IEC 60068-2-78:2025

IEC 60068-2-78 ®
Edition 3.0 2025-08
INTERNATIONAL
STANDARD
REDLINE VERSION
Environmental testing -
Part 2-78: Tests - Test Cab: Damp heat, steady state
ICS 19.040; 29.020 ISBN 978-2-8327-0641-1
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or
by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either
IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC copyright
or have an enquiry about obtaining additional rights to this publication, please contact the address below or your local
IEC member National Committee for further information.

IEC Secretariat Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - IEC Products & Services Portal - products.iec.ch
webstore.iec.ch/advsearchform Discover our powerful search engine and read freely all the
The advanced search enables to find IEC publications by a publications previews, graphical symbols and the glossary.
variety of criteria (reference number, text, technical With a subscription you will always have access to up to date
committee, …). It also gives information on projects, content tailored to your needs.
replaced and withdrawn publications.
Electropedia - www.electropedia.org
The world's leading online dictionary on electrotechnology,
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published containing more than 22 500 terminological entries in English
details all new publications released. Available online and and French, with equivalent terms in 25 additional languages.
once a month by email. Also known as the International Electrotechnical Vocabulary
(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc
If you wish to give us your feedback on this publication or
need further assistance, please contact the Customer
Service Centre: sales@iec.ch.
CONTENTS
FOREWORD . 2
INTRODUCTION . 4
1 Scope and object . 5
2 Normative references . 5
3 Terms and definitions . 5
4 General test procedure . 5
4.1 General . 5
4.2 Description of test chamber and measuring system . 6
4.3 Severity . 7
4.4 Pre-conditioning . 8
4.5 Testing procedure . 9
4.6 Recovery procedure . 12
5 Measurements . 12
5.1 Initial measurements . 12
5.2 Intermediate measurements . 12
5.3 Final measurements. 12
6 Information to be given in the relevant specification . 12
7 Information to be given in the test report . 13
Bibliography . 14

Figure 1 – Examples of pre-conditioning phases with transition to the conditioning
periods for a) Method II and b) Method IV . 8
Figure 2 – Test Cab – Method I . 10
Figure 3 – Test Cab – Method II . 10
Figure 4 – Test Cab – Method III . 11
Figure 5 – Test Cab – Method IV . 11

Table 1 – Preferred values for the temperature and relative humidity . 7

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Environmental testing -
Part 2-78: Tests - Test Cab: Damp heat, steady state

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.
This redline version of the official IEC Standard allows the user to identify the changes made
to the previous edition IEC 60068-2-78:2012. A vertical bar appears in the margin wherever a
change has been made. Additions are in green text, deletions are in strikethrough red text.

