EN IEC 60695-6-2:2018
(Main)Fire hazard testing - Part 6-2: Smoke obscuration - Summary and relevance of test methods
Fire hazard testing - Part 6-2: Smoke obscuration - Summary and relevance of test methods
IEC 60695-6-2:2018 provides a summary of commonly used test methods for the assessment of smoke obscuration. It presents a brief summary of static and dynamic test methods in common use, either as international standards or national or industry standards. It includes special observations on their relevance to electrotechnical products and their materials and to fire scenarios, and gives recommendations on their use. This basic safety publication is primarily intended for use by technical committees in the preparation of standards in accordance with the principles laid down in IEC Guide 104 and ISO/IEC Guide 51. It is not intended for use by manufacturers or certification bodies. It has the status of a basic safety publication in accordance with IEC Guide 104 and ISO/IEC Guide 51. This standard is to be used in conjunction with IEC 60695-6-1. This standard cancels and replaces IEC 60695-6-2 published in 2011. This second edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a) updated introduction; b) updated normative references; c) new text in 4.1; d) deletion of references to IEC 60695-6-30 and -31 (withdrawn) e) updates with respect to ISO 5659-2; f) deletion of references to BS 6853 and CEI 20-37-3 (superseded); g) deletion of references to ISO/TR 5924 (withdrawn); h) updated text with respect to EN 50399; i) updated text with respect to ISO 5660-1; j) addition of new Subclause 7.5 k) deletion of Annex B; l) deletion of Annex E; m) additional bibliographic references. Key words: Fire Hazard, Smoke Obscuration
Prüfungen zur Beurteilung der Brandgefahr - Teil 6-2: Sichtminderung durch Rauch - Zusammenfassung und Anwendbarkeit von Prüfverfahren
Essais relatifs aux risques du feu - Partie 6-2: Opacité des fumées - Résumé et pertinence des méthodes d'essais
IEC 60695-6-2:2018 La présente partie de l’IEC 60695 donne un résumé des méthodes d'essais couramment utilisées pour évaluer l’obscurcissement par la fumée. Elle présente un résumé des méthodes d'essais dynamiques et statiques communément utilisées, aussi bien comme normes internationales que nationales ou en tant que normes industrielles. Elle inclut des observations particulières relatives à leur pertinence par rapport aux produits électrotechniques et leurs matériaux et à des scénarios d’incendie, et donne des recommandations pour leur utilisation. Cette publication fondamentale de sécurité doit être utilisée par les comités d’études pour l’établissement de leurs normes conformément aux principes exposés dans le Guide 104 de l’IEC et dans le Guide ISO/IEC 51. Elle a le statut d’une publication fondamentale de sécurité conformément au Guide IEC 104 et au Guide ISO/IEC 51. Cette norme doit être utilisée conjointement avec l’IEC 60695-6-1. Cette norme annule et remplace l’IEC 60695-6-2 parue en 2011. Cette deuxième édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente: a) mise à jour de l’introduction; b) mise à jour des références normatives; c) nouveau texte au 4.1; d) suppression des références aux IEC 60695-6-30 et -31 (supprimées) e) mises à jour en fonction de l’ISO 5659-2; f) suppression des références à la BS 6853 et la CEI 20-37-3 (remplacées); g) suppression des références à l’ISO/TR 5924 (supprimée); h) mise à jour du texte en fonction de l’EN 50399; i) mise à jour du texte en fonction de l’ISO 5660-1; j) ajout d’un nouveau Paragraphe 7.5 k) suppression de l’Annexe B; l) suppression de l’Annexe E; m) ajout de références bibliographiques. Mots clés: risques du feu, Opacité des fumées
Preskušanje požarne ogroženosti - 6-2. del: Otemnitev dima - Povzetek in relevantnost preskusnih metod (IEC 60695-6-2:2018)
Ta del standarda IEC 60695 vsebuje povzetek običajno uporabljenih preskusnih metod za ocenjevanje otemnitve dima. Podaja kratek povzetek običajnih statičnih in dinamičnih preskusnih metod bodisi kot mednarodne standarde bodisi kot nacionalne ali industrijske standarde. Vključuje posebna opažanja glede njihovega pomena za elektrotehnične izdelke in njihove materiale ter požarne scenarije in podaja priporočila glede njihove uporabe.
