SIST EN IEC 60068-2-2:2026

SLOVENSKI STANDARD
01-januar-2026
Okoljsko preskušanje - 2-2. del: Preskusi - Preskusi b: Suha vročina (IEC 60068-2-
2:2025)
Environmental testing - Part 2-2: Tests - Test b: Dry heat (IEC 60068-2-2:2025)
Umgebungseinflüsse - Teil 2-2: Prüfverfahren - Prüfung B: Trockene Wärme (IEC 60068
-2-2:2025)
Essais d'environnement - Partie 2-2: Essais - Essai b: Chaleur sèche (IEC 60068-2-
2:2025)
Ta slovenski standard je istoveten z: EN IEC 60068-2-2:2025
ICS:
19.040 Preskušanje v zvezi z Environmental testing
okoljem
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 60068-2-2

NORME EUROPÉENNE
EUROPÄISCHE NORM November 2025
ICS 19.040 Supersedes EN 60068-2-2:2007
English Version
Environmental testing - Part 2-2: Tests - Test B: Dry heat
(IEC 60068-2-2:2025)
Essais d'environnement - Partie 2-2: Essais - Essai B: Umgebungseinflüsse - Teil 2-2: Prüfverfahren - Prüfung B:
Chaleur sèche Trockene Wärme
(IEC 60068-2-2:2025) (IEC 60068-2-2:2025)
This European Standard was approved by CENELEC on 2025-10-28. 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye 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
© 2025 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60068-2-2:2025 E

European foreword
The text of document 104/1108/FDIS, future edition 6 of IEC 60068-2-2, prepared by TC 104
"Environmental conditions, classification and methods of test" was submitted to the IEC-CENELEC
parallel vote and approved by CENELEC as EN IEC 60068-2-2:2025.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2026-11-30
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2028-11-30
document have to be withdrawn
This document supersedes EN 60068-2-2:2007 and all of its amendments and corrigenda (if any).
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.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 60068-2-2:2025 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 standard indicated:
IEC 60068-2-1 NOTE Approved as EN 60068-2-1
IEC 60068-2-14 NOTE Approved as EN IEC 60068-2-14
IEC 60068-3-1 NOTE Approved as EN IEC 60068-3-1
IEC 60068-3-6 NOTE Approved as EN IEC 60068-3-6
IEC 60068-3-7 NOTE Approved as EN IEC 60068-3-7
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.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60068-1 - Environmental testing - Part 1: General EN 60068-1 -
and guidance
IEC 60068-5-2 - Environmental testing - Part 5-2: Guide to EN 60068-5-2 -
drafting of test methods - Terms and
definitions
IEC 60721 series Classification of environmental conditions EN 60721 series

IEC 60068-2-2 ®
Edition 6.0 2025-09
INTERNATIONAL
STANDARD
Environmental testing -
Part 2-2: Tests - Test B: Dry heat
ICS 19.040  ISBN 978-2-8327-0732-6

IEC 60068-2-2:2025-09(en)
IEC 60068-2-2:2025 © IEC 2025
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Symbols . 7
5 Application of tests for non-heat-dissipating specimens versus tests for heat-
dissipating specimens . 7
5.1 General . 7
5.2 Ascertaining high or low air velocity in the test chamber . 8
5.3 Temperature monitoring . 9
5.4 Packaging . 10
5.5 Background . 10
6 Test descriptions . 10
6.1 General . 10
6.2 Severities. 11
6.2.1 General . 11
6.2.2 High conditioning temperature T . 11
B
6.2.3 Exposure time t . 11
6.3 Test Bb: Dry heat for non-heat-dissipating specimens . 11
6.4 Test Bd: Dry heat for heat-dissipating specimens that are energized after
initial temperature stabilization. 13
6.5 Test Be: Dry heat for heat-dissipating specimens that are energized
throughout the test . 14
7 Testing procedure. 15
7.1 General . 15
7.2 Thermal radiation . 15
7.3 Specimen with artificial cooling or heating . 15
7.4 Mounting . 15
7.5 Initial measurements . 16
7.6 Preconditioning . 16
7.7 Conditioning. 16
7.8 Intermediate measurements . 16
7.9 Final temperature ramp . 16
7.10 Recovery . 16
7.11 Final measurements. 17
8 Information to be given in the relevant specification . 17
9 Information to be given in the test report . 18
Annex A (informative) Relationship of suffixes between Test A: Cold and Test B: Dry
heat . 19
Annex B (normative) Nomogram for the correction of the conditioning temperature . 20
B.1 General . 20
B.2 Determination of the corrected high conditioning temperature T . 20
B'
B.2.1 General . 20
B.2.2 Application of the graphical solution method . 20
B.2.3 Application of the numerical solution method . 22
IEC 60068-2-2:2025 © IEC 2025
B.2.4 Conditioning with the corrected conditioning temperature T . 23
B'
B.2.5 Further adjustment of the corrected high conditioning temperature T . 24
B'
B.3 Example of application of the nomogram . 25
B.3.1 Example of test setup and specimen . 25
B.3.2 Graphical solution method . 25
B.3.3 Numerical solution method . 27
Annex C (informative) Advantages and disadvantages of available test procedures for
heat-dissipating specimens . 28
Bibliography . 29