IEC 60068-2-78 has been prepared by technical committee 104: Environmental conditions,
classification, and methods of test. It is an International Standard.
This third edition cancels and replaces the second edition published in 2012. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) revision of the requirements for the test chamber;
b) revision of the severities and including the dew point temperatures;
c) change of the temperature tolerances of the test to limits;
d) inclusion of a specified preconditioning procedure;
e) inclusion of a new figure for clarification purposes;
f) revision of standardized requirements for the test report.
The text of this International Standard is based on the following documents:
Draft Report on voting
104/1109/FDIS 104/1126/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 in 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.
INTRODUCTION
This part of IEC 60068 provides a test method of high humidity at constant temperature without
condensation on the specimen over a prescribed specified period. This test is performed to
evaluate the specimen as it is influenced by the absorption and diffusion of moisture and
moisture vapour.
1 Scope and object
This part of IEC 60068 establishes a test method for determining the ability of components or
equipment to withstand transportation, storage and use under conditions of high humidity.
The object of this document is to investigate the effect of high humidity at constant temperature
without condensation on a specimen over a prescribed specified period.
It is applicable to small equipment or components as well as large equipment, and can be
applied to both heat-dissipating and non-heat-dissipating 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 60068-1:2013, Environmental testing - Part 1: General and guidance
IEC 60068-2-67, Environmental testing - Part 2-67: Tests - Test Cy: Damp heat, steady state,
accelerated test primarily intended for components
IEC 60068-3-6, Environmental testing – Part 3-6: Supporting documentation and guidance –
Confirmation of the performance of temperature and humidity chambers
IEC Guide 104, The preparation of safety publications and the use of basic safety publications
and group safety publications
3 Terms and definitions
None.
For the purposes of this document, the terms and definitions given in IEC 60068-1 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
4 General test procedure
4.1 General
Test Cab can be applied to both heat-dissipating and non-heat-dissipating specimens.
The temperature and relative humidity limits given in this document are intended to take into
account errors in the measurement, slow changes of temperature, and temperature variations
of the working space.
NOTE 1 For further information on the working space, see IEC 60068-3-6.
The temperature and relative humidity refer to the control sensor of the test chamber, if not
specified otherwise.
The limits stated in this document do not take measurement uncertainty into consideration.
NOTE 2 These limits are valid for an empty test space during stabilized temperature/humidity conditions of the test.
In some conditions, where the specimen has a negligible impact on the chamber control, the limits can still be valid
for the chamber with specimen(s). For further information on the operation of a test chamber with specimens, see
IEC 60068-3-7.
NOTE 3 To maintain the relative humidity within the required limits, it can be necessary to keep the temperature
difference between any two points in the working space at any moment within narrower limits.
The dimensions of the test sample shall be such that it is entirely within the working space of
the test chamber. The specimen shall not be placed directly on the floor of the test chamber.
The position of the specimen shall be specified in the relevant specification.
4.2 Description of test chamber and measuring system
The temperature and humidity chamber shall be constructed and verified in accordance with
specifications IEC 60068-3-6.
The chamber and measuring system shall be such that
– sensing devices can be located in the working space to monitor the temperature and
humidity,
NOTE For heat-dissipating specimens, the temperature and humidity near the specimen may be influenced by
the effect of heat dissipation from the specimen.
– condensed water is drained from the chamber and not re-used unless purified,
– no condensed water from the walls and roof of the test chamber can fall on the specimen(s),
– water utilized to maintain humidity levels has electrical conductivity of not more than
20 µS/cm,
– the specimen under test shall not be subjected to radiant heat from the chamber conditioning
devices,
– injected moisture, when applicable, is injected remotely from the specimen and without
being directly on it,
– the volume of the test chamber is at least five times the total volume of the specimen under
test,
– a mounting device, when used, has minimum influence on the heat and humidity exchanges
between specimen and surrounding conditions, unless otherwise specified in the relevant
specification.
The chamber shall be so constructed that:
a) it can produce the temperature and relative humidity given in Table 1 for the requested time
duration;
a) the temperature and relative humidity in the working space can be maintained within the
limits given in Table 1 and 4.5;
b) the conditions prevailing at any point in the working space are uniform and are as similar as
possible to those prevailing in the immediate vicinity of suitably located temperature- and
humidity-sensing devices; the air in the chamber will therefore be continuously stirred at a
rate necessary to maintain the specified conditions of temperature and humidity;
c) the specimen under test is not subjected to radiant heat from the chamber conditioning
processes;
d) the water used for the chamber humidity system complies with the limits given in
IEC 60068-2-67;
e) any water is continuously drained from the chamber and not re-used unless purified;
f) the materials used in the construction do not cause any significant corrosion of the
specimen, or degradation of the quality of the humidifying water;
g) injected moisture, when applicable, is not directly applied to the specimen but injected
remotely from the specimen. Precautions shall be taken that no water droplets can deposit
on the specimen as a result of water injection.
Precautions should be taken to ensure that no condensed water from the walls and roof of the
test chamber can fall on the specimens. The specimen should not significantly impede the air
flow.
Where no specific mounting is specified, the thermal conduction of the mounting shall be low,
so that for all practical purposes the specimen is thermally isolated.
4.3 Severity
The test severity is defined by a combination of temperature, relative humidity and total test
duration. Temperature and relative humidity severities may be selected from the methods given
in Table 1, if not specified otherwise.
Table 1 – Preferred values for the temperature and relative humidity
Temperature Relative humidity
°C % RH
30 ± 2 93 ± 3
30 ± 2 85 ± 3
40 ± 2 93 ± 3
40 ± 2 85 ± 3
Method Temperature Relative humidity Dew point temperature
°C % RH °C
I 28 to 32 82 to 88 24,6 to 29,8
II 28 to 32 90 to 96 26,2 to 31,3
III 38 to 42 82 to 88 34,4 to 39,6
IV 38 to 42 90 to 96 36,1 to 41,2

