IEC 60068-2-2:2007

Environmental testing - Part 2-2: Tests - Test B: Dry heat

IEC 60068-2-2:2007 Deals with dry heat tests applicable both to heat-dissipating and non heat-dissipating specimens. For non heat-dissipating specimens, Tests Bb and Bd do not deviate essentially from earlier issues. The object of the dry heat test is limited to the determination of the ability of components, equipment or other articles to be used, transported or stored at high temperature. These dry heat tests do not enable the ability of specimens to withstand or operate during the temperature variations to be assessed. In this case, it would be necessary to use IEC 60068-2-14 Test N: Change of temperature. The dry heat tests are subdivided as follows:
- Dry heat test for non heat-dissipating specimens with gradual change of temperature, Bb.
- Dry heat tests for heat-dissipating specimens with gradual change of temperature, Bd;
with gradual change of temperature, specimen powered throughout, Be. The procedures given in this standard are normally intended for specimens that achieve temperature stability during the performance of the test procedure. The main changes from the previous edition are as follows: Tests Ba and Bc have been deleted since they were more severe tests than Test Nb, IEC 60068-2-14: Change of temperature. Secondly it was considered justified to delete the 3 % value on the temperature difference between the chamber air and the wall temperatures. Thirdly it is proposed that the test specimen be powered throughout the test where required; and, finally, the annexes have been removed.

Essais d'environnement - Partie 2-2: Essais - Essai B: Chaleur sèche

IEC 60068-2-2:2007 Traite des essais de chaleur sèche applicables à la fois aux spécimens dissipant de l'énergie et à ceux ne dissipant pas d'énergie. Les essais Bb et Bd destinés à des spécimens ne dissipant pas d'énergie ne présentent pas de modifications importantes par rapport aux éditions précédentes. Le but de l'essai de chaleur sèche se limite à la détermination de l'aptitude des composants, équipements ou autres articles à être utilisés, transportés ou stockés à haute température. Ces essais de chaleur sèche ne permettent pas de vérifier l'aptitude des spécimens à subir ou à fonctionner pendant les variations de température. Dans ce cas, il serait nécessaire d'utiliser l'essai N de la CEI 60068-2-14: Variations de température. Les essais de chaleur sèche se subdivisent de la façon suivante:
- Essai de chaleur sèche pour spécimens ne dissipant pas d'énergie avec variation lente de la température, Bb.
- Essais de chaleur sèche pour spécimens dissipant de l'énergie avec variation lente de la température, Bd;
avec variation lente de la température, pour les spécimens dissipant partout, Be. La procédure décrite dans cette norme est normalement prévue pour les spécimens qui atteignent la stabilité thermique pendant le déroulement de l'essai. Les principaux changements par rapport à l'édition précédente sont les suivants: Les essais Ba et Bc ont été retirés puisqu'ils étaient plus sévères que l'essai Nb de la CEI 60068-2-14: Variations de température. Deuxièmement, il a été considéré justifié de supprimer la valeur de 3 % sur la différence de température entre l'air de la chambre d'essai et les températures des parois. Troisièmement, il est proposé et non plus exigé que le spécimen d'essai soit mis en fonctionnement durant l'essai; et, pour finir, les annexes ont été retirées.

General Information

• Status: Published
• Publication Date: 15-Jul-2007
• ICS: 19.040 - Environmental testing
• Technical Committee: TC 104 - Environmental conditions, classification and methods of test
• Drafting Committee: MT 16 - TC 104/MT 16
• Current Stage: PPUB - Publication issued
• Start Date: 16-Jul-2007
• Completion Date: 15-Sep-2007

Relations

• Revised: IEC 60068-2-2:2025 - Environmental testing - Part 2-2: Tests - Test B: Dry heat
• Effective Date: 05-Sep-2023

Overview

IEC 60068-2-2:2007 is an international standard developed by the International Electrotechnical Commission (IEC) that defines environmental testing methods specifically for dry heat exposure. It is part of the broader IEC 60068 series concerning environmental testing of electrical, electronic, and related equipment.

