
Annex B (informative) Calorimeter design . 19
Annex C (informative) Propane burner calibrations .23
Annex D (informative) Repeatability .27
Bibliography .36
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 92, Fire safety, Subcommittee SC 1, Fire
initiation and growth.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
This large-scale fire test standard is developed for the purpose of measuring the heat release rate (HRR) and
the smoke-production rate (SPR) of exterior and interior wall systems, exposed under severe fire scenarios
using a parallel panel setup. Severe fire exposure to an exterior wall system can be either caused by spill
plumes from a window, such as in a post-flashover compartment fire, or an exterior fire source such as in a
dumpster, vehicle, or balcony storage. Some extreme scenarios for an exterior fire include city conflagration
(e.g. after an earthquake) or wildland-urban-interface (WUI) fires. Severe interior wall fires can be caused
by combustible storage located inside a facility, such as warehouse and manufacturing occupancies, close
to the corners of wall system. A common factor of such fire scenarios is the absence or an inadequacy of the
traditional active fire protection safeguards (e.g. sprinklers) leading to unmitigated heat exposures to wall
systems.
A sufficiently high heat flux is required to simulate such fire exposures ― a high heat flux can reveal the
flammability of the encapsulated materials used in the wall systems, as well as the vulnerabilities of facers,
[1]
joints and other components. Literature shows that severe fire exposure to wall systems is in the order
of 100 kW/m . For this purpose, three large-scale fire tests are known to simulate realistically severe fire
exposures of about 100 kW/m , and are used to evaluate the performance of both exterior and interior wall
[2]to[5]
systems . These three large-scale fire tests include the 7,6 m (25-ft) high corner fire test, 15 m (50-ft)
high corner fire test, and 4,9 m (16-ft) high parallel panel test of the ANSI/FM 4880 standard; the latter
is henceforth abbreviated as 16-ft PPT. This document is based on the 16-ft PPT method. The literature
background of the method is provided in Annex A.
The 16-ft PPT setup is placed under a large-scale (minimum 3,5 MW) calorimeter in an indoor facility and
is therefore not affected by outdoor weather conditions. The HRR measured during the tests provides an
objective evaluation to the fire performance of specimens. The test setup is further utilized to evaluate
the smoke hazard of the wall systems used in smoke sensitive occupancies from property insurance
[3]
perspective .
v
International Standard ISO 3957:2025(en)
Reaction to fire tests — Parallel panel test method for
wall systems — Measurement of heat release and smoke
production
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 can be evolved during
combustion of test specimens.
Suitable respiratory protection shall be worn by those in the test room when the atmosphere in the
test room becomes unacceptable.
The test procedure involves high temperatures and combustion processes, from ignition to a
fully developed fire. Hazards can arise, e.g. burning or ignition of extraneous objects or clothing.
Operators should use full turn out firefighting gear including self-contained breathing apparatus.
Specimens can be difficult to extinguish, particularly those with combustible content burning inside
metallic facings. At least one charged water hose should be available for all tests.
Specimen collapse can occur. All personnel within the test area should remain at a sufficient distance
from the test specimen to avoid injury in case of specimen collapse.
Combustible or sensitive elements that are not part of the test specimen, such as wires, pipes and
gages close to the setup shall be covered with fire protection blankets.
1 Scope
This document specifies a large-scale fire test method for measuring the heat release rate (HRR) and the
smoke-production rate (SPR) of wall systems. The fire scenario covered in this document is representative of
severe fires originating in near wall or corner locations of an exterior or interior wall construction. A severe
fire scenario is defined that imparts a heat flux on the order of 100 kW/m to the wall systems. These include
exterior fire scenarios such as dumpster, balcony storage fires, and vehicle fires originating outside buildings.
Fires caused by combustible storage inside unsprinklered or inadequately sprinklered occupancies, such as
warehouse and manufacturing occupancies, represent a few examples of severe interior fires.
This document measures the HRR and SPR in accordance with ISO 24473. This document also provides
guidelines for
...