Preferred test durations are 12 h, 16 h, 24 h, 2 days, 4 days, 10 days, 21 days or 56 days.
The total temperature tolerance of ± 2 K is intended to take account of absolute errors in the
measurement, slow changes of temperature and temperature variations of the working space.
However, in order to maintain the RH within the required tolerances, it is necessary to keep the
temperature difference between any two points in the working space at any moment within
narrower limits. The required humidity conditions will not be achieved if such temperature
differences exceed 1 K. It may also be necessary to keep short-term fluctuations within ± 0,5 K
to maintain the required humidity.
NOTE 1 As detailed in IEC 60068-1:2013, Annex A, this test is used to express component climatic category in the
third set of digits, which denotes the number of days of the damp heat, steady state test Ca.
NOTE 2 The dew point temperatures given in Table 1 are intended as an aid in order to be able to determine
whether condensation can have occurred during the test. If the specimen temperature exceeds the maximum dew
point temperature given in Table 1, the risk of condensation on the specimen can be considered minimal.
Condensation shall not occur on the specimen at any time during the test.
4.4 Pre-conditioning
The relevant specification may call for pre-conditioning.
The specimen shall be introduced into the test chamber either in the unpacked, switched-off,
ready-for-use state, or as otherwise specified in the relevant specification. The temperature of
the specimen shall be high enough to prevent condensation when the specimen is introduced
into the test chamber.
Condensation on the specimen shall always be avoided. Therefore, the specimen shall be
subjected to the temperature of the specified severity, i.e. 28 °C to 32 °C or 38 °C to 42 °C and
a relative humidity of 30 % RH or less for a period of 24 h prior to the test, if not specified
otherwise. Example of pre-conditioning phases for Method II and Method IV are given in
Figure 1.
a) example of pre-conditioning phase for b) example or pre-conditioning phase for
Method II Method IV
Figure 1 – Examples of pre-conditioning phases with transition to the conditioning
periods for a) Method II and b) Method IV
The pre-conditioning phase should be longer than 24 h, if the specimen temperature is still
lower than the dew point temperature applicable for the selected test condition (see Table 1).
If the specimen temperature reaches the pre-conditioning temperature within 24 h, the
pre-conditioning step may be terminated.
4.5 Testing procedure
The specimen shall be introduced into the chamber as required by the relevant specification.
The specimen shall be introduced in the unpacked, switched-off, ready-for-use state, or as
otherwise specified in the relevant specification.
In certain cases the relevant specification may allow the introduction of the specimen in the
chamber when this is already in the condition prescribed for the test; however, condensation
on the specimen shall always be avoided. This can be obtained for small specimens by pre-
heating them to the chamber temperature.
Adjust the temperature in the chamber to the prescribed severity. In order to avoid condensation
on the specimen, control the specimen temperature or allow the specimen to reach the
temperature first and then adjust the humidity in the chamber to the prescribed severity.
Adjust the humidity to the prescribed severity within a period of time of not more than 2 h.
Expose the specimen to the test conditions and duration as specified in the relevant
specification. The duration is measured from the time the specified conditions are achieved.
The relevant specification shall define the operating conditions and the period (or periods) in
which they shall be carried out.
After conditioning at the prescribed severity and before the final measurement, the recovery
procedure shall be followed.
Following the preconditioning procedure, the relative humidity in the test chamber shall be
raised to the relative humidity appropriate to the specified severity in a period of not more than
2 h.
The temperature and relative humidity shall then be maintained within the specified limits for a
duration as specified in the relevant specification. The duration shall commence as soon as the
conditions have stabilized. Figure 2 to Figure 5 show the test procedures with the preceding
stabilization periods according to Method I to Method IV.
The relevant specification shall define the operating conditions and the period (or periods) in
which they shall be carried out.
After conditioning at the specified severity and before the final measurement, the specimen
shall be subjected to the recovery procedure.
Figure 2 – Test Cab – Method I

