prEN IEC 60695-8-1:2026

SLOVENSKI STANDARD
01-september-2026
Preskušanje požarne ogroženosti - 8-1. del: Oddajanje toplote - Splošno navodilo
Fire hazard testing - Part 8-1: Heat release - General guidance
Prüfungen zur Beurteilung der Brandgefahr - Teil 8-1: Wärmefreisetzung - Allgemeiner
Leitfaden
Essais relatifs aux risques du feu - Partie 8-1: Dégagement de chaleur - Guide général
Ta slovenski standard je istoveten z: prEN IEC 60695-8-1:2026
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.

89/1665/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 60695-8-1 ED4
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2026-07-31 2026-10-23
SUPERSEDES DOCUMENTS:
89/1653/CD, 89/1663/CC
IEC TC 89 : FIRE HAZARD TESTING
SECRETARIAT: SECRETARY:
Germany Mr Bernd Komanschek
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):

TC 10,TC 14,TC 20,SC 22F,SC 23A,TC 46,TC
61,SC 86A,TC 99,TC 104,TC 108,TC 112,SC
121A,ACOS
ASPECTS CONCERNED:
Safety
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TITLE:
Fire hazard testing - Part 8-1: Heat release - General guidance

PROPOSED STABILITY DATE: 2029
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CONTENTS
CONTENTS . 3
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Principles of determining heat release . 8
4.1 Heat release of complete combustion measured by the oxygen bomb
calorimeter . 8
4.2 Heat release of incomplete combustion . 9
4.2.1 Measurement techniques . 9
4.2.2 Heat release by oxygen consumption. 9
4.2.3 Heat release by carbon dioxide generation . 10
4.2.4 Heat release by increase of gas temperature . 10
5 Parameters used to report heat release data . 12
5.1 Heat of combustion (gross and net) . 12
5.2 Heat release rate (HRR) . 12
5.3 Heat release (HR) . 13
5.4 Heat release rate per unit area (HRR*) . 13
5.5 Total heat release . 14
5.6 Peak heat release rate . 14
5.7 Time to peak heat release rate . 14
5.8 Effective heat of combustion . 14
5.8.1 Measurement and calculation . 14
5.8.2 Examples . 15
5.9 FIGRA index . 15
5.10 ARHE and MARHE . 17
6 Considerations for the selection of test methods . 18
6.1 Ignition sources . 18
6.2 Type of test specimen . 18
6.3 Choice of conditions . 18
6.4 Test apparatus . 18
6.4.1 General . 18
6.4.2 Small-scale fire test apparatus. 19
6.4.3 Intermediate and large-scale fire test apparatus . 19
6.4.4 Comparison between small-scale and intermediate/large-scale fire test
methods . 19
6.5 Choice of fire tests . 19
7 Relevance of heat release data . 19
7.1 Contribution to fire hazard. 19
7.2 Secondary ignition and flame spread . 20
7.3 Determination of self-propagating fire thresholds . 20
7.4 Probability of reaching flash-over . 20
7.5 Smoke and toxic gas production . 20
7.6 The role of heat release testing in research and development . 20
Bibliography . 21
IEC CDV 60695-8-1 © IEC 2026
Figure 1 – Heat release rate (HRR) curve . 13
Figure 2 – Heat release (HR) curve . 13
Figure 3 – Heat release rate per unit area (HRR*) curve . 14
Figure 4 – Mass loss curve . 15
Figure 5 – FIGRA curve derived from Figure 1 . 16
Figure 6 – Illustrative HRR curve . 16
Figure 7 – FIGRA curve derived from Figure 6 . 17
Figure 8 – ARHE curve derived from Figure 1 . 17
Figure 9 – ARHE curve derived from Figure 6 . 17

Table 1 – Relationship between heat of combustion expressed in units of kJ·g−1 of fuel
−1
burned and kJ·g−1 of oxygen consumed for a variety of fuels ed in units of kJ·g of
−1
fuel burned and kJ·g of oxygen consumed for a variety of fuels . 11
−1
Table 2 – Relationship between heat of combustion expressed in units of kJ·g of fuel
−1
burned and kJ·g of oxygen consumed for a variety of insulating liquids . 12

IEC CDV 60695-8-1 © IEC 2026
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Fire hazard testing -
Part 8-1: Heat release - General guidance

