IEC TS 60695-2-21:2023

IEC TS 60695-2-21
®

Edition 1.0 2023-06
TECHNICAL
SPECIFICATION

colour
inside


Fire hazard testing –
Part 2-21: Glowing/hot-wire based test methods – Fire containment test on
finished units

IEC TS 60695-2-21:2023-06(en)

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IEC TS 60695-2-21
®

Edition 1.0 2023-06
TECHNICAL
SPECIFICATION
colour
inside
Fire hazard testing –
Part 2-21: Glowing/hot-wire based test methods – Fire containment test on
finished units
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS  13.220.40 ISBN 978-2-8322-7122-3
 Warning! Make sure that you obtained this publication from an authorized distributor.
® Registered trademark of the International Electrotechnical Commission

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– 2 – IEC TS 60695-2-21:2023  IEC 2023
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Test specimen . 9
4.1 General . 9
4.2 Verification of potential ignition sources . 9
4.3 Test conditions . 10
5 Test apparatus . 10
5.1 Nickel-Chromium wire (NiCr wire) . 10
5.2 Test circuit . 10
5.3 Connections . 10
5.4 Cheesecloth . 10
5.5 Test chamber . 10
5.6 Timing device . 11
6 Verification of the NiCr wire . 11
7 Conditioning . 11
7.1 Conditioning of the test specimen . 11
7.2 Conditioning of the cheesecloth . 11
7.3 Testing condition . 11
8 Test procedure . 11
8.1 Flow chart . 11
8.2 Identification of potential ignition sources . 13
8.3 Factors affecting test . 14
8.4 Application of NiCr wire. 14
8.5 Selection of NiCr wire application methodology . 15
8.6 Potential ignition source verification . 16
8.7 Test specimen fire containment verification . 17
9 Observations and measurements . 18
9.1 Initial observations . 18
9.2 Test observations . 18
10 Evaluation of test results . 18
11 Test report . 19
12 Information to be given in the relevant product standard . 19
Annex A (normative) Interpretations of the location of the cylindrical volume . 20
Annex B (normative) NiCr wire application methods – Internal coil winding method . 21
B.1 General . 21
B.2 Insulating material cavity preparation . 21
B.3 NiCr wire coil preparation . 21
Annex C (normative) NiCr wire application methods – External winding method . 24
C.1 General . 24
C.2 Insulated connections winding method . 24
C.3 Non-insulated connections winding method . 25
C.4 Examples of electrical connections applying the external winding method . 26

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IEC TS 60695-2-21:2023  IEC 2023 – 3 –
C.4.1 General . 26
C.4.2 Insulated terminals providing mechanical support function . 26
C.4.3 Insulated terminals with one side not accessible . 26
Annex D (informative) Examples of supply wires fixation methodologies . 28
D.1 General . 28
D.2 Fixation over existing electrical connection supply harness . 28
D.3 Fixation over surrounding parts . 28
Bibliography . 30

Figure 1 – Test procedure flow-chart. 12
Figure 2 – Insulating material cavity cross sectional dimensions . 16
Figure 3 – NiCr wire application methodology selection flow-chart . 16
Figure A.1 – Examples of the location of the cylindrical volume . 20
Figure B.1 – Winding tool . 22
Figure B.2 – Example 1 of NiCr wire coil application . 23
Figure B.3 – Example 2 of NiCr wire coil application . 23
Figure B.4 – Example 3 of NiCr wire coil application . 23
Figure C.1 – Single connection insulating material external winding – Side View . 24
Figure C.2 – Single connection insulating material external winding – Front view . 25
Figure C.3 – Example of non-insulated single terminal electrical connection . 26
Figure C.4 – Example of insulated terminals providing mechanical support function. 26
Figure C.5 – Example of insulated terminal with one side not accessible . 27
Figure D.1 – Fixation over existing harness by stripe . 28
Figure D.2 – Fixation over surrounding parts by adhesive tape – Side view . 29
Figure D.3 – Fixation over surrounding parts by adhesive tape – Top view . 29

Table B.1 – Drill bit and winding tool dimensions . 22

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– 4 – IEC TS 60695-2-21:2023  IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

FIRE HAZARD TESTING –

Part 2-21: Glowing/hot-wire based test methods –
Fire containment test on finished units

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
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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
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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.
IEC TS 60695-2-21 has been prepared by IEC technical committee 89: Fire hazard testing. It is
a Technical Specification.
The text of this Technical Specification is based on the following documents:
Draft Report on voting
89/1554/DTS 89/1561A/RVDTS

Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Specification is English.

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IEC TS 60695-2-21:2023  IEC 2023 – 5 –
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
This publication has the status of a Technical Specification in accordance with IEC Guide 104
and ISO/IEC Guide 51.
NOTE The following print types are used:
• terms defined in Clause 3: in bold type.
A list of all parts in the IEC 60695 series, published under the general title Fire hazard testing,
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The "colour inside" logo on the cover page of this document indicates that it
contains colours which are considered to be useful for the correct understanding of its
contents. Users should therefore print this document using a colour printer.