Figure 3 – Test Cab – Method II
Figure 4 – Test Cab – Method III

Figure 5 – Test Cab – Method IV
4.6 Recovery procedure
The relevant specification shall prescribe the recovery method and duration. Recovery
conditions are described in IEC 60068-1.
At the end of the test, the specimen shall be subjected to the standard atmospheric conditions
for measurements and tests (see IEC 60068-1) for not less than 2 h and not more than 24 h, if
not specified otherwise.
5 Measurements
5.1 Initial measurements
Initial measurements should be performed under standard atmospheric conditions for
measurements and tests (see IEC 60068-1).
The specimen shall be visually inspected and electrically and mechanically checked, as
required by the relevant specification.
5.2 Intermediate measurements
The relevant specification may call for measurements during the test procedure while the
specimen is still in the chamber. If such measurements are required, the relevant specification
shall define the measurements and the period (periods) at which they shall be carried out. For
these measurements, the specimen shall not be removed from the chamber.
The relevant specification can require functional checks during conditioning.
Measurements preceded by a recovery, which would require removal of the specimens from the
test chamber, are not permissible during the conditioning. If it is desired to make intermediate
measurements, the relevant specification should define the measurements and the period(s)
during the conditioning after which they will be carried out.
5.3 Final measurements
The specimen shall be visually inspected and electrically and mechanically checked, as
required by the relevant
...

IEC 60068-2-78 ®
Edition 3.0 2025-08
NORME
INTERNATIONALE
Essais d'environnement -
Partie 2-78: Essais - Essai Cab: Chaleur humide, essai continu
ICS 19.040; 29.020 ISBN 978-2-8327-0618-3

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite ni
utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie et
les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Secretariat Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Recherche de publications IEC -  IEC Products & Services Portal - products.iec.ch
webstore.iec.ch/advsearchform Découvrez notre puissant moteur de recherche et consultez
La recherche avancée permet de trouver des publications gratuitement tous les aperçus des publications, symboles
IEC en utilisant différents critères (numéro de référence, graphiques et le glossaire. Avec un abonnement, vous aurez
texte, comité d’études, …). Elle donne aussi des toujours accès à un contenu à jour adapté à vos besoins.
informations sur les projets et les publications remplacées
ou retirées. Electropedia - www.electropedia.org
Le premier dictionnaire d'électrotechnologie en ligne au
IEC Just Published - webstore.iec.ch/justpublished monde, avec plus de 22 500 articles terminologiques en
Restez informé sur les nouvelles publications IEC. Just anglais et en français, ainsi que les termes équivalents
dans 25 langues additionnelles. Egalement appelé
Published détaille les nouvelles publications parues.
Disponible en ligne et une fois par mois par email. Vocabulaire Electrotechnique International (IEV) en ligne.