To osnovno varnostno publikacijo morajo upoštevati tehnični odbori pri pripravi standardov v skladu z načeli vodil IEC 104 in ISO/IEC 51.
Ena od odgovornosti tehničnega odbora je, da pri pripravi publikacij uporablja osnovne varnostne publikacije (kjer je to primerno). Zahteve, preskusne metode ali preskusni pogoji iz te osnovne varnostne publikacije se ne uporabljajo, razen če so izrecno navedeni ali zajeti v ustreznih publikacijah.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-november-2018
1DGRPHãþD
SIST EN 60695-6-2:2012
Preskušanje požarne ogroženosti - 6-2. del: Otemnitev dima - Povzetek in
relevantnost preskusnih metod (IEC 60695-6-2:2018)
Fire hazard testing - Part 6-2: Smoke obscuration - Summary and relevance of test
methods (IEC 60695-6-2:2018)
Prüfungen zur Beurteilung der Brandgefahr - Teil 6-2: Sichtminderung durch Rauch -
Zusammenfassung und Anwendbarkeit von Prüfverfahren (IEC 60695-6-2:2018)
Essais relatifs aux risques du feu - Partie 6-2: Opacité des fumées - Résumé et
pertinence des méthodes d'essais (IEC 60695-6-2:2018)
Ta slovenski standard je istoveten z: EN IEC 60695-6-2:2018
ICS:
13.220.40 Sposobnost vžiga in Ignitability and burning
obnašanje materialov in behaviour of materials and
proizvodov pri gorenju products
29.020 Elektrotehnika na splošno Electrical engineering in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD EN IEC 60695-6-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2018
ICS 13.220.99; 29.020 Supersedes EN 60695-6-2:2011
English Version
Fire hazard testing - Part 6-2: Smoke obscuration -
Summary and relevance of test methods
(IEC 60695-6-2:2018)
Essais relatifs aux risques du feu - Prüfungen zur Beurteilung der Brandgefahr -
Partie 6-2: Opacité des fumées - Résumé et pertinence des Teil 6-2: Sichtminderung durch Rauch - Zusammenfassung
méthodes d'essais und Anwendbarkeit von Prüfverfahren
(IEC 60695-6-2:2018) (IEC 60695-6-2:2018)
This European Standard was approved by CENELEC on 2018-07-10. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,
Switzerland, Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60695-6-2:2018 E
European foreword
The text of document 89/1399/FDIS, future edition 2 of IEC 60695-6-2, prepared by IEC/TC 89 "Fire
hazard testing" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
The following dates are fixed:
(dop) 2019-04-10
• latest date by which the document has to be
implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2021-07-10
standards conflicting with the
document have to be withdrawn
This document supersedes EN 60695-6-2:2011.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Endorsement notice
The text of the International Standard IEC 60695-6-2:2018 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60695-1-10 NOTE Harmonized as EN 60695-1-10.
IEC 60695-1-11 NOTE Harmonized as EN 60695-1-11.
ISO 5659-2 NOTE Harmonized as EN ISO 5659-2.
IEC 61034-1 NOTE Harmonized as EN 61034-1.
IEC 61034-2 NOTE Harmonized as EN 61034-2.
IEC 60332-3-10 NOTE Harmonized as EN 60332-3-10.