This standard outlines test procedures focused on determining the ability of components, equipment, or articles to withstand high temperature conditions during storage, transportation, or usage. Importantly, it targets tests with gradually applied dry heat to both heat-dissipating and non heat-dissipating specimens, ensuring their reliability and durability in elevated temperature environments.

IEC 60068-2-2:2007 excludes assessment of temperature variation tolerance; such assessments fall under IEC 60068-2-14 (Test N: Change of Temperature). The dry heat test emphasizes evaluation under stable, controlled thermal conditions, reflecting real-world operational or storage scenarios where high temperature endurance is critical.

Key Topics

• Test Categories:

  • Test Bb: Dry heat for non heat-dissipating specimens with gradual temperature change
  • Test Bd: Dry heat for heat-dissipating specimens with gradual temperature change (specimens unpowered during conditioning)
  • Test Be: Dry heat for heat-dissipating specimens with gradual temperature change, powered throughout the test

• Scope and Objectives:

  • Assess endurance of specimens against long-term exposure to dry heat
  • Evaluate suitability for transport, storage, and operation at high temperatures
  • Exclude rapid temperature cycling or shock evaluation

• Test Conditions and Parameters:

  • Gradual temperature increase to avoid thermal shock
  • Air velocity control inside test chambers (low or high velocity depending on specimen type)
  • Specimen temperature monitoring to confirm stability and uniform heat application
  • Power supply requirements for heat-dissipating specimens during testing

• Changes from Previous Editions:

  • Removal of Tests Ba and Bc due to severity overlap with Test Nb (IEC 60068-2-14)
  • Elimination of 3% limit on temperature differences between chamber air and wall temperature
  • Increased focus on powering specimens continuously during test where applicable
  • Removal of annexes to streamline test procedures

Applications

IEC 60068-2-2:2007 is widely used in industries requiring assurance that devices and components can endure elevated temperatures without degradation. Common applications include:

• Electrical and Electronic Equipment Testing
  Manufacturers use this standard to qualify products such as circuits, sensors, transformers, and other electronic assemblies that may experience harsh thermal environments.

• Component Reliability Verification
  Ensuring that non heat-dissipating items like resistors, capacitors, and connectors maintain integrity and function when exposed to heat during shipping or in service.

• Heat-Dissipating Device Endurance
  Testing powered equipment such as power supplies and heat-generating devices to verify performance under prolonged heat exposure, critical for consumer electronics, automotive systems, and industrial control units.

• Transport and Storage Validation
  Assessing packaging and product robustness when subjected to elevated temperatures in transit or storage, enhancing product lifecycle and reducing failure rates.

• Quality Control and Certification
  Providing a standardized basis for compliance with international market requirements and safety certifications related to thermal endurance.

Related Standards

IEC 60068-2-2:2007 is part of a comprehensive suite of environmental testing standards addressing different conditions and stressors:

• IEC 60068-2-14: Change of Temperature (Test N)
  Complementary to dry heat testing, this evaluates specimen ability to handle rapid temperature fluctuations and thermal cycling.

• IEC 60068-1: General and Guidance
  Provides overarching principles and terminology used across environmental test methods.

• IEC 60068-3-1 and IEC 60068-3-5: Supporting Documentation and Guidance
  Offers background information and confirmation procedures for temperature test chambers, ensuring reliable test environments.

• IEC 60068-5-2: Guide to Drafting of Test Methods
  Key for understanding test definitions, conditions, and terminology that impact applicability and interpretation of results.

• IEC 60721 Series: Classification of Environmental Conditions
  Provides classifications and descriptions of environmental conditions relevant for selecting appropriate test methods.

---

Keywords: IEC 60068-2-2, dry heat test, environmental testing, heat-dissipating specimens, non heat-dissipating specimens, temperature stability, electrical equipment testing, electronic components, thermal endurance, international standard, IEC environmental tests.