Service Clients - webstore.iec.ch/csc
Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-
nous: sales@iec.ch.
SOMMAIRE
AVANT-PROPOS . 2
INTRODUCTION . 4
1 Domaine d'application . 5
2 Références normatives . 5
3 Termes et définitions . 5
4 Procédure d'essai générale . 5
4.1 Généralités . 5
4.2 Description de la chambre d'essai . 6
4.3 Sévérité . 6
4.4 Préconditionnement . 7
4.5 Procédure d'essai . 8
4.6 Procédure de reprise . 11
5 Mesurages. 11
5.1 Mesurages initiaux . 11
5.2 Mesurages intermédiaires . 11
5.3 Mesurages finaux. 11
6 Renseignements à fournir dans la spécification applicable . 11
7 Renseignements à fournir dans le rapport d'essai . 12
Bibliographie . 13

Figure 1 – Exemples de phases de préconditionnement avec transition vers les
périodes d'épreuve pour a) la Méthode II et b) la Méthode IV . 8
Figure 2 – Essai Cab – Méthode I . 9
Figure 3 – Essai Cab – Méthode II . 9
Figure 4 – Essai Cab – Méthode III . 10
Figure 5 – Cab – Méthode IV . 10

Tableau 1 – Valeurs préférentielles pour la température et l'humidité relative . 7

COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
Essais d'environnement -
Partie 2-78: Essais - Essai Cab: Chaleur humide, essai continu