Figure 1 – Examples of temperature profiles of energized heat-dissipating specimens
in test chambers with a) high air velocity and b) low air velocity . 9
Figure 2 – Block diagram of the test procedures and applicable selection criteria of
Test B: Dry heat . 10
Figure 3 – Test Bb: Dry heat for non-heat-dissipating and non-operating specimens . 12
Figure 4 – Test Bb: Dry heat for non-heat-dissipating, operating specimens . 12
Figure 5 – Test Bd: Dry heat for heat-dissipating specimens that are energized after
initial temperature stabilization . 13
Figure 6 – Test Be: Dry heat for heat-dissipating specimens that are required to be
energized throughout the test . 14
Figure B.1 – Nomogram to determine the corrected conditioning temperature T . 21
B'
Figure B.2 – a) Test Bd and b) Test Be with the corrected conditioning temperature T . 23
B'
Figure B.3 – a) Test Bd and b) Test Be with the corrected conditioning temperature T
B'
and a second temperature adjustment . 24
Figure B.4 – a) Test Bd and b) Test Be with a preliminary temperature below the
corrected conditioning temperature T and a second temperature adjustment . 25
B'
Figure B.5 – Nomogram with example of application of the procedure. 26

Table 1 – Preferred values for the high conditioning temperature T . 11
B
Table 2 – Preferred values for the exposure time t . 11
Table A.1 – Relationship of suffixes between Test A: Cold, and Test B: Dry heat . 19

IEC 60068-2-2:2025 © IEC 2025
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Environmental testing -
Part 2-2: Tests - Test B: Dry heat

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) 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 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 https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 60068-2-2 has been prepared by IEC technical committee 104: Environmental conditions,
classification and methods of test. It is an International Standard.
This sixth edition cancels and replaces the fifth edition published in 2007. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) revision of the introduction and scope;
b) inclusion of new figures and symbols for clarification purposes;
c) clarification of the test procedure for ascertaining high or low air velocity in the test chamber;
d) clarification of the requirements for measuring points around, on or in specimens;
e) reintroduction of the nomogram procedure for the correction of the conditioning temperature
when testing with high air velocity (Test Bd and Test Be);
IEC 60068-2-2:2025 © IEC 2025
f) revision of the temperature tolerances of the test;
g) revision of standardized requirements for the relevant specification and test report;
h) inclusion of the advantages and disadvantages of the testing procedures.
The text of this International Standard is based on the following documents:
Draft Report on voting
104/1108/FDIS 104/1128/RVD
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 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.
A list of all the parts of the IEC 60068 series, under the general title Environmental 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, or
– revised.
IEC 60068-2-2:2025 © IEC 2025
INTRODUCTION
The working ranges and performance of equipment and machinery can be significantly affected
or limited by ambient temperatures. The degree of this influence can depend on temperature
distributions of the environment as well as temperatures on components of the device itself. In
order to determine the existing degree of influence and to ensure that the device is suitably
designed for its ambient conditions, tests are carried out with cold (IEC 60068-2-1) or dry heat,
or both. During the test detailed in this document, it will be taken into account whether the
tested device itself emits heat or not.
Reducing the air flow within the test chamber can be required to reduce the air velocity at heat-
dissipating specimens. This can be achieved by using air baffles or adjusting the air flow of the
test chamber. If the reduction of air velocity is not practical or possible due to the required test
conditions, this document provides an alternative test procedure without the need for adjustable
air flow as well as guidance on selecting the applicable test procedure.