FINAL DRAFT
International
Standard
ISO/FDIS 3957
ISO/TC 92/SC 1
Reaction to fire tests — Parallel
Secretariat: BSI
panel test method for wall systems
Voting begins on:
— Measurement of heat release and
2025-04-03
smoke production
Voting terminates on:
2025-05-29
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 3957:2025(en) © ISO 2025
FINAL DRAFT
ISO/FDIS 3957:2025(en)
International
Standard
ISO/FDIS 3957
ISO/TC 92/SC 1
Reaction to fire tests — Parallel
Secretariat: BSI
panel test method for wall systems
Voting begins on:
— Measurement of heat release and
smoke production
Voting terminates on:
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland Reference number
ISO/FDIS 3957:2025(en) © ISO 2025
ii
ISO/FDIS 3957:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 2
5 Principle . 3
6 Test facility and instrumentation section . 4
7 Apparatus . 4
7.1 General .4
7.2 Metal frames .5
7.3 Sand burner and fuel supply.6
7.4 Weighing platform (Optional) .9
7.5 Assembly preparation .9
7.6 Instrumentation and videography .10
7.7 Data recording and processing .10
8 Calibration .11
8.1 Gas analyser system .11
8.2 Propane sand burner calibration .11
8.3 Heat flux exposure to parallel walls . 12
8.4 Smoke measurement system . 13
8.5 System response . 13
8.6 Weighing platform (optional) . . 13
9 Test procedure and settings .13
10 Calculations and analysis . 14
11 Test report . 14
Annex A (informative) Literature background and performance guidance .16
Annex B (informative) Calorimeter design . 19
Annex C (informative) Propane burner calibrations .23
Annex D (informative) Repeatability .27
Bibliography .36
iii
ISO/FDIS 3957:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 92, Fire safety, Subcommittee SC 1, Fire
initiation and growth.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
ISO/FDIS 3957:2025(en)
Introduction
This large-scale fire test standard is developed for the purpose of measuring the heat release rate (HRR) and
the smoke-production rate (SPR) of exterior and interior wall systems, exposed under severe fire scenarios
using a parallel panel setup. Severe fire exposure to an exterior wall system can be either caused by spill
plumes from a window, such as in a post-flashover compartment fire, or an exterior fire source such as in a
dumpster, vehicle, or balcony storage. Some extreme scenarios for an exterior fire include city conflagration
(e.g. after an earthquake) or wildland-urban-interface (WUI) fires. Severe interior wall fires can be caused
by combustible storage located inside a facility, such as warehouse and manufacturing occupancies, close
to the corners of wall system. A common factor of such fire scenarios is the absence or an inadequacy of the
traditional active fire protection safeguards (e.g. sprinklers) leading to unmitigated heat exposures to wall
systems.
A sufficiently high heat flux is required to simulate such fire exposures ― a high heat flux can reveal the
flammability of the encapsulated materials used in the wall systems, as well as the vulnerabilities of facers,
[1]
joints and other components. Literature shows that severe fire exposure to wall systems is in the order
of 100 kW/m . For this purpose, three large-scale fire tests are known to simulate realistically severe fire
exposures of about 100 kW/m , and are used to evaluate the performance of both exterior and interior wall
[2]to[5]
systems . These three large-scale fire tests include the 7,6 m (25-ft) high corner fire test, 15 m (50-ft)
high corner fire test, and 4,9 m (16-ft) high parallel panel test of the ANSI/FM 4880 standard; the latter
is henceforth abbreviated as 16-ft PPT. This document is based on the 16-ft PPT method. The literature
background of the method is provided in Annex A.
The 16-ft PPT setup is placed under a large-scale (minimum 3,5 MW) calorimeter in an indoor facility and
is therefore not affected by outdoor weather conditions. The HRR measured during the tests provides an
objective evaluation to the fire performance of specimens. The test setup is further utilized to evaluate
the smoke hazard of the wall systems used in smoke sensitive occupancies from property insurance
[3]
perspective .
v
FINAL DRAFT International Standard ISO/FDIS 3957:2025(en)
Reaction to fire tests — Parallel panel test method for
wall systems — Measurement of heat release and smoke
production
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 can be evolved during
combustion of test specimens.
Suitable respiratory protection shall be worn by those in the test room when the atmosphere in the
test room becomes unacceptable.