Standards Content (Sample)

IEC 60068-2-2
Edition 5.0 2007-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
BASIC SAFETY PUBLICATION
PUBLICATION FONDAMENTALE DE SÉCURITÉ
Environmental testing –
Part 2-2: Tests – Test B: Dry heat

Essais d’environnement –
Partie 2-2: Essais – Essai B: Chaleur sèche

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IEC 60068-2-2
Edition 5.0 2007-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
BASIC SAFETY PUBLICATION
PUBLICATION FONDAMENTALE DE SÉCURITÉ
Environmental testing –
Part 2-2: Tests – Test B: Dry heat

Essais d’environnement –
Partie 2-2: Essais – Essai B: Chaleur sèche

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
N
CODE PRIX
ICS 19.040 ISBN 2-8318-9229-5
– 2 – 60068-2-2 © IEC:2007
CONTENTS
FOREWORD.4
INTRODUCTION.6

1 Scope.7
2 Normative references .7
3 Terms and definitions .8
4 Application of tests for non heat-dissipating specimens versus tests for heat-
dissipating specimens .8
4.1 General .8
4.2 Ascertaining high or low air velocity in the test chamber.8
4.3 Application of tests with sudden change of temperature versus tests with
gradual change of temperature.9
4.4 Testing of heat-dissipating specimens .9
4.5 Temperature monitoring .9
4.6 Packaging .9
4.7 Diagrammatic representations .9
5 Test descriptions .10
5.1 General .10
5.2 Test Bb: Dry heat for non heat-dissipating specimens with gradual change of
temperature.10
5.2.1 Object .10
5.2.2 General description .11
5.3 Test Bd: Dry heat for heat-dissipating specimens with gradual change of
temperature that are not powered during the conditioning period.11
5.3.1 Object .11
5.3.2 General description .11
5.3.3 Energising the specimen .11
5.4 Test Be: Dry heat for heat-dissipating specimens with gradual change of
temperature that are required to be powered throughout the test.11
5.4.1 Object .11
5.4.2 General description .12
6 Test procedure .12
6.1 Confirmation of performance .12
6.2 Working space .12
6.3 Thermal radiation .12
6.4 Mounting .13
6.5 Severities .13
6.5.1 General .13
6.5.2 Temperature.13
6.5.3 Duration .13
6.6 Preconditioning .13
6.7 Initial measurements .13
6.8 Conditioning .13
6.8.1 Steady state conditions .13
6.8.2 Absolute humidity .14
6.9 Intermediate measurements .14
6.10 Final temperature ramp .14

60068-2-2 © IEC:2007 – 3 –
6.11 Recovery.14
6.12 Specimen with artificial cooling.14
6.13 Final measurements .14
7 Information to be given in the relevant specification .15
8 Information to be given in the test report .15

Figure 1 – Block diagram Tests B: Dry Heat.10

– 4 – 60068-2-2 © IEC:2007
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
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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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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
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5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
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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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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 60068-2-2 has been prepared by IEC technical committee 104:
Environmental conditions, classification and methods of test.
This fifth edition of IEC 60068-2-2 cancels and replaces the fourth edition issued in 1974. It
includes the revised text of the fourth edition, amendment 1 issued in 1993 and amendment 2
issued in 1994.
It has the status of a basic safety publication in accordance with IEC Guide 104.
The main changes from the previous edition are as follows: Tests Ba and Bc have been
deleted since they were more severe tests than Test Nb, IEC 60068-2-14: Change of
temperature. Secondly it was considered justified to delete the 3 % value on the temperature
difference between the chamber air and the wall temperatures. Thirdly it is proposed that the
test specimen be powered throughout the test where required; and, finally, the annexes have
been removed.
60068-2-2 © IEC:2007 – 5 –
The text of this standard is based on the following documents:
FDIS Report on voting
104/412/FDIS 104/430/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.
This standard has been drafted in accordance with the ISO/IEC Directives, Part 2.
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 publication will remain unchanged until
the maintenance result 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 – 60068-2-2 © IEC:2007
INTRODUCTION
RELATIONSHIP OF SUFFIXES BETWEEN TESTS A: COLD,
AND TESTS B: DRY HEAT
The relationship of suffixes between Tests A: Cold, and Tests B: Dry heat, is shown in the
following table:
Tests A: Cold Tests B: Dry heat
Suffix Specimen Temperature Air velocity Specimen Temperature Air velocity
letter type change type change
a Withdrawn Withdrawn
b Non heat Gradual High preferred Non heat Gradual High preferred
c Withdrawn Withdrawn
d Heat Gradual Low preferred Heat Gradual Low preferred
dissipating
e Heat Gradual Low preferred Heat, Gradual Low preferred
dissipating powered
powered throughout
throughout
60068-2-2 © IEC:2007 – 7 –
ENVIRONMENTAL TESTING –
Part 2-2: Tests – Test B: Dry heat