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1 Where an International Publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here:
www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60695-6-1 - Fire hazard testing - Part 6-1: Smoke EN 60695-6-1 -
obscuration - General guidance
ISO/IEC Guide 51 - Safety aspects - Guidelines for their - -
inclusion in standards
IEC Guide 104 - The preparation of safety publications and - -
the use of basic safety publications and
group safety publications
ISO 5660-1 2015 Reaction-to-fire tests - Heat release, - -
smoke production and mass loss rate -
Part-1: Heat release rate (cone calorimeter
method) and smoke production rate
(dynamic measurement)
ISO 13943 2008 Fire safety - Vocabulary EN ISO 13943 2010
ISO 19706 2011 Guidelines for assessing the fire threat to - -
people
IEC 60695-6-2 ®
Edition 2.0 2018-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
BASIC SAFETY PUBLICATION
PUBLICATION FONDAMENTALE DE SÉCURITÉ
Fire hazard testing –
Part 6-2: Smoke obscuration – Summary and relevance of test methods
Essais relatifs aux risques du feu –
Partie 6-2: Opacité des fumées – Résumé et pertinence des méthodes d'essais
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 13.220.99; 29.020 ISBN 978-2-8322-5780-7
– 2 – IEC 60695-6-2:2018 © IEC 2018
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Types of of test method . 11
4.1 General . 11
4.2 The physical fire model . 11
4.3 Static test methods . 12
4.4 Dynamic test methods . 12
5 Types of test specimen . 14
6 Published static test methods . 14
6.1 General . 14
6.2 Determination of smoke opacity in a 0,51 m chamber . 14
6.2.1 Standards which use a vertically oriented test specimen . 14
6.2.2 Standard which uses a horizontally oriented test specimen . 16
6.3 Determination of smoke density in a 27 m smoke chamber . 18
6.3.1 Standards . 18
6.3.2 Purpose and principle . 18
6.3.3 Test specimen . 18
6.3.4 Method . 18
6.3.5 Repeatability and reproducibility . 19
6.3.6 Relevance of test data and special observations. 19
7 Published dynamic test methods . 19
7.1 General . 19
7.2 Determination of smoke density generated by electric cables mounted on a
horizontal ladder . 20
7.2.1 Standards . 20
7.2.2 Purpose and principle . 20
7.2.3 Test specimen . 20
7.2.4 Method . 20
7.2.5 Repeatability and reproducibility . 20
7.2.6 Relevance of test data and special observations. 20
7.3 Determination of smoke generated by electrical cables mounted on a vertical
ladder . 20
7.3.1 ASTM and UL standards . 20
7.3.2 European standard . 21
7.4 Determination of smoke using a cone calorimeter . 23
7.4.1 Standards . 23
7.4.2 Purpose and principle . 23
7.4.3 Test specimen . 23
7.4.4 Method . 23
7.4.5 Repeatability and reproducibility . 24
7.4.6 Relevance of test data and special observations. 24
7.5 Determination of smoke generated by discrete (non-continuous) products . 24
7.5.1 Standards . 24
IEC 60695-6-2:2018 © IEC 2018 – 3 –
7.5.2 Purpose and principle . 24
7.5.3 Test specimen . 25
7.5.4 Method . 25
7.5.5 Repeatability and reproducibility . 25
7.5.6 Relevance of test data and special observations. 25
8 Overview of methods and relevance of data . 25
Annex A (informative) Repeatability and reproducibility data – NBS smoke chamber –
Interlaboratory tests from the French standard NF C20-902-1 and NF C20-902-2 . 28
Annex B (informative) Repeatability and reproducibility data – "Three metre cube"
smoke chamber – French interlaboratory tests according to IEC 61034-2 . 29
Annex C (informative) Repeatability and reproducibility data – NFPA 262 . 30
Bibliography . 31
Table 1 – Characteristics of fire stages (ISO 19706:2011) . 13
Table 2 – Overview of smoke test methods . 26
Table A.1 – Measurement of D . 28
m
Table B.1 – Measurement of transmission expressed as a percentage . 29
Table C.1 – Measurements of Peak Optical Density . 30
Table C.2 – Measurements of Average Optical Density . 30
– 4 – IEC 60695-6-2:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIRE HAZARD TESTING –
Part 6-2: Smoke obscuration –
Summary and relevance of test methods
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60695-6-2 has been prepared by IEC technical committee 89: Fire
hazard testing.
This standard cancels and replaces IEC 60695-6-2 published in 2011. This second edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) updated introduction;
b) updated normative references;
c) new text in 4.1;
d) deletion of references to IEC 60695-6-30 and -31 (withdrawn)
e) updates with respect to ISO 5659-2;
IEC 60695-6-2:2018 © IEC 2018 – 5 –
f) deletion of references to BS 6853 and CEI 20-37-3 (superseded);
g) deletion of references to ISO/TR 5924 (withdrawn);
h) updated text with respect to EN 50399;
i) updated text with respect to ISO 5660-1;
j) addition of new Subclause 7.5
k) deletion of Annex B;
l) deletion of Annex E;
m) additional bibliographic references.