IEC 60068-2-2:2025 © IEC 2025
1 Scope
This part of IEC 60068 specifies dry heat temperature tests that are applicable to non-heat-
dissipating and heat-dissipating specimens, to determine the ability of components, equipment
or other articles to be used, transported or stored at high temperature.
This document is applicable to energized as well as non-energized specimens that normally
achieve temperature stability during the test. The specimens can be subject to test in packed
condition (to simulate transportation and storage) or in unpacked condition (to simulate use).
This document does not specify tests to determine the impact of temperature changes on
specimens.
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 60068-1, Environmental testing - Part 1: General and guidance
IEC 60068-5-2, Environmental testing - Part 5-2: Guide to drafting of test methods - Terms and
definitions
IEC 60721 (all parts), Classification of environmental conditions
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60068-1,
IEC 60068-5-2 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
– IEC Electropedia: available at https://www.electropedia.org/
– ISO Online browsing platform: available at https://www.iso.org/obp
3.1
low air velocity
velocity of conditioning airflow within a working space which is sufficient to maintain conditions
but low enough so that the temperature at the relevant point or relevant points on the test
specimen is not reduced by more than 5 K by the influence of the circulation of the air
Note 1 to entry: The relevant points to be considered are determined by the relevant test specification.
3.2
high air velocity
velocity of conditioning airflow within a working space, which, in order to maintain conditions,
also reduces the temperature at the relevant point or relevant points on the test specimen by
more than 5 K by the influence of the circulation of the air
IEC 60068-2-2:2025 © IEC 2025
4 Symbols
T high conditioning temperature [°C]
B
corrected high conditioning temperature (nomogram procedure) [°C]
T
B'
T temperature of standard atmospheric conditions for measurement and tests (15 °C to
STD
35 °C) [°C]
T measured ambient temperature in the vicinity of the specimen, either in the test
Ca
chamber or the laboratory air, without forced convection (see 5.2) [°C]
T measured test chamber temperature with forced convection (see 5.2) [°C]
Cb
T temperature of the energized specimen at the specified conditioning temperature [°C]
S
T temperature of the energized specimen at the temperature of standard atmospheric
Sa
conditions without forced convection (see 5.2) [°C]
T temperature of the energized specimen at the temperature of standard atmospheric
Sb
conditions with forced convection (see 5.2) [°C]
∆T temperature difference between the energized specimen and the air [K]
S
∆T temperature difference between the energized specimen without forced convection
Sa/b
(T ) and with forced convection (T ) at the temperature of standard atmospheric
Sa Sb
conditions [K]
dT temperature change rate [K/min]
R
t stabilization time of specimen temperature before exposure to the high conditioning
s
temperature [min or h]
t stabilization time of specimen temperature after energizing [min or h]
s0
t exposure time of the specimen to the high conditioning temperature [h]
5 Application of tests for non-heat-dissipating specimens versus tests for
heat-dissipating specimens
5.1 General
This test is subdivided as follows:
– Test Bb: Dry heat for non-heat-dissipating specimens;
– Test Bd: Dry heat for heat-dissipating specimens that are energized after initial temperature
stabilization;
– Test Be: Dry heat for heat-dissipating specimens that are energized throughout the test.
A specimen, while energized, is considered to be heat-dissipating only if the hottest point on its
surface or any other relevant point, measured in free air conditions (i.e. low air velocity
circulation), is more than 5 K above the ambient temperature of the surrounding atmosphere
after temperature stability has been reached (see IEC 60068-1).
NOTE 1 In some cases, for example for test specimens with air-permeable housings, the relevant measuring points
can be located inside the external housing.
Tests of heat-dissipating and non-heat-dissipating specimens generally differ in the air velocity
applied. Non-heat-dissipating specimens are typically tested at high air velocity to reduce the
time required to reach temperature stability. Heat-dissipating specimens are generally tested
at low air velocity to allow for the formation of local hotspots similar to those that would appear
in installed applications. Annex A gives an overview of the relevant test conditions and shows
the relationship of suffixes between Test A: Cold and Test B: Dry heat.
IEC 60068-2-2:2025 © IEC 2025
It is possible that testing with low air velocity does not apply to heat-dissipating specimens with
an external housing and built-in fan, provided that the representative measuring point is located
at a point inside the external housing which is not affected by external air movement. Ensure
that the induced air movement does not interfere with the operation of the built-in fan, if not
specified otherwise.
NOTE 2 The induced air movement can have an influence on the operation of a built-in fan if both air movements
act either in the same or opposite direction.
Where it is not feasible to test heat-dissipating specimens with low air velocity, for example due
to the required test conditions, Annex B gives an alternative procedure for testing with high air
velocity.
The relevant specification shall state which test procedure shall be applied. The advantages
and disadvantages of both test procedures should be considered when specifying the intended
test. For more information on these advantages and disadvantages, see Annex C.
When the relevant specification calls for a storage or transportation test or does not specify an
applied load during the test, Test Bb applies.
5.2 Ascertaining high or low air velocity in the test chamber
To ascertain, whether high or low air velocity prevails in the test chamber, the cooling effect of
the air movement on the specimen shall be determined. Therefore, the specimen's temperature
shall be measured with and without forced convection by the test chamber's fan. Both
temperatures shall be compared in accordance with the following procedure. It is recommended
to ascertain the prevailing air velocity in the test chamber for every specimen, since the
occurring cooling effect can vary for different specimens.
Under standard atmospheric conditions for measurements and tests (see IEC 60068-1) with an
air velocity < 0,2 m/s, achieved without forced convection, the heat-dissipating specimen shall
be switched on or electrically loaded as specified for the high temperature at which the test is
to be carried out.
When temperature stability of the specimen has been reached, the temperature of a
representative point around or on the specimen and the ambient temperature T shall be
Ca
measured using a suitable monitoring device. Either the hottest point or any point of particular
interest on the specimen can be used as representative point for measuring the temperature of
the energized specimen T without forced convection.
Sa
NOTE 1 To determine the representative point, an infrared camera can be helpful.
The temperature reached at each point shall then be noted. This measurement may be done in
an open test chamber (e.g. with an opened door or a lifted test space enclosure, if applicable)
or outside of the test chamber to prevent an improper temperature rise of the surrounding air.
NOTE 2 The operation of a heat-dissipating specimen in a closed and switched-off test chamber leads to a
temperature rise within the test space. In a small test chamber or with a large heat load, the temperature rise can
influence the measurement result.
NOTE 3 The temperature T is the temperature in the vicinity of the specimen during the measurement without
Ca
forced convection. It can be the temperature in the test chamber or the temperature of the laboratory air, depending
on where the test was done.
The specimen is then introduced into the test chamber, if applicable, and test chamber is