1 Scope
This standard deals with dry heat tests applicable both to heat-dissipating and non heat-
dissipating specimens. For non heat-dissipating specimens, Tests Bb and Bd do not deviate
essentially from earlier issues.
The object of the dry heat test is limited to the determination of the ability of components,
equipment or other articles to be used, transported or stored at high temperature.
These dry heat tests do not enable the ability of specimens to withstand or operate during the
temperature variations to be assessed. In this case, it would be necessary to use IEC 60068-
2-14 Test N: Change of temperature.
The dry heat tests are subdivided as follows:
Dry heat test for non heat-dissipating specimens
– with gradual change of temperature, Bb.
Dry heat tests for heat-dissipating specimens
– with gradual change of temperature, Bd;
– with gradual change of temperature, specimen powered throughout, Be.
The procedures given in this standard are normally intended for specimens that achieve
temperature stability during the performance of the test procedure.
2 Normative references
IEC 60068-1:1988, Environmental testing – Part 1: General and guidance
IEC 60068-3-1, Environmental testing – Part 3: Background information – Section one: Cold
and dry heat tests
IEC 60068-3-5, Environmental testing – Part 3-5: Supporting documentation and guidance –
Confirmation of the performance of temperature chambers
IEC 60068-3-7, Environmental testing – Part 3-7: Supporting documentation and guidance –
Measurements in temperature chambers for tests A and B (with load)
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

– 8 – 60068-2-2 © IEC:2007
3 Terms and definitions
For the purposes of this document, the definitions in IEC 60068-5-2 and the following
definitions apply.
3.1
low air velocity in the working space
the velocity of conditioning airflow within a working space which is sufficient to maintain
conditions but low enough so that the temperature at any point on the test specimen is not
reduced by more than 5 K by the influence of the circulation of the air (if possible, not more
than 0,5 m/s)
3.2
high air velocity in the working space
the velocity of conditioning airflow within a working space, which, in order to maintain
conditions, also reduces the temperature at any point on the test specimen by more than 5 K
by the influence of the circulation of the air
4 Application of tests for non heat-dissipating specimens versus tests for
heat-dissipating specimens
4.1 General
The temperature chamber(s) shall be constructed and verified in accordance with
specifications IEC 60068-3-5 and IEC 60068-3-7.
Further guidance for the dry heat and cold tests can be found in IEC 60068-3-1, and general
guidance in IEC 60068-1.
A specimen is considered heat-dissipating only if the hottest point on its surface, 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
4.8 of IEC 60068-1). When the relevant specification calls for a storage or transportation test
or does not specify an applied load during the test, the Dry Heat Test Bb will apply.
4.2 Ascertaining high or low air velocity in the test chamber
Under standard atmospheric conditions for measurements and test (see IEC 60068-1) with an
air velocity <0,2 m/s, the 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 number
of representative points around or on the specimen shall be measured using a suitable
monitoring device. The temperature rise that occurs at each point shall then be noted.
The chamber air flow is switched on and, once temperature stability has been achieved, the
temperature of the representative points shall again be measured. If the temperatures differ
from those measured without air flow by 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 velocity circulation. The specimen is then switched off and any loading conditions
removed.
60068-2-2 © IEC:2007 – 9 –
4.3 Application of tests with sudden change of temperature versus tests with gradual
change of temperature
In Tests Bb, Bd and Be with gradual change of temperature, the specimen is introduced into
the test chamber, the latter being at the laboratory temperature. The temperature in the
chamber is then increased gradually so as to cause no detrimental effects on the test
specimen due to the temperature change.
4.4 Testing of heat-dissipating specimens
Tests Bd and Be describe procedures for testing heat-dissipating specimens with low air
velocity circulation. This is to allow localised hot spots to develop within the specimen similar
to those that would appear in installed applications.
4.5 Temperature monitoring
The air temperature in the 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 should be taken to avoid heat radiation affecting these measurements. For more
information see IEC 60068-3-5.
4.6 Packaging
For storage and transportation tests, equipment may be tested with its packaging in place.
However, as these tests are steady state tests the equipment will eventually stabilise at
chamber’s temperature. Packaging shall be removed unless the relevant specification
requires it to remain in place or heating elements are incorporated in the package.
4.7 Diagrammatic representations
To facilitate the choice of test method, a diagrammatic representation of the various
procedures is given in Figure 1.