This standard is to be used in conjunction with IEC 60695-6-1.
It has the status of a basic safety publication in accordance with IEC Guide 104 and
ISO/IEC Guide 51.
The text of this standard is based on the following documents:
FDIS Report on voting
89/1399/FDIS 89/1405/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 60695 series, under the general title Fire hazard testing, can be
found on the IEC website.
Part 6 consists of the following parts:
Part 6-1: Smoke obscuration – General guidance
Part 6-2: Smoke obscuration – Summary and relevance of test methods
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC 60695-6-2:2018 © IEC 2018
INTRODUCTION
In the design of an electrotechnical product the risk of fire and the potential hazards
associated with fire need to be considered. In this respect the objective of component, circuit
and equipment design, as well as the choice of materials, is to reduce the risk of fire to a
tolerable level even in the event of reasonably foreseeable (mis)use, malfunction or failure.
IEC 60695-1-10 [1] , IEC 60695-1-11 [2], and IEC 60695-1-12 [3] provide guidance on how
this is to be accomplished.
Fires involving electrotechnical products can also be initiated from external non-electrical
sources. Considerations of this nature are dealt with in an overall fire hazard assessment.
The aim of the IEC 60695 series is to save lives and property by reducing the number of fires
or reducing the consequences of the fire. This can be accomplished by:
• trying to prevent ignition caused by an electrically energised component part and, in the
event of ignition, to confine any resulting fire within the bounds of the enclosure of the
electrotechnical product.
• trying to minimise flame spread beyond the product’s enclosure and to minimise the
harmful effects of fire effluents including heat, smoke, and toxic or corrosive combustion
products.
One of the contributing hazards is the release of smoke, which may cause loss of vision
and/or disorientation which could impede escape from the building, or fire fighting.
This part of IEC 60695 describes smoke test methods in common use to assess the smoke
release from electrotechnical products, or from materials used in electrotechnical products. It
gives guidance to product committees wishing to incorporate test methods for smoke
obscuration in product standards.
___________
Numbers in square brackets refer to the bibliography.
IEC 60695-6-2:2018 © IEC 2018 – 7 –
FIRE HAZARD TESTING –
Part 6-2: Smoke obscuration –
Summary and relevance of test methods
1 Scope
This part of IEC 60695 provides a summary of commonly used test methods for the
assessment of smoke obscuration. It presents a brief summary of static and dynamic test
methods in common use, either as international standards or national or industry standards. It
includes special observations on their relevance to electrotechnical products and their
materials and to fire scenarios, and gives recommendations on their use.
This basic safety publication shall be used by technical committees in the preparation of
standards in accordance with the principles laid down in IEC Guide 104 and
ISO/IEC Guide 51.
One of the responsibilities of a technical committee is, wherever applicable, to make use of
basic safety publications in the preparation of its publications. The requirements, test methods
or test conditions of this basic safety publication will not apply unless specifically referred to
or included in the relevant publications.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60695-6-1, Fire hazard testing – Part 6-1: Smoke obscuration – General guidance
ISO/IEC Guide 51, Safety aspects – Guidelines for their inclusion in standards
IEC GUIDE 104, The preparation of safety publications and the use of basic safety
publications and group safety publications
ISO 5660-1:2015, Reaction-to-fire tests – Heat release, smoke production and mass loss rate
– Part 1: Heat release rate (cone calorimeter method) and smoke production rate (dynamic
measurement)
ISO 13943:2008, Fire safety – Vocabulary
ISO 19706:2011, Guidelines for assessing the fire threat to people
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13943:2008, some
of which are reproduced below for users’ convenience, and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
– 8 – IEC 60695-6-2:2018 © IEC 2018
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
combustion
exothermic reaction of a substance with an oxidising agent
Note 1 to entry: Combustion generally emits fire effluent accompanied by flames and/or glowing.
[SOURCE: ISO 13943:2008, 4.46]
3.2
extinction area of smoke
product of the volume occupied by smoke and the extinction coefficient of the smoke
Note 1 to entry: It is a measure of the amount of smoke, and the typical units are square metres (m ).