switched on. The temperature is set to the previously recorded temperature T .
Ca
IEC 60068-2-2:2025 © IEC 2025
Once temperature stability of the energized specimen has been achieved, the temperature of
the representative point and the test chamber temperature T shall be measured. The
Cb
temperatures T and T shall be measured at the same point around or on the specimen.
Sa Sb
NOTE 4 The temperature T is the test chamber temperature during the test with forced convection. It can vary
Cb
marginally from temperature T .
Ca
The following applies:
∆T =TT–
(1)
Sa/b Sa Sb
If the temperature difference ∆T between the temperature of the specimen with and without
Sa/b
forced convection is more than 5 K (or a value stated by the relevant specification) this value
shall be noted in the test report and the test chamber is considered to have high air velocity.
The specimen is then switched off and any operational loading conditions removed.
For some specimens, for example large specimens or specimens with a complex geometry,
more than one representative point around or on the specimen can be used for measuring the
temperature of the specimen. For some specimens, for example specimens with air-permeable
housings, the relevant measuring point or points can be located inside the external housing.
The relevant specification shall state the number and location of the measuring points.
Figure 1 shows a comparison of examples of temperature profiles in test chambers with high
and low air velocity.
a) temperature profile of an energized heat- b) temperature profile of an energized heat-
dissipating specimen in a test chamber with high dissipating specimen in a test chamber with low air
air velocity velocity
Figure 1 – Examples of temperature profiles of energized heat-dissipating specimens in
test chambers with a) high air velocity and b) low air velocity
5.3 Temperature monitoring
The air temperature in the test chamber shall be measured by temperature sensors located at
such a distance from the specimen that the effect of the dissipation is negligible. Suitable
precautions shall be taken to avoid heat radiation affecting these measurements.
IEC 60068-2-2:2025 © IEC 2025
5.4 Packaging
Packaging shall be removed unless the relevant specification requires it to remain in place or
heating elements are incorporated in the package. For storage and transportation tests, the
specimen may be tested with its packaging in place.
NOTE Packaged specimens are expected to stabilize at chamber temperature after a certain exposure time.
5.5 Background
To facilitate the choice of test method, a diagrammatic representation of the various procedures
is given in Figure 2.
Figure 2 – Block diagram of the test procedures and
applicable selection criteria of Test B: Dry heat
6 Test descriptions
6.1 General
For each test, the test chamber shall be at the temperature of standard atmospheric condition
T , 15 °C to 35 °C, when the test specimens are introduced. The temperature shall then be
STD
gradually raised to the high conditioning temperature T appropriate to the degree of severity,
B
as specified in the relevant specification.
NOTE 1 The gradual temperature change prevents detrimental effects on the specimen caused by thermal stress
due to the change of temperature. For more information on thermal stress caused by temperature change, see
IEC 60068-2-14.
The temperature change rate dT within the chamber shall not exceed 1 K/min, averaged over
R
a period of not more than 5 min. The relevant specification shall define the functioning of the
specimen under test. Further requirements for each test are noted in 6.3, 6.4 and 6.5.
Any cooling or heating devices of the specimen shall be in accordance with the requirement in
the relevant specification.
NOTE 2 IEC 60068-3-1 provides general guidance for the performance of Tests A and B. IEC 60068-3-6 provides
guidance for the confirmation of performance of test chambers without specimen. IEC 60068-3-7 provides further
information on testing with test specimens within the test chamber.
IEC 60068-2-2:2025 © IEC 2025
6.2 Severities
6.2.1 General
The severities, as indicated by the high conditioning temperature T and the exposure time t ,
B 1
shall be specified by the relevant specification. If these values are not given in the relevant
specification, they shall be:
a) chosen from the values given in Table 1 (see 6.2.2) and Table 2 (see 6.2.3); or
b) derived from known environments, if these give significantly different values; or
c) derived from other known sources of relevant data (for example the IEC 60721 series or
field data from the specimen).
6.2.2 High conditioning temperature T
B
Table 1 – Preferred values for the high conditioning temperature T
B
+1 000 °C +800 °C +630 °C +500 °C +400 °C
+315 °C +250 °C +200 °C +175 °C +155 °C
+125 °C +100 °C +85 °C +70 °C +65 °C
+60 °C +55 °C +50 °C +45 °C +40 °C
+35 °C +30 °C
6.2.3 Exposure time t
Table 2 – Preferred values for the exposure time t
2 h 16 h 72 h 96 h
168 h 240 h 336 h 1 000 h
NOTE For further information on the test duration, IEC TR 60721-4 series can be helpful.
6.3 Test Bb: Dry heat for non-heat-dissipating specimens
Test Bb is intended for non-heat-dissipating specimens which are subjected to the high
conditioning temperature T with high air velocity for a time long enough for the specimen to
B
achieve temperature stability and maintain the test conditions for the specified exposure time
t .
The specimen is introduced into the test chamber, which is at the temperature of standard
atmospheric condition for measurement and tests T , 15 °C to 35 °C. The temperature is then
STD
adjusted to the high conditioning temperature T appropriate to the degree of severity as
B
specified in the relevant specification. After temperature stability of the test specimen has been
reached, the specimen stays exposed to the high conditioning temperature T for the specified
B
exposure time t (see Figure 3). A representative point (or points) on or inside the specimen
may be used for this measurement.
NOTE 1 For further information on thermal stability, see IEC 60068-1.
If a measuring point on or inside the specimen can damage the specimen, a representative
point (or points) around the specimen may be used instead.
IEC 60068-2-2:2025 © IEC 2025
Figure 3 – Test Bb: Dry heat for non-heat-dissipating and non-operating specimens
Specimens under test are normally in non-operating conditions. High air velocity circulation is
normally used for this test.
NOTE 2 In the case of a non-heat-dissipating specimen in Test Bb, high air velocity in the test chamber can be
assumed, when no measures are taken to disturb the air flow (e.g. by bulkheading installations, like perforated plates
or air baffles, or the reduction of the overall air flow within the test chamber).
Specimens that are required to be operational but do not meet the requirements of being heat
dissipating shall be energized after temperature stabilization at the high conditioning
temperature T is achieved (see Figure 4), if not specified otherwise. A functional test shall be
B
performed as specified in the relevant specification, if applicable. A further stabilization time of
the specimen temperature (t ) can be necessary. The specimen shall then be exposed to the
s0
high conditioning temperature T for the specified exposure time t .
B 1
Figure 4 – Test Bb: Dry heat for non-heat-dissipating, operating specimens
IEC 60068-2-2:2025 © IEC 2025
6.4 Test Bd: Dry heat for heat-dissipating specimens that are energized after initial
temperature stabilization
Test Bd is intended for heat-dissipating specimens which are subjected to the high conditioning
temperature T with low air velocity for a time long enough for the specimens to achieve
B
temperature stability and maintain the test conditions for the specified exposure time t . The
specimens are energized after the initial temperature stabilization.
The specimen is introduced into the test chamber, which is at the temperature of standard
atmospheric condition for measurement and tests T , 15 °C to 35 °C. The temperature is then
STD
adjusted to the high conditioning temperature T appropriate to the degree of severity as
B
specified in the relevant specification.