– 10 – 60068-2-2 © IEC:2007
TesTestts B:s B:
DrDryy He Heatat
NoNo
HHeat eat
DDiississippaattiing?ng?
YesYes
PowPoweered red
NoNo
duduringring
conditioconditionniningg
peperiodriod??
YesYes
Test BTest Bbb TestTest B Bdd TeTest Best Be
See CSee Cllaauusese See CSee Cllauausese See CSee Cllauausese
5.25.2 5.35.3 5.5.44
IEC  1181/07
Figure 1 – Block diagram Tests B: Dry Heat
5 Test descriptions
5.1 General
Tests Bb, Bd, and Be are similar. Differences are noted in Subclauses 5.2.2, 5.3.2 and 5.4.2.
All other portions of the tests are the same, starting with Clause 6. The rate of change of
temperature within the chamber shall not exceed 1 K per minute, averaged over a period of
not more than 5 min. The relevant specification shall define the functioning of the specimen
under test.
Care shall be taken that any cooling devices of the specimen are in accordance with the
prescription in the relevant specification.
5.2 Test Bb: Dry heat for non heat-dissipating specimens with gradual change of
temperature
5.2.1 Object
This procedure is for non heat-dissipating specimens which are subjected to an elevated
temperature for a time long enough for the specimen to achieve temperature stability.

60068-2-2 © IEC:2007 – 11 –
5.2.2 General description
The specimen is introduced into the chamber, which is at the temperature of the laboratory.
The temperature is then adjusted to the temperature appropriate to the degree of severity as
specified in the relevant specification. After temperature stability of the test specimen has
been reached, the specimen is exposed to these conditions for the specified duration. For
specimens that are required to be operational (even though they do not meet the
requirements of being heat dissipating) power shall then be applied to the specimen and a
functional test is performed as necessary. A further period of stabilization may be necessary
and the specimen shall then be exposed to the high temperature conditions for a duration as
specified in the relevant specification.
Specimens under test are normally in non-operating conditions.
High air velocity circulation is normally used for this test.
5.3 Test Bd: Dry heat for heat-dissipating specimens with gradual change of
temperature that are not powered during the conditioning period
5.3.1 Object
This procedure is for heat dissipating specimens which are subjected to an elevated
temperature for a time long enough for the specimen to achieve temperature stability.
5.3.2 General description
If necessary, a test is performed to determine if the test facility fulfils the requirements of a
low air velocity chamber or not. The specimen is introduced into the chamber, which is at the
temperature of the laboratory. The temperature is then adjusted to the temperature
appropriate to the degree of severity as specified in the relevant specification.
Low air velocity circulation is normally used for this test.
5.3.3 Energising the specimen
The specimen shall 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 in accordance with the duty cycle and at
the loading condition (if applicable) as prescribed by the relevant specification.
After temperature stability of the test specimen has been reached, the specimen is exposed to
these conditions for the duration as specified in the relevant specification. Low air velocity
circulation is normally used for this test.
5.4 Test Be: Dry heat for heat-dissipating specimens with gradual change of
temperature that are required to be powered throughout the test
5.4.1 Object
This procedure is for heat dissipating specimens which are subjected to an elevated
temperature for a time long enough for the specimen to achieve temperature stability and
which are required to be powered throughout the test period.