AVANT-PROPOS
1) La Commission Électrotechnique Internationale (IEC) est une organisation mondiale de normalisation composée
de l'ensemble des comités électrotechniques nationaux (Comités nationaux de l'IEC). L'IEC a pour objet
de favoriser la coopération internationale pour toutes les questions de normalisation dans les domaines
de l'électricité et de l'électronique. À cet effet, l'IEC – 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 l'IEC"). 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 l'IEC, participent également
aux travaux. L'IEC 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 l'IEC concernant les questions techniques représentent, dans la mesure
du possible, un accord international sur les sujets étudiés, étant donné que les Comités nationaux de l'IEC
intéressés sont représentés dans chaque comité d'études.
3) Les Publications de l'IEC se présentent sous la forme de recommandations internationales et sont agréées
comme telles par les Comités nationaux de l'IEC. Tous les efforts raisonnables sont entrepris afin que l'IEC
s'assure de l'exactitude du contenu technique de ses publications; l'IEC ne peut pas être tenue responsable
de l'éventuelle mauvaise utilisation ou interprétation qui en est faite par un quelconque utilisateur final.
4) Dans le but d'encourager l'uniformité internationale, les Comités nationaux de l'IEC s'engagent,
dans toute la mesure possible, à appliquer de façon transparente les Publications de l'IEC dans leurs publications
nationales et régionales. Toutes divergences entre toutes Publications de l'IEC et toutes publications nationales
ou régionales correspondantes doivent être indiquées en termes clairs dans ces dernières.
5) L'IEC elle-même ne fournit aucune attestation de conformité. Des organismes de certification indépendants
fournissent des services d'évaluation de conformité et, dans certains secteurs, accèdent aux marques
de conformité de l'IEC. L'IEC n'est responsable d'aucun des services effectués par les organismes de certification
indépendants.
6) Tous les utilisateurs doivent s'assurer qu'ils sont en possession de la dernière édition de cette publication.
7) Aucune responsabilité ne doit être imputée à l'IEC, à ses administrateurs, employés, auxiliaires ou mandataires,
y compris ses experts particuliers et les membres de ses comités d'études et des Comités nationaux de l'IEC,
pour tout préjudice causé en cas de dommages corporels et matériels, ou de tout autre dommage de quelque
nature que ce soit, directe ou indirecte, ou pour supporter les coûts (y compris les frais de justice) et les dépenses
découlant de la publication ou de l'utilisation de cette Publication de l'IEC ou de toute autre Publication de l'IEC,
ou au crédit qui lui est accordé.
8) L'attention est attirée sur les références normatives citées dans cette publication. L'utilisation de publications
référencées est obligatoire pour une application correcte de la présente publication.
9) L'IEC attire l'attention sur le fait que la mise en application du présent document peut entraîner l'utilisation d'un ou
de plusieurs brevets. L'IEC ne prend pas position quant à la preuve, à la validité et à l'applicabilité de tout droit
de brevet revendiqué à cet égard. À la date de publication du présent document, l'IEC n'avait pas reçu notification
qu'un ou plusieurs brevets pouvaient être nécessaires à sa mise en application. Toutefois, il y a lieu d'avertir
les responsables de la mise en application du présent document que des informations plus récentes
sont susceptibles de figurer dans la base de données de brevets, disponible à l'adresse https://patents.iec.ch.
L'IEC ne saurait être tenue pour responsable de ne pas avoir identifié de tels droits de brevets.
L'IEC 60068-2-78 a été établie par le comité d'études 104 de l'IEC: Conditions, classification et
essais d'environnement. Il s'agit d'une Norme internationale.
Cette troisième édition annule et remplace la deuxième édition parue en 2012. Cette édition
constitue une révision technique.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition
précédente:
a) révision des exigences relatives à la chambre d'essai;
b) révision des sévérités et ajout des températures de point de rosée;
c) remplacement des tolérances sur la température de l'essai par des limites;
d) ajout d'une procédure spécifiée de préconditionnement;
e) ajout d'une nouvelle figure à des fins de clarification;
f) révision des exigences normatives relatives au rapport d'essai.
Le texte de cette Norme internationale est issu des documents suivants:
Projet Rapport de vote
104/1109/FDIS 104/1126/RVD
Le rapport de vote indiqué dans le tableau ci-dessus donne toute information sur le vote ayant
abouti à son approbation.
La langue employée pour l'élaboration de cette Norme internationale est l'anglais.
Ce document a été rédigé selon les Directives ISO/IEC, Partie 2, il a été développé
selon les Directives ISO/IEC, Partie 1 et les Directives ISO/IEC, Supplément IEC, disponibles
sous www.iec.ch/members_experts/refdocs. Les principaux types de documents développés
par l'IEC sont décrits plus en détail sous www.iec.ch/publications.
Une liste de toutes les parties de la série IEC 60068, sous le titre général Essais
d'environnement, se trouve sur le site web de l'IEC.
Le comité a décidé que le contenu de ce document ne sera pas modifié avant la date de stabilité
indiquée sur le site web de l'IEC sous webstore.iec.ch dans les données relatives au document
recherché. À cette date, le document sera
• reconduit,
• supprimé, ou
• révisé.
INTRODUCTION
La présente partie de l'IEC 60068 fournit une méthode d'essai de forte humidité à température
constante, sans condensation sur le spécimen, sur une période spécifiée. Cet essai est réalisé
pour évaluer le spécimen lorsqu'il est influencé par l'absorption et la diffusion d'humidité et
de vapeur d'humidité.
1 Domaine d'application
La présente partie de l'IEC 60068 établit une méthode d'essai en vue de déterminer la capacité
des composants ou des équipements à supporter le transport, le stockage et l'utilisation
dans des conditions de forte humidité.
L'objet du présent document est de rechercher l'effet d'une forte humidité à température
constante sans condensation sur un spécimen, au cours d'une période spécifiée.
Il s'applique aussi bien aux équipements ou composants de petite taille qu'aux équipements
volumineux et peut être appliqué à la fois à des spécimens dissipateurs de chaleur et
non dissipateurs de chaleur.
2 Références normatives
Les documents suivants sont cités dans le texte de sorte qu'ils constituent, pour tout ou partie
de leur contenu, des exigences du présent document. Pour les références datées,
seule l'édition citée s'applique. Pour les références non daté
...