The test procedure involves high temperatures and combustion processes, from ignition to a
fully developed fire. Hazards can arise, e.g. burning or ignition of extraneous objects or clothing.
Operators should use full turn out firefighting gear including self-contained breathing apparatus.
Specimens can be d
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ISO/TC 92/SC 1/WG 7
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Date: 2025-01-30
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Secretariat: BSI
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Reaction to fire tests — Parallel panel test method for wall systems
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— Measurement of heat release and smoke production
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ISO/FDIS 3957:2025(en)
Formatted: Font: Bold
Formatted: HeaderCentered
Commented [eXtyles1]: The reference "ISO 2025" is to a
withdrawn standard
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
Formatted: Default Paragraph Font
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO Formatted: Default Paragraph Font
at the address below or ISO’s member body in the country of the requester.
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Formatted: French (France)
Formatted: French (France)
Fax: +41 22 749 09 47
EmailE-mail: copyright@iso.org
Formatted: French (France)
Website: www.iso.orgwww.iso.org
Formatted: zzCopyright address, Adjust space between
Latin and Asian text, Adjust space between Asian text
Published in Switzerland
and numbers
Formatted: Font: 11 pt
Formatted: FooterPageRomanNumber, Space Before:
0 pt, Line spacing: single
ii © ISO #### 2025 – All rights reserved
ii
ISO/FDIS 3957:2025(en)
Formatted: Font: 11 pt, Bold, Font color: Auto
Formatted: Font: Bold
Formatted: HeaderCentered, Left
Contents
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
Foreword . vi
Introduction . vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 3
5 Principle . 3
6 Test facility and instrumentation section . 4
7 Apparatus . 4
7.1 General. 4
7.2 Metal frames . 5
7.3 Sand burner and fuel supply . 7
7.4 Weighing platform (Optional) . 9
7.5 Assembly preparation . 9
7.6 Instrumentation and videography . 10
7.7 Data recording and processing . 11
8 Calibration . 11
8.1 Gas analyser system . 11
8.2 Propane sand burner calibration. 11
8.3 Heat flux exposure to parallel walls . 12
8.4 Smoke measurement system . 13
8.5 System response . 13
8.6 Weighing platform (optional) . 13
9 Test procedure and settings . 14
10 Calculations and analysis . 14
11 Test report . 15
Annex A (informative) Literature background and performance guidance . 16
Annex B (informative) Calorimeter design . 19
Annex C (informative) Propane burner calibrations . 23
Annex D (informative) Repeatability . 27
Bibliography . 38
Foreword . v
Introduction . vi
Formatted: Font: 10 pt
1 Scope . 1
Formatted: Font: 10 pt
2 Normative references . 1
Formatted: Font: 10 pt
3 Terms and definitions . 2
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4 Symbols . 3
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5 Principle . 4
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6 Test facility and instrumentation section . 5
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© ISO 2025 – All rights reserved
iii
ISO/FDIS 3957:2025(en)
Formatted: Font: Bold
Formatted: HeaderCentered
7 Apparatus . 5
7.1 General. 5
7.2 Metal frames . 6
7.3 Sand burner and fuel supply . 8
7.4 Weighing platform (Optional) . 10
7.5 Assembly preparation . 10
7.6 Instrumentation and videography . 11
7.7 Data recording and processing . 11
8 Calibration . 12
8.1 Gas analyser system . 12
8.2 Propane sand burner calibration. 12
8.3 Heat flux exposure to parallel walls . 13
8.4 Smoke measurement system . 14
8.5 System response . 14
8.6 Weighing platform (Optional) . 14
9 Test procedure and settings . 14
10 Calculations and analysis . 15
11 Test report . 15
Annex A . 17
A.1 Literature background . 17
A.2 Performance guidance rationale . 17
A.3 Heat release rate and smoke production thresholds . 18
Annex B . 19
B.1 Design examples . 19
B.2 Calorimetry instrumentation description . 20
B.2.1 Gas sampling probes . 20
B.2.2 Multi-gas analyser system . 21
B.2.3 Gas thermocouples . 21
B.2.4 Gas velocity probes . 21
B.2.5 Absolute pressure transducer . 22
B.2.6 Smoke measurement section. 22
B.3 Vertical entrainment velocity.
...
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