– 12 – 60068-2-2 © IEC:2007
5.4.2 General description
If necessary, a test is performed to determine if the test facility fulfils the requirements of a
low air velocity chamber or not. The specimen is introduced into the chamber, which is at the
temperature of the laboratory. The specimen shall 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 in accordance with the duty cycle and at
the loading condition (if applicable) as prescribed by the relevant specification.
The temperature is then adjusted to the temperature appropriate to the degree of severity as
specified in the relevant specification.
After temperature stability of the test specimen has been reached, the specimen is exposed to
these conditions for the specified duration.
The relevant specification shall define the functioning of the specimen under test.
Low air velocity circulation is normally used for this test.
6 Test procedure
6.1 Confirmation of performance
IEC 60068-3-5 provides guidance for the confirmation of performance of temperature test
chambers. IEC 60068-3-1 provides general guidance for the performance of tests A and B.
The chamber shall be large enough compared with the size and amount of heat-dissipation of
the test sample.
6.2 Working space
The dimensions of the test sample shall be such that it is entirely within the working space of
the test chamber.
The temperature of the incident air delivered to the test specimen shall be within ± 2 K of test
severity temperature during the steady state conditions. The air temperature in the working
space shall be measured in accordance with Subclause 4.5.
NOTE 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 specified in the test report. The user should also specify the tolerance achieved at
temperatures above 315 °C.
6.3 Thermal radiation
The ability of the specimen to transfer heat by thermal radiation shall be minimised. This will
normally result in the screening of any heating or cooling elements from the specimen and
ensuring that parts of the chamber surfaces are not significantly different in temperature from
that of the conditioning air.
60068-2-2 © IEC:2007 – 13 –
6.4 Mounting
The thermal conduction and other relevant characteristics of the mounting and connections of
the test specimen should be specified in the relevant specification. When the test specimen is
intended for use with specific mounting devices, these shall be used for testing.
6.5 Severities
6.5.1 General
The severities, as indicated by temperature and duration of exposure, shall be prescribed by
the relevant specification. They shall be
a) chosen from the values given in 6.5.2 and 6.5.3; or
b) derived from the known environment if this gives significantly different values; or
c) derived from other known sources of relevant data (for example IEC 60721).
6.5.2 Temperature
+1 000 °C +250 °C +85 °C +45 °C
+800 °C +200 °C +70 °C +40 °C
+630 °C +175 °C +65 °C +35 °C
+500 °C +155 °C +60 °C +30 °C
+400 °C +125 °C +55 °C
+315 °C +100 °C +50 °C
6.5.3 Duration
2 h 72 h 168 h 336 h
16 h 96 h 240 h 1 000 h
When this testing procedure is used in connection with tests associated with endurance or
reliability, due note shall be taken of IEC publications which give particular recommendations
for durations for such tests.
6.6 Preconditioning
The relevant specification may call for a preconditioning.
6.7 Initial measurements
The initial state of the specimen shall be known. This may be achieved by visual inspection,
and/or functional tests as required by the relevant specification.
6.8 Conditioning
6.8.1 Steady state conditions
The specimen shall then be exposed to the high temperature conditions for the duration as
detailed in the relevant specification.
For the exceptional cases when the specimen does not achieve temperature stability, the
duration of the test commences at the time that the specimen is energised. Such cases are
typically caused by specimens having long duty cycles.