IEC 60068-2-78 ®
Edition 3.0 2025-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing -
Part 2-78: Tests - Test Cab: Damp heat, steady state

Essais d'environnement -
Partie 2-78: Essais - Essai Cab: Chaleur humide, essai continu
ICS 19.040, 29.020 ISBN 978-2-8327-0618-3

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or
by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either
IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC copyright
or have an enquiry about obtaining additional rights to this publication, please contact the address below or your local
IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite ni
utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie et
les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Secretariat Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - IEC Products & Services Portal - products.iec.ch
webstore.iec.ch/advsearchform Discover our powerful search engine and read freely all the
The advanced search enables to find IEC publications by a publications previews, graphical symbols and the glossary.
variety of criteria (reference number, text, technical With a subscription you will always have access to up to date
committee, …). It also gives information on projects, content tailored to your needs.

replaced and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published containing more than 22 500 terminological entries in English
details all new publications released. Available online and and French, with equivalent terms in 25 additional languages.
once a month by email. Also known as the International Electrotechnical Vocabulary
(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc
If you wish to give us your feedback on this publication or
need further assistance, please contact the Customer
Service Centre: sales@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Recherche de publications IEC -  IEC Products & Services Portal - products.iec.ch
webstore.iec.ch/advsearchform Découvrez notre puissant moteur de recherche et consultez
La recherche avancée permet de trouver des publications gratuitement tous les aperçus des publications, symboles
IEC en utilisant différents critères (numéro de référence, graphiques et le glossaire. Avec un abonnement, vous aurez
texte, comité d’études, …). Elle donne aussi des toujours accès à un contenu à jour adapté à vos besoins.
informations sur les projets et les publications remplacées
ou retirées. Electropedia - www.electropedia.org
Le premier dictionnaire d'électrotechnologie en ligne au
IEC Just Published - webstore.iec.ch/justpublished monde, avec plus de 22 500 articles terminologiques en
Restez informé sur les nouvelles publications IEC. Just anglais et en français, ainsi que les termes équivalents
Published détaille les nouvelles publications parues. dans 25 langues additionnelles. Egalement appelé
Disponible en ligne et une fois par mois par email. Vocabulaire Electrotechnique International (IEV) en ligne.

Service Clients - webstore.iec.ch/csc
Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-
nous: sales@iec.ch.
CONTENTS
FOREWORD . 2
INTRODUCTION . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 General test procedure . 5
4.1 General . 5
4.2 Description of test chamber . 6
4.3 Severity . 6
4.4 Pre-conditioning . 7
4.5 Testing procedure . 8
4.6 Recovery procedure . 10
5 Measurements . 10
5.1 Initial measurements . 10
5.2 Intermediate measurements . 10
5.3 Final measurements. 11
6 Information to be given in the relevant specification . 11
7 Information to be given in the test report . 11
Bibliography . 13

Figure 1 – Examples of pre-conditioning phases with transition to the conditioning
periods for a) Method II and b) Method IV . 7
Figure 2 – Test Cab – Method I . 8
Figure 3 – Test Cab – Method II . 9
Figure 4 – Test Cab – Method III . 9
Figure 5 – Test Cab – Method IV . 10

Table 1 – Preferred values for the temperature and relative humidity . 6

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Environmental testing -
Part 2-78: Tests - Test Cab: Damp heat, steady state

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 60068-2-78 has been prepared by technical committee 104: Environmental conditions,
classification, and methods of test. It is an International Standard.
This third edition cancels and replaces the second edition published in 2012. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) revision of the requirements for the test chamber;
b) revision of the severities and including the dew point temperatures;
c) change of the temperature tolerances of the test to limits;
d) inclusion of a specified preconditioning procedure;
e) inclusion of a new figure for clarification purposes;
f) revision of standardized requirements for the test report.
ext of this International Standard is based on the following documents:
The t
Draft Report on voting
104/1109/FDIS 104/1126/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 in 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.
INTRODUCTION
This part of IEC 60068 provides a test method of high humidity at constant temperature without
condensation on the specimen over a specified period. This test is performed to evaluate the
specimen as it is influenced by the absorption and diffusion of moisture and moisture vapour.