Figure 5 – Test Bd: Dry heat for heat-dissipating specimens
that are energized after initial temperature stabilization
After the temperature stabilization period of the specimen t before exposure to the high
s
conditioning temperature, the specimen is energized, stabilized again and then exposed to the
high conditioning temperature T for the specified exposure time t . A representative point (or
B 1
points) on or inside the specimen may be used for this measurement. The specimen shall
remain in the operating condition as specified by the relevant specification.
NOTE 1 For further information on thermal stability, see IEC 60068-1.
If a measuring point on or inside the specimen can damage the specimen, a representative
point (or points) around the specimen may be used instead.
Low air velocity circulation is normally used for this test. If necessary, a test is performed to
determine if the test chamber fulfils the requirements of low air velocity (see 5.2). If low air
velocity is not suitable for this test, the test procedure described in Annex B may be used.
NOTE 2 For further information on testing with low air velocity, see Annex C.
IEC 60068-2-2:2025 © IEC 2025
6.5 Test Be: Dry heat for heat-dissipating specimens that are energized throughout
the test
Test Be is intended for heat-dissipating specimens which are subjected to the high conditioning
temperature T with low air velocity for a time long enough for the specimen to achieve
B
temperature stability and maintain the test conditions for the specified exposure time t . The
specimens are energized during the temperature change of the test chamber temperature and
the specified exposure time t .
The specimen is introduced into the test chamber, which is at the temperature of standard
atmospheric condition for measurement and tests T , 15 °C to 35 °C. The specimen shall
STD
then be switched on or electrically loaded and checked to ascertain whether it is capable of
functioning in accordance with the relevant specification.
The specimen shall remain in the operating condition as specified by the relevant specification.
Following the temperature stabilization period of the specimen after energizing t the test
s0
chamber temperature is adjusted to the high conditioning temperature T appropriate to the
B
degree of severity as specified in the relevant specification.