– 14 – 60068-2-2 © IEC:2007
6.8.2 Absolute humidity
The absolute humidity shall not exceed 20 g of water vapour per cubic metre of air
(corresponding to approximately 50 % relative humidity at 35 ºC) the relative humidity shall
not exceed 50 %.
6.9 Intermediate measurements
The relevant specification may call for loading and/or measurements during or at the end of
conditioning while the specimen is still in the chamber. If such measurements are required,
the relevant specification shall define the measurements and the period or periods after which
they shall be carried out. For these measurements, the specimen shall not be removed from
the chamber.
NOTE If it is desired to know the performance of the type of specimen before the end of the prescribed duration,
one additional lot will be required for each specified duration. Recovery and final measurements should be
performed separately for each lot.
6.10 Final temperature ramp
In case the specimen remains in operating or loaded conditions during the test, it shall be
switched off or unloaded before the temperature is lowered with the exception of test Be in
which the specimen shall remain operational throughout the recovery period.
At the end of the specified duration, the specimen shall remain in the chamber and the
temperature shall be gradually lowered to a value lying within the limits of standard
atmospheric conditions for testing. The rate of change of the temperature within the chamber
shall not exceed 1 K per minute, averaged over a period of not more than 5 min.
6.11 Recovery
The specimen shall be subjected to the recovery procedure in the chamber or otherwise as
appropriate.
The specimen shall then remain under standard atmospheric conditions for recovery for a
period adequate for the attainment of temperature stability, with a minimum of 1 h.
If required by the relevant specification, the specimen shall be switched on or loaded and
measured continuously during the recovery period.
If the standard conditions given above are not appropriate for the specimen to be tested, the
relevant specification may call for other recovery conditions.
6.12 Specimen with artificial cooling
The relevant specification shall define the characteristics of the coolant supplied to the
specimen. When the coolant is air, care shall be taken that the air is not contaminated by oil
and dry enough to avoid moisture problems.
6.13 Final measurements
The specimen shall be visually inspected and such performance checks as are required by
the relevant specification.
60068-2-2 © IEC:2007 – 15 –
7 Information to be given in the relevant specification
When this test is included in the relevant specification, the following details shall be given as
far as they are applicable:
a) preconditioning;
b) initial measurements;
c) details of mounting or supports;
d) state of specimen including cooling system during conditioning;
e) severity, temperature and duration of exposure;
f) the rate of change of temperature;
g) measurements and/or loading during conditioning;
h) recovery if non-standard;
i) final measurements;
j) any deviation in procedure as agreed upon between customer and supplier;
4.2).
k) temperature difference if low air velocity was not established (see Subclause
8 Information to be given in the test report
As a minimum, the test report shall show the following information:
1. Customer (name and address)
2. Test laboratory (name, address and details of
accreditation - if any)
3. Test dates
4. Type of test (Bb, Bd, or Be)
5. Purpose of test (development, qualification etc.)
6. Test standard, edition (IEC 60068-2-2, edition *)
7. Relevant laboratory test procedure (code and issue)
8. Test specimen description (unique id, drawing, photo, quantity build
status, etc.).
9. Test chamber identity (manufacturer, model number, unique id, etc.).
10. Performance of test apparatus (set point temperature control, air flow, etc.)
11. Air velocity and direction (air velocity and direction of incident air to the
specimen)
12. Uncertainties of measuring system
13. Calibration data (last and next due date)
14. Initial, intermediate and final
measurements
15. Required severities (from test specification)
16. Test severities (measuring points, data, etc.)
17. Performance of test specimens (results of functional tests, etc.)
18. Observations during testing and
actions taken
19. Summary of test
20. Distribution
NOTE A test log should be written for the testing which can be attached to the report.
___________
– 16 – 60068-2-2 © CEI:2007
SOMMAIRE
AVANT-PROPOS.18
INTRODUCTION.20