[SOURCE: ISO 13943:2008, 4.92]
3.3
extinction coefficient
natural logarithm of the ratio of incident light intensity to transmitted light intensity, per unit
light path length
-1
Note 1 to entry: Typical units are reciprocal metres (m ).
[SOURCE: ISO 13943:2008, 4.93]
3.4
fire
(general) process of combustion characterized by the emission of heat and fire effluent and
usually accompanied by smoke, flame, glowing or a combination thereof
Note 1 to entry: In the English language the term "fire" is used to designate three concepts, two of which, fire
(3.5) and fire (3.6), relate to specific types of self-supporting combustion with different meanings and two of them
are designated using two different terms in both French and German.
[SOURCE: ISO 13943:2008, 4.96]
3.5
fire
(controlled) self-supporting combustion that has been deliberately arranged to provide useful
effects and is limited in its extent in time and space
[SOURCE: ISO 13943:2008, 4.97]
3.6
fire
(uncontrolled) self-supporting combustion that has not been deliberately arranged to provide
useful effects and is not limited in its extent in time and space
[SOURCE: ISO 13943:2008, 4.98]
3.7
fire effluent
totality of gases and aerosols, including suspended particles, created by combustion or
pyrolysis in a fire
IEC 60695-6-2:2018 © IEC 2018 – 9 –
[SOURCE: ISO 13943:2008, definition 4.105]
3.8
fire hazard
physical object or condition with a potential for an undesirable consequence from fire
[SOURCE: ISO 13943:2008, 4.112]
3.9
fire model
fire simulation
calculation method that describes a system or process related to fire development, including
fire dynamics and the effects of fire
[SOURCE: ISO 13943:2008, 4.116]
3.10
fire scenario
qualitative description of the course of a fire with respect to time, identifying key events that
characterise the studied fire and differentiate it from other possible fires
Note 1 to entry: It typically defines the ignition and fire growth processes, the fully developed fire stage, the fire
decay stage, and the environment and systems that impact on the course of the fire.
[SOURCE: ISO 13943:2008, 4.129]
3.11
heat flux
amount of thermal energy emitted, transmitted or received per unit area and per unit time
-2
Note 1 to entry: The typical units are watts per square metre (W × m ).
[SOURCE: ISO 13943:2008, 4.173]
3.12
ignition
sustained ignition (deprecated)
(general) initiation of combustion
[SOURCE: ISO 13943:2008, 4.187]
3.13
ignition
sustained ignition (deprecated)
(flaming combustion) initiation of sustained flame
[SOURCE: ISO 13943:2008, 4.188]
3.14
mass optical density of smoke
optical density of smoke multiplied by a factor, V/(∆m L), where V is the volume of the test
chamber, ∆m is the mass lost from the test specimen, and L is the light path length
2 -1
Note 1 to entry: The typical units are square metres per gram (m × g ).
[SOURCE: ISO 13943:2008, 4.225]
– 10 – IEC 60695-6-2:2018 © IEC 2018
3.15
obscuration by smoke
reduction in the intensity of light due to its passage through smoke
cf. extinction area of smoke (3.2) and specific extinction area of smoke (3.23).
Note 1 to entry: In practice, obscuration by smoke is usually measured as the transmittance, which is normally
expressed as a percentage.
Note 2 to entry: Obscuration by smoke causes a reduction in visibility.
[SOURCE: ISO 13943:2008, 4.242]
3.16
optical density of smoke
measure of the attenuation of a light beam passing through smoke expressed as the logarithm
to the base 10 of the opacity of smoke
cf. specific optical density of smoke (3.25)
Note 1 to entry: The optical density of smoke is dimensionless.
[SOURCE: ISO 13943:2008, 4.244]
3.17
physical fire model
laboratory process, including the apparatus, the environment and the fire test procedure
intended to represent a certain phase of a fire
[SOURCE: ISO 13943:2008, 4.251]
3.18
plenum
area located above false ceilings where heating, ventilating or air-conditioning ducts are
located, as well as communication cables and other utilities
3.19
real-scale fire test
fire test that simulates a given application, taking into account the real scale, the real way the
item is installed and used, and the environment
Note 1 to entry: Such a fire test normally assumes that the products are used in accordance with the conditions
laid down by the specifier and/or in accordance with normal practice.