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– 6 – IEC TS 60695-2-21:2023  IEC 2023
INTRODUCTION
Fires might create hazards to life and property as a result of the generation of heat (emission
of heat on fire hazard), and also as a result of the production of toxic effluent, corrosive effluent
and smoke (fire effluents on the fire hazard). Fires start with ignition and then can grow, leading
in some cases to flash-over and a fully developed fire. Resistance to ignition is therefore one
of the most important parameters of a material to be considered in the assessment of a fire
hazard.
Most current fire hazard assessment techniques evaluate the resistance to ignition
characteristics of a single material or component. These assessment techniques are able to
drive the preselection and validation of materials and components but are not able to evaluate
the possible interaction of materials or components in a complex environment such as in a
finished unit, once a fire event is initiated.
In a fault condition, a finished unit might be subject to the overheating of electrical connections
and contacts. Such overheating can be caused by corrosion, poor crimp connections, incorrect
assembly, erosion of contact surfaces, or mechanical fatigue. Insulating materials that are
overheated can ignite and cause fire.
It is difficult to simulate the actual conditions of potential faults in finished units; therefore all
possible fire hazards should be taken into account at the design stage and subsequently during
the preselection of materials and components.
This fire containment test has been developed to verify if a finished unit is able to contain an
internal fire event, generated by combustible parts ignited by a simulated overheated electrical
connection.

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IEC TS 60695-2-21:2023  IEC 2023 – 7 –
FIRE HAZARD TESTING –

Part 2-21: Glowing/hot-wire based test methods –
Fire containment test on finished units



1 Scope
This part of IEC 60695, which is a Technical Specification, specifies a fire containment test
method for finished units. It is intended to verify the capability of containing of a fire event
generated by an effective ignition source inside a finished unit.
Unless otherwise specified by the relevant product standard, determination of the fire
containment described in this document does not apply to any of the following:
• A single electrical component;
• A single electrical component when incorporated into a finished unit;
• Electrical installation products such as distribution boards, circuit protection devices,
switchgear, controlgear, cable management system and electrical accessories (wiring
devices).
The test method described in this document does not apply to the following electrical
connections:
• Low-power electrical connections contained in finished units, where the maximum power
through the connection does not exceed 15 W.
• Soldered and welded electrical connections are exempted from the evaluations of this
document.
This document is intended to be used for evaluating the capability of fire containment of
finished units, during the selection of finished units and in the design of finished units.
The requirements, test method or test conditions of this document 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 62368-1:2018, Audio/video, information and communication technology equipment –
Part 1: Safety requirements
ISO 13943:2017, Fire safety – Vocabulary

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– 8 – IEC TS 60695-2-21:2023  IEC 2023
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
cheesecloth
2
bleached cotton cloth of approximately 40 g/m
[SOURCE: IEC 62368-1:2018, 3.3.6.2, modified – Deleted the Note to entry]
3.2
draught-free environment
space in which the results of experiments are not significantly affected by the local air speed
Note 1 to entry: A qualitative example is a space in which a wax candle flame remains essentially undisturbed.
–¹ –¹
Quantitative examples are small-scale fire tests in which a maximum air speed of 0,1 m-s or 0,2 m-s is sometimes
specified.
[SOURCE: ISO 13943:2017, 3.83]
3.3
effective ignition source
potential ignition source that has been proved to be able to initiate combustion of surrounding
insulating material or combustible parts
Note 1 to entry: The proving methodology is defined by the test specified in 8.6.
3.4
enclosure
external casing protecting the electrical and mechanical parts of apparatus
Note 1 to entry: The term excludes cables.
[SOURCE: ISO 13943:2017, 3.93]
3.5
finished unit
complete unit which is designed to stand alone, usable by an end-user and having a direct
function for the end-user
Note 1 to entry: It is intended to be placed on the market and/or taken into service as single unit.
Note 2 to entry: Electrical installation products such as distribution boards, circuit protection devices, switchgear,
controlgear, cable management system and electrical accessories (wiring devices) are not considered to be finished
units.

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IEC TS 60695-2-21:2023  IEC 2023 – 9 –
3.6
fire
process of combustion characterized by the emission of heat and fire effluent and usually
accompanied by smoke, flame or glowing or a combination thereof
Note 1 to entry: In English language the term "fire" is used to designate three concepts, two of which relate to
specific types of self-supporting combustion with different meanings. Of these three, two of them are designated
using two different terms in both French and German.
[SOURCE: ISO 13943:2017, 3.114, modified – The domain has been deleted.]
3.7
flame, noun
rapid, self-sustaining, sub-sonic propagation of combustion in a gaseous medium, usually with
emission of light
[SOURCE: ISO 13943:2017, 3.159]
3.8
ignition
DEPRECATED: sustained ignition
initiation of sustained flame
[SOURCE: ISO 13943:2017, 3.218]
3.9
low-power point
electrical connection where the power dissipated at the connection does not exceed 15 W
Note 1 to entry: To dissipate more than 15 W at an electrical connection, the power delivered to a resistive load via
the electrical connection must exceed 60 W. This is based on the maximum power transfer theorem that shows that
an electrical connection can only dissipate one-fourth of the power delivered to a resistive load when the resistance
of the connection is equal to the resistance of the load.
3.10
non-combustible material
not capable of undergoing combustion (see ISO 13943:2017, 3.55) under specified test
conditions
EXAMPLE According to the test method described in this document, steel, glass, ceramic and concrete are
considered examples of non-combustible materials.
[SOURCE: ISO 13943:2017, 3.282, modified – Added “test]
3.11
potential ignition source
electrical connection where electrical energy can cause ignition
[SOURCE: IEC 62368-1:2018, 3.3.9.1, modified – Deleted “PIS” and “location”]
4 Test specimen
4.1 General
The test specimen is a finished unit.
4.2 Verification of potential ignition sources
Before carrying out any tests on the test specimen, it is necessary to identify electrical
connections and verify if these are potential ignition sources as described in 8.2 to 8.6.