1 Domaine d’application .21
2 Références normatives.21
3 Termes et définitions .22
4 Application des essais de spécimens ne dissipant pas d’énergie par rapport aux
essais de spécimens dissipant de l’énergie .22
4.1 Généralités.22
4.2 Vérification de la haute ou faible vitesse de l’air dans la chambre d’essai .22
4.3 Application d’essais avec variation brusque de la température par rapport
aux essais avec variation lente de la température .23
4.4 Essai de spécimens dissipant de l’énergie.23
4.5 Surveillance de la température .23
4.6 Emballage .23
4.7 Représentations par diagrammes .23
5 Descriptions de l’essai.24
5.1 Généralités.24
5.2 Essai Bb: Chaleur sèche pour spécimens ne dissipant pas d’énergie avec
variation lente de la température .24
5.2.1 Objet .24
5.2.2 Description générale.25
5.3 Essai Bd: Chaleur sèche pour spécimens dissipant de l’énergie avec
variation lente de la température lorsqu’ils ne sont pas mis en
fonctionnement durant l’essai .25
5.3.1 Objet .25
5.3.2 Description générale.25
5.3.3 Recharge du spécimen .25
5.4 Essai Be: Chaleur sèche pour spécimens dissipant de d’énergie avec
variation lente de la température lorsqu’ils sont mis en fonctionnement
durant l’essai.25
5.4.1 Objet .25
5.4.2 Description générale.26
6 Procédure d’essai.26
6.1 Confirmation de performance .26
6.2 Espace de travail.26
6.3 Radiation thermique .26
6.4 Montage .27
6.5 Sévérités.27
6.5.1 Généralités.27
6.5.2 Température.27
6.5.3 Durée .27
6.6 Pré-conditionnement .27
6.7 Mesures initiales .27
6.8 Conditionnement .27
6.8.1 Conditions en régime continu .27
6.8.2 Humidité absolue.28
6.9 Mesures intermédiaires .28

60068-2-2 © CEI:2007 – 17 –
6.10 Rampe de température finale .28
6.11 Reprise .28
6.12 Spécimen avec refroidissement artificiel.28
6.13 Mesures finales .28
7 Renseignements que doit fournir la spécification particulière.29
8 Renseignements que doit fournir le rapport d’essai .29

Figure 1 – Diagramme complet des essais B: Chaleur sèche .24

– 18 – 60068-2-2 © CEI:2007
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
ESSAIS D’ENVIRONNEMENT –
Partie 2-2: Essais – Essai B: Chaleur sèche

AVANT-PROPOS
1) La Commission Electrotechnique Internationale (CEI) est une organisation mondiale de normalisation
composée de l'ensemble des comités électrotechniques nationaux (Comités nationaux de la CEI). La CEI a
pour objet de favoriser la coopération internationale pour toutes les questions de normalisation dans les
domaines de l'électricité et de l'électronique. A cet effet, la CEI – entre autres activités – publie des Normes
internationales, des Spécifications techniques, des Rapports techniques, des Spécifications accessibles au
public (PAS) et des Guides (ci-après dénommés "Publication(s) de la CEI"). Leur élaboration est confiée à des
comités d'études, aux travaux desquels tout Comité national intéressé par le sujet traité peut participer. Les
organisations internationales, gouvernementales et non gouvernementales, en liaison avec la CEI, participent
également aux travaux. La CEI collabore étroitement avec l'Organisation Internationale de Normalisation (ISO),
selon des conditions fixées par accord entre les deux organisations.
2) Les décisions ou accords officiels de la CEI concernant les questions techniques représentent, dans la mesure
du possible, un accord international sur les sujets étudiés, étant donné que les Comités nationaux de la CEI
intéressés sont représentés dans chaque comité d’études.
3) Les Publications de la CEI se présentent sous la forme de recommandations internationales et sont agréées
comme telles par les Comités
...