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
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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
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3) IEC Publications have the form of recommendations for international use and are accepted
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies
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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) IEC draws attention to the possibility that the implementation of this document may involve
the use of (a) patent(s). IEC 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,
IEC [had/had not] received notice of (a) patent(s), which may be required to implement this
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IEC CDV 60695-8-1 © IEC 2026
information, which may be obtained from the patent database available at https://patents.iec.ch.
IEC shall not be held responsible for identifying any or all such patent rights.
IEC 60695-8-1 has been prepared by IEC technical committee 89: Fire hazard testing. It is an
International Standard.
It has the status of a basic safety publication in accordance with ISO/IEC Guide 51:2014 [1]
and IEC GUIDE 104:2019 [2].
This forth edition cancels and replaces the second edition published in 2016. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) The status of refernce standards was reviewed and updated;
b) Terms and definitions in ISO 13943:2017 are used;
c) Descriptions of methods of heat release measurement were reviewed and updated.
The text of this standard is based on the following documents:
FDIS Report on voting
89/XXX/FDIS 89/XXX/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
The language used for the development of this International Standard is English.
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 standard is to be used in conjunction with IEC 60695-8-2.
A list of all the parts in the IEC 60695 series, under the general title Fire hazard testing, can be
found on the IEC website.
IEC 60695-8 consists of the following parts:
Part 8-1: Heat release – General guidance
Part 8-2: Heat release – Summary of test methods
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, or
– revised.
IEC CDV 60695-8-1 © IEC 2026
INTRODUCTION
In the design of any 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-
1-10:2016 [3] , IEC 60695-1-11:2014 [4] and EN IEC 60695-1-12:2020 [5] provide guidance on
how this is to be accomplished. Footnote 1: Numbers in square brackets refer to the
bibliography.
Fires involving electrotechnical products can be initiated from external non-electrical sources.
Considerations of this nature are dealt with in an overall risk assessment.
The aim of the IEC 60695 series of standards 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.
Fires are responsible for creating hazards to life and property as a result of the generation of
heat (thermal hazard), toxic and/or corrosive compounds and obscuration of vision due to
smoke. Fire risk increases as the heat released increases, possibly leading to a flash-over fire.
One of the most important measurements in fire testing is the measurement of heat release,
and it is used as an important factor in the determination of fire hazard. It is also used as one
of the parameters in fire safety engineering calculations.
The measured heat release data, together with other fire test data, can be used to reduce the
likelihood of or the effects of fire, even in the event of reasonably foreseeable (mis)use,
malfunction or failure of electrotechnical products.
When a material is heated by some external source, fire effluent can be generated and can
form a mixture with air, which can ignite and initiate a fire. The heat released in the process is
carried away by the fire effluent-air mixture, radiatively lost or transferred back to the material,
to generate further pyrolysis products, thus continuing the process.
Heat may also be transferred to other nearby products, which may ignite, burn, and then release
additional heat and fire effluent.
The rate at which thermal energy is released in a fire is defined as the heat release rate. Heat
release rate is important because of its influence on flame spread and on the initiation of
secondary fires. Other characteristics are also important, such as ignitability, flame spread and
the side-effects of the fire (see the IEC 60695 series of standards).
IEC CDV 60695-8-1 © IEC 2026
1 Scope
This document provides guidance on the measurement of heat release from electrotechnical
products and materials from which they are constructed.
Heat release data can be used as part of fire hazard assessment and in fire safety engineering,
as described in IEC 60695-1-10[1], IEC 60695-1-11[2] and IEC 60695-1-12[3].
This HORIZONTAL BASIC SAFETY PUBLICATION focusing on SAFETY guidance, is primarily
intended for use by Technical Committees in the preparation of SAFETY publications in
accordance with the principles laid down in IEC Guide 104 and ISO/IEC Guide 51[4].
One of the responsibilities of a technical committee is, wherever applicable, to make use of
basic safety publications in the preparation of its 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 Guide 104, The preparation of safety publications and the use of basic safety publications
and group safety publications
IEC 60695-4:2021, Fire hazard testing - Part 4: Terminology concerning fire tests for
electrotechnical products
IEC 60695-8-2, Fire hazard testing – Part 8-2: Heat release – Summary and relevance of test
methods
EN IEC 60695-1-12:2020, Fire hazard testing - Part 1-12: Guidance for assessing the fire
hazard of electrotechnical products - Fire safety engineering
ISO 13943:2017, Fire safety - Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13943:2017 and IEC
60695-4:2021 apply.
– IEC Electropedia: available at http://www.electropedia.org/