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– 10 – IEC TS 60695-2-21:2023  IEC 2023
4.3 Test conditions
The test conditions shall not be significantly different from those occurring when the finished
unit is operated according to the intended use as specified by the manufacturer, taking into
account 8.3. However, the test specimen shall be de-energized during the test with the factors
identified in 8.3 supplied by an external power source. It is acceptable to have limited
modifications to the test specimen and to the potential ignition source in order to allow access
of the heating wire and the related supply wires. Such modifications should not be expected to
have any significant effect on the test results.
5 Test apparatus
5.1 Nickel-Chromium wire (NiCr wire)
The heating wire shall be a Nickel/Chromium wire (NiCr wire), having a nominal composition
of > 77 % Ni and 20 ± 1 % Cr, having a nominal diameter of 0,81 mm ± 0,05 mm (20 AWG), a
minimum length of 100 mm and a resistance at ambient temperature between 15 °C and 35 °C
of (0,22 ± 0,05) Ω per 100 mm length.
NOTE Nickel/Chromium wire is also known as NiCr8020.
5.2 Test circuit
The NiCr wire is heated by a constant current power supply having minimum output
characteristic of 0 A to 15 A. The circuit shall contain a current measuring device which
indicates a true RMS value having an accuracy of ± 2,5 % or more accurate.
5.3 Connections
Due to the high currents involved, it is essential that all electrical connections for the NiCr wire
are capable of carrying the current without affecting the performance or long-term stability of
the circuit. Connections between the NiCr wire and the supply wires shall be made using
non-insulated straight butt splices, ceramic screw terminals or similar means provided that they
are made of non-combustible material.
5.4 Cheesecloth
Cheesecloth is used to evaluate the possible spread of fire outside of the test specimen during
the test in 8.7.
If not otherwise specified in the relevant product standard, cheesecloth shall be as specified
in 3.1.
NOTE The Project Team is aware of the existence of several different types of ignition indicators on the market.
Product committees are welcome to replace the currently described cheesecloth by other types. Product committees
using different ignition indicators than the described are kindly invited to provide their feedback on the type of ignition
indicator and its general behavior, when used according to this test method, to the Project Team, in order to be taken
into account for the future revisions of this document.
5.5 Test chamber
The test chamber shall provide a draught-free environment and shall be provided with suitable
means allowing the observation of specimen during the test of 8.6 and 8.7 and ensuring to meet
the testing conditions defined in 7.3 at the start of the test. The volume of the test chamber
shall be adequate to contain the test specimen and to ensure that oxygen depletion does not
significantly affect the results.

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IEC TS 60695-2-21:2023  IEC 2023 – 11 –
It is recommended that the test chamber is fitted with an extraction device, such as an exhaust
fan, to remove products of combustion which might be toxic. If fitted, the extraction device shall
be switched off during the test and switched on after the test to remove fire effluents.
NOTE Examples of suitable means allowing the observation of specimen are windows and video-cameras.
5.6 Timing device
The timing device shall have a resolution of 0,1 s or less.
6 Verification of the NiCr wire
For each new spool of NiCr wire, the electrical resistance of 100 mm ± 1 mm NiCr wire cut,
shall be measured at an ambient temperature between 15 °C and 35 °C before connecting it to
the supply wires.
The resistance shall comply with the requirements of 5.1.
7 Conditioning
7.1 Conditioning of the test specimen
Unless otherwise specified in the relevant product standard, the test specimen shall be
conditioned for 24 h in an atmosphere having a temperature between 15 °C and 35 °C and a
relative humidity less than or equal to 75 %.
7.2 Conditioning of the cheesecloth
The cheesecloth shall be conditioned for 24 h in an atmosphere having a temperature between
15 °C and 35 °C and a relative humidity less than or equal to 75 %.
7.3 Testing condition
Tests shall be executed in a test chamber as described in 5.5, having a temperature between
15 °C and 35 °C and a relative humidity less than or equal to 75 % at the start of each test.
Before each test, the test chamber shall be ventilated in order to ensure complete extraction of
any fire effluent produced from previous tests.
NOTE In order to ensure complete extraction, it has been found useful to establish
...