Figure 6 – Test Be: Dry heat for heat-dissipating specimens that are required to be
energized throughout the test
After the stabilization period of the specimen t before exposure to the high conditioning
s
temperature, the specimen is exposed to the high conditioning temperature T for the specified
B
exposure time t . A representative point (or points) on or inside the specimen may be used for
this measurement.
NOTE 1 For further information on thermal stability, see IEC 60068-1.
If a measuring point on or inside the specimen can damage the specimen, a representative
point (or points) around the specimen may be used instead.
Low air velocity circulation is normally used for this test. If necessary, a test is performed to
determine if the test chamber fulfils the requirements of low air velocity (see 5.2). If low air
velocity is not suitable for this test, the test procedure described in Annex B may be used.
NOTE 2 For further information on testing with low air velocity, see Annex C.
IEC 60068-2-2:2025 © IEC 2025
7 Testing procedure
7.1 General
The test chamber shall be large enough compared with the size and amount of heat-dissipation
of the test sample.
The temperature shall be within ± 2 K of the test severity temperature during the steady-state
condition. The air temperature in the working space shall be measured in accordance with 5.3.
NOTE 1 For further information on the working space, IEC 60068-3-6 can be helpful.
Where due to the size of the chamber it is not feasible to maintain these tolerances, the
tolerance may be widened to ±3 K up to 100 °C, ±5 K from 100 °C to 200 °C and ±10 K from
200 °C to 315 °C. When this is done, the tolerance used should be noted in the test report.
When the high conditioning temperature T is above 315 °C, the tolerance achieved at the
B
temperature should be specified in relevant specification.
The temperature tolerance given in this document is intended to take into account errors in the
measurement, slow changes of temperature, and temperature variations of the working space.
The temperature refers to the control sensor of the test chamber, if not specified otherwise.
The tolerances stated in this document do not take measurement uncertainty into consideration.
NOTE 2 This tolerance is valid for an empty
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