[SOURCE: ISO 13943:2008, 4.273]
3.20
small-scale fire test
fire test performed on a test specimen of small dimensions
Note 1 to entry: A fire test performed on a test specimen of which the maximum dimension is less than 1 m is
usually called a small-scale fire test.
[SOURCE: ISO 13943:2008, 4.292]
3.21
smoke
visible part of fire effluent
[SOURCE: ISO 13943:2008, 4.293]
IEC 60695-6-2:2018 © IEC 2018 – 11 –
3.22
smoke production rate
amount of smoke produced per unit time in a fire or fire test
Note 1 to entry: It is calculated as the product of the volumetric flow rate of smoke and the extinction coefficient
of the smoke at the point of measurement.
2 -1
Note 2 to entry: The typical units are square metres per second (m × s ).
[SOURCE: ISO 13943:2008, 4.295]
3.23
smoke release rate
see smoke production rate (3.21)
3.24
specific extinction area of smoke
extinction area of smoke produced by a test specimen in a given time period divided by the
mass lost from the test specimen in the same time period
2 -1
Note 1 to entry: The typical units are square metres per gram (m ·g ).
[SOURCE: ISO 13943:2008, 4.301]
3.25
specific optical density of smoke
optical density of smoke multiplied by a geometric factor
Note 1 to entry: The geometric factor is V /(A × L), where V is the volume of the test chamber, A is the area of the
exposed surface of the test specimen, and L is the light path length.
Note 2 to entry: The use of the term “specific” does not denote “per unit mass” but rather denotes a quantity
associated with a particular test apparatus and area of the exposed surface of the test specimen.
Note 3 to entry: The specific optical density of smoke is dimensionless.
[SOURCE: ISO 13943:2008, 4.303]
3.26
visibility
maximum distance at which an object of defined size, brightness and contrast can be seen
and recognized
[SOURCE: ISO 13943:2008, 4.350]
4 Types of of test method
4.1 General
In cases where fire tests are not yet specified, and need to be developed or altered for the
special purpose of an IEC technical committee, this shall be done in liaison with the relevant
IEC technical committee.
The test method(s) selected shall be relevant to the fire scenario of concern.
4.2 The physical fire model
The amount and rate of smoke released from a given material or product is not an inherent
property of that material or product, but is critically dependent on the conditions under which
that material or product is burnt. Decomposition temperature, amount of ventilation and fuel
– 12 – IEC 60695-6-2:2018 © IEC 2018
composition are the main variables which affect the composition of fire effluent, and hence the
amount of smoke and smoke production rate.
It is critical to show that the test conditions defined in a standardised test method (the
physical fire model) are relevant to, and replicate the desired stage of a real fire. ISO has
published a general classification of fire stages in ISO 19706:2011, shown in Table 1. The
important factors affecting smoke production are oxygen concentration and
irradiance/temperature.
4.3 Static test methods
A static smoke test is one in which the smoke generated is allowed to accumulate within the
test chamber. Some recirculation and secondary combustion of smoke particles may occur.
The obscuration by smoke may be affected by deposition, agglomeration, stirring and
progressive oxygen depletion.
4.4 Dynamic test methods
A dynamic smoke test is one in which there is a continuous flow of fire effluent through the
measuring device without recirculation. In this test, the smoke particles generated are not
allowed to accumulate and are dispersed in the controlled air flow through the test apparatus.
Decay of the smoke can occur in a dynamic test, and may involve coagulation of particles
and/or their deposition on cooling.
IEC 60695-6-2:2018 © IEC 2018 – 13 –
Table 1 – Characteristics of fire stages (ISO 19706:2011)
Fire stage Heat flux to Oxygen volume % Fuel/air
Max. temperature °C
[CO] 100×[CO2]
fuel surface equivalence
[CO2] ([CO2]+ [CO])
ratio (plume)
kW/m
Fuel surface Upper layer Entrained Exhausted
v/v % efficiency
1. Non-flaming
a. self-sustaining
d
n.a. 450 to 800 25 to 85 20 20 0,1 to 1 50 to 90
(smouldering)
b. oxidative pyrolysis from
c c
a b
externally applied 300 to 600 20 20 < 1
radiation
c. anaerobic pyrolysis from
b c c
externally applied 100 to 500 0 0 >> 1
radiation
e
d
2. Well-ventilated flaming 0 to 60 350 to 650 50 to 500 ≈ 20 ≈ 20 < 1 < 0,05 > 95
f
3. Under-ventilated flaming
a. small, localized fire,
a
generally in a poorly 0 to 30 300 to 600 50 to 500 15 to 20 5 to 10 > 1 0,2 to 0,4 70 to 80
ventilated compartment
i
g h
b. post-flashover fire 50 to 150 350 to 650 > 600 < 15 < 5 > 1 0,1 to 0,4 70 to 90
a
The upper limit is lower than for well-ventilated flaming combustion of a given combustible.