– ISO Online browsing platform: available at http://www.iso.org/obp
4 Principles of determining heat release
4.1 Heat release of complete combustion measured by the oxygen bomb calorimeter
The device for measuring heats of complete combustion is called as "oxygen bomb calorimeter".
The "bomb" is a central vessel which has an adiabatic constant volume and is sufficiently strong
to withstand high pressures so that its internal volume remains constant. The bomb is immersed
in a stirred water bath, and the combination of bomb and water bath is the calorimeter. The
calorimeter is also immersed in an outer water bath. During a combustion reaction, the
temperature of the water in the calorimeter and in the outer water bath is continuously monitored
and adjusted by electrical heating to the same value. This is to ensure that there is no net loss
of heat from the calorimeter to its surroundings, i.e. to ensure that the calorimeter is adiabatic.
IEC CDV 60695-8-1 © IEC 2026
To carry out a measurement, a known mass of sample is placed inside the bomb in contact with
an electrical ignition wire. The bomb is filled with oxygen under pressure, sealed and allowed
to attain thermal equilibrium. The sample is then ignited using a measured input of energy.
Sample undergoes complete combustion since it takes place in a confined environment with an
excess of high pressure oxygen. The heat released is calculated from the known heat capacity
of the calorimeter and the rise of temperature which occurs as a result of the combustion
reaction.
The experiment gives the heat released at constant volume, i.e. the change in internal energy,
ΔU. The gross heat of combustion is the enthalpy change, ΔH, where:
𝛥𝐻=𝛥𝑈+𝛥(𝑃𝑉)
where Δ(PV) is calculated using the ideal gas law;
𝛥(𝑃𝑉)=𝛥(𝑛𝑅𝑇)
NOTE Bomb calorimeter measurement of the heat of combustion of building products is described in ISO 1716:2018
[6].
4.2 Heat release of incomplete combustion
4.2.1 Measurement techniques
Combustion in fires, which usually occur in air and at atmospheric pressure, is almost always
incomplete and therefore the heat released will be less than the combined heats of combustion
of the materials involved.
The heat released can be determined indirectly using one of the following techniques:
a) oxygen consumption;
b) carbon dioxide generation;
c) gas temperature increase.
4.2.2 Heat release by oxygen consumption
For a large number of organic fuels, an approximately constant amount of heat is released per
−1
unit of oxygen consumed [7], [8]. The average value for this constant is 13,1 kJ·g of oxygen
and this value is widely used for practical applications both in small-scale and large-scale fire
testing. This relationship implies that it is sufficient to measure the oxygen consumed in a
combustion system, and the mass flow rate in the exhaust duct in order to determine heat
release.
Table 1 lists some net heat of combustion values [8]. With the exception of three materials:
ethene, ethyne and poly oxymethylene, all the calculated heats of combustion per gram of
oxygen consumed lie between 12,5 kJ and 13,6 kJ. The values in Table 1 are calculated
assuming complete combustion. However, Huggett [8] does discuss the effects of possible
incomplete combustion and calculates values of net heat of combustion ΔH for several such
c
cases. For example, in the case of cellulose burning to give a 9:1 ratio of CO to CO:
-1
(C H O )+5,7 O → 5,4 CO + 0,6 CO + 5 H O ΔHc = -13,37 kJ.g of O
6 10 5 2 2 2 2
or burning to give an appreciable amount of carbonaceous char:
-1
(C H O )+3 O → 3 CO + 3 C + 5 H O ΔHc = -13,91 kJ.g of O
6 10 5 2 2 2 2
IEC CDV 60695-8-1 © IEC 2026
compared with complete combustion:
-1
(C H O )+6 O → 6 CO + 5 H O ΔHc = -13,59 kJ.g of O
6 10 5 2 2 2 2
Huggett discusses several other examples and concludes that the assumption of a constant
heat release per unit of oxygen consumed will be sufficiently accurate for most applications.
If the correct value of ΔH per gram of O consumed is known for a particular material then this
c 2
shall be used instead of the approximate value.
Table 2 lists some heat of combustion values for insulating liquids.
There is a variety of fire tests that use the oxygen consumption method. They vary from the
micro-scale, e.g. ASTM D 7309 [9], to the large-scale, e.g. EN 50289-4-11:2002 [10].
Heat release fire tests that are of relevance to the testing of electrotechnical products are
described in IEC 60695-8-2.
4.2.3 Heat release by carbon dioxide generation
This technique is based on the concept that the energy released in a combustion reaction is
approximately proportional to the amount of carbon dioxide generated, provided that
combustion is complete or nearly complete (i.e. with very small CO/CO ratio). The average
−1
value for the proportionality constant is 13,3 kJ·g of carbon dioxide generated. If a more
accurate value is known for the material or product, it shall be used in calculating heat release.
In general, heat release values determined by carbon dioxide generation agree well with heat
release rate values determined by oxygen consumption.
4.2.4 Heat release by increase of gas temperature
The gas temperature technique is based on the assumptions that there are no heat losses and
that all the heat generated by the fire is used to increase the temperature of the hot flowing
mixture of air and fire effluent, and that their temperatures can be determined downstream from
the flaming zone. If the heat losses, mainly from thermal radiation, are negligible, then the gas
temperature rise technique (also called the thermopile technique) represents the same heat
release value as the oxygen consumption or the carbon dioxide generation method. The heat
release is determined by measuring the increase in the temperature of the gases, at the
thermopile, with respect to a reference temperature, generally the ambient temperature. This is
converted to heat release by means of measurements of the total flow
...