b
The temperature in the upper layer of the fire room is most likely determined by the source of the externally applied radiation and room geometry.
c
There are few data; but for pyrolysis, this ratio is expected to vary widely depending on the material chemistry and the local ventilation and thermal conditions.
d
The fire’s oxygen consumption is small compared to that in the room or the inflow, the flame tip is below the hot gas upper layer or the upper layer is not yet significantly
vitiated to increase the CO yield significantly, the flames are not truncated by contact with another object, and the burning rate is controlled by the availability of fuel.
e
The ratio may be up to an order of magnitude higher for materials that are fire-resistant. There is no significant increase in this ratio for equivalence ratios up to ≈ 0,75.
Between ≈ 0,75 and 1, some increase in this ratio may occur.
f
The fire’s oxygen demand is limited by the ventilation opening(s); the flames extend into the upper layer.
g
Assumed to be similar to well-ventilated flaming.
h
The plume equivalence ratio has not been measured; the use of a global equivalence ratio is inappropriate.
i
Instances of lower ratios have been measured. Generally, these result from secondary combustion outside the room vent.
– 14 – IEC 60695-6-2:2018 © IEC 2018
5 Types of test specimen
The test specimen may be a manufactured product, a component of a product, a simulated
product (representative of a portion of a manufactured product), a basic material (solid or
liquid), or a composite of materials.
6 Published static test methods
6.1 General
The static test methods reviewed in this clause were selected on the basis that they are
published international, national or industry standards, and are in common usage in the
electrotechnical field. It is not intended to review all possible test methods.
NOTE These summaries are intended as a brief outline of the test methods; however, full information is given in
the published standards.
6.2 Determination of smoke opacity in a 0,51 m chamber
6.2.1 Standards which use a vertically oriented test specimen
6.2.1.1 Standards
Four national standards are based on testing a vertically oriented test specimen in a single
chamber of 0,51 m volume.
NOTE The chamber was developed in the USA by the National Bureau of Standards (now known as the National
Institute of Standards and Technology) and is often referred to as the “NBS chamber”.
These are: ASTM E662 [1], BS 6401 [5], NF C20-902-1 [6] and NF C20-902-2 [7].
6.2.1.2 Purpose and principle
This small-scale fire test is used to assess the opacity of the smoke generated by a vertically
oriented test specimen of material exposed to a specified thermal irradiance, with or without
pilot flames, in a closed chamber 0,51 m in volume. The luminous flux through the smoke is
continuously recorded.
6.2.1.3 Test specimen
The test specimen is a flat piece 76,2 mm × 76,2 mm, with a maximum thickness of 25,4 mm.
6.2.1.4 Method
The method employs an electrical radiant energy source mounted so as to produce a heat flux
of 25 kW/m on a vertically mounted test specimen. Two modes of test are commonly used:
a) non-flaming, where only the radiant energy source is used, or
b) flaming, where a small burner is used in addition to the radiant energy source. This burner
produces a row of pilot flames along the lower edge of the test specimen, which ignite any
combustion products.
A photometric system using polychromatic white light, with a vertical light path is used to
measure the variation in light transmission during the test.
Results are expressed in terms of specific optical density, D , which is calculated using the
S
following equation:
IEC 60695-6-2:2018 © IEC 2018 – 15 –
D = (V / AL) log (I /T )
s 10
where
V is the volume of smoke (i.e. the volume of the chamber);
A is the exposed surface area of the test specimen;
L is the path length of the light used to measure the smoke;
I is the incident luminous flux;
T is the transmitted luminous flux.
D is related to the extinction area of the smoke (S) by the equation:
S
D = S / [A×ln(10) ]
s
i.e.
D = S / [2,303× A]
s
where S is the extinction area of smoke.
NOTE D is used instead of D in NF C20-902-1 & -2 (see A.1).
m S
6.2.1.5 Repeatability and reproducibility
Repeatability and reproducibility have been determined in an interlaboratory trial, based on
the French standards NF C20-902-1 and NF C20-902-2.
The results, presented in accordance with ISO 5725-2 [8], are given in Annex A.
6.2.1.6 Relevance of test data and special observations
Test methods based on the NBS smoke chamber have been in worldwide use since about
1970, primarily for material evaluation purposes. However, these methods have now, in many
cases, been superseded by ISO 5659-2 (see 6.2.2), which overcomes the following significant
limitations of the NBS method:
a) The heat flux is relatively low, and the air supply limited, which means that the method is
only able to replicate conditions found in ISO 19706 fire stages 1 b) and, possibly, 2 (see
Table 1).
b) The test specimen is small, vertically mounted and is essentially flat, which limits the
scope of the method to the evaluation of materials only, and excludes liquids and some
thermoplastics. Test specimens which swell towards the furnace also give problems, as
the incident heat flux experienced by the front of the test specimen increases significantly,
and the pilot flames can be extinguished, rendering the test invalid.
c) The limitations of the low heat flux and test specimen geometry mean that it is difficult to
establish a link between data from the NBS chamber and other fire scenarios.
Further limitations of methods based on the NBS smoke chamber include the following:
d) There is little or no correlation between data from this test, and the behaviour of products
in fires or real-scale fire tests.
e) There are no means of monitoring test specimen mass during the test.
f) The air supply is limited and the test specimen ceases to burn if the oxygen concentration
falls below approximately 14 %.
g) The deposition of smoke on the walls is significant.
h) The repeatability and reproducibility of the method have been studied several times and
found to be very poor (see Annex A), and dependent on the nature of the material under
test. Materials with high flow, excessive swelling or irreproducible ignitability produce less
reliable results.
– 16 – IEC 60695-6-2:2018 © IEC 2018
The method does however offer the useful option to evaluate smoke production from both
flaming and non-flaming combustion, albeit at a low heat flux.
The data generated are not suitable for use as input to fire hazard assessment or for fire
safety engineering.
Overall, this method is not recommended for further development for electrotechnical
products. Neither is it recommended as the basis for regulation or other controls on smoke
release for electrotechnical products, due to the limitations on the physical fire model and test
specimen geometry.
NOTE IEC TR 60695-6-30 and IEC 60695-6-31, which used this test method, were withdrawn at the end of 2015
because of the shortcomings of the test method.
6.2.2 Standard which uses a horizontally oriented test specimen
6.2.2.1 Standard
One International standard, ISO 5659-2 [9], is based on the following method:
6.2.2.2 Purpose and principle
This test is used to assess the opacity of the smoke generated by a horizontally oriented test
specimen of material exposed to a specified thermal irradiance, with or without a pilot flame,
in a closed chamber 0,51 m in volume. The luminous flux through the smoke is continuously
measured and recorded.
NOTE This method uses essentially the same apparatus as described in 6.2.1, with the exception of modifications
to the source of thermal irradiance and test specimen orientation.
6.2.2.3 Test specimen
The test specimen is a flat piece 75 mm × 75 mm with a maximum thickness of 25 mm.
6.2.2.4 Method
This test method employs an electrically heated conical radiant energy source to expose
2 2
horizontally mounted test specimens to an incident flux of 25 kW/m or 50 kW/m . The heat
source consists of electrical windings contained within a truncated steel cone. The exposure
can be in flaming mode or in non-flaming mode, depending on whether or not a pilot flame,
consisting of a small gas burner, is used.
The test chamber is a closed chamber, 0,51 m in volume, and the smoke opacity is assessed
by means of a photometric system, with a white light shining vertically through the chamber.
The photodetector measures the decrease in light transmission due to the accumulation of
smoke.
Test specimens are placed horizontally under the conical radiant heater with a distance of
25 mm between the surface of the test specimen and the lower edge of the heater. For test
specimens which intumesce
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