1 Scope
This part of IEC 60068 establishes a test method for determining the ability of components or
equipment to withstand transportation, storage and use under conditions of high humidity.
The object of this document is to investigate the effect of high humidity at constant temperature
without condensation on a specimen over a specified period.
It is applicable to small equipment or components as well as large equipment and can be applied
to both heat-dissipating and non-heat-dissipating 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 60068-1:2013, Environmental testing - Part 1: General and guidance
IEC 60068-2-67, Environmental testing - Part 2-67: Tests - Test Cy: Damp heat, steady state,
accelerated test primarily intended for components
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60068-1 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
4 General test procedure
4.1 General
Test Cab can be applied to both heat-dissipating and non-heat-dissipating specimens.
The temperature and relative humidity limits given in this document are intended to take into
account errors in the measurement, slow changes of temperature, and temperature variations
of the working space.
NOTE 1 For further information on the working space, see IEC 60068-3-6.
The temperature and relative humidity refer to the control sensor of the test chamber, if not
specified otherwise.
The limits stated in this document do not take measurement uncertainty into consideration.
NOTE 2 These limits are valid for an empty test space during stabilized temperature/humidity conditions of the test.
In some conditions, where the specimen has a negligible impact on the chamber control, the limits can still be valid
for the chamber with specimen(s). For further information on the operation of a test chamber with specimens, see
IEC 60068-3-7.
NOTE 3 To maintain the relative humidity within the required limits, it can be necessary to keep the temperature
difference between any two points in the working space at any moment within narrower limits.
The dimensions of the test sample shall be such that it is entirely within the working space of
the test chamber. The specimen shall not be placed directly on the floor of the test chamber.
The position of the specimen shall be specified in the relevant specification.
4.2 Description of test chamber
The chamber shall be so constructed that:
a) it can produce the temperature and relative humidity given in Table 1 for the requested time
duration;
b) the temperature and relative humidity in the working space can be maintained within the
limits given in Table 1 and 4.5;
c) the conditions prevailing at any point in the working space are uniform and are as similar as
possible to those prevailing in the immediate vicinity of suitably located temperature- and
humidity-sensing devices; the air in the chamber will therefore be continuously stirred at a
rate necessary to maintain the specified conditions of temperature and humidity;
d) the specimen under test is not subjected to radiant heat from the chamber conditioning
processes;
e) the water used for the chamber humidity system complies with the limits given in
IEC 60068-2-67;
f) any water is continuously drained from the chamber and not re-used unless purified;
g) the materials used in the construction do not cause any significant corrosion of the
specimen, or degradation of the quality of the humidifying water;
h) injected moisture, when applicable, is not directly applied to the specimen but injected
remotely from the specimen. Precautions shall be taken that no water droplets can deposit
on the specimen as a result of water injection.
Precautions should be taken to ensure that no condensed water from the walls and roof of the
test chamber can fall on the specimens. The specimen should not significantly impede the air
flow.
Where no specific mounting is specified, the thermal conduction of the mounting shall be low,
so that for all practical purposes the specimen is thermally isolated.
4.3 Severity
The test severity is defined by a combination of temperature, relative humidity and total test
duration. Temperature and relative humidity severities may be selected from the methods given
in Table 1, if not specified otherwise.
Table 1 – Preferred values for the temperature and relative humidity
Method Temperature Relative humidity Dew point temperature
°C % RH °C
I 28 to 32 82 to 88 24,6 to 29,8
II 28 to 32 90 to 96 26,2 to 31,3
III 38 to 42 82 to 88 34,4 to 39,6
IV 38 to 42 90 to 96 36,1 to 41,2

Preferred test durations are 12 h, 16 h, 24 h, 2 days, 4 days, 10 days, 21 days or 56 days.
NOTE 1 As detailed in IEC 60068-1:2013, Annex A, this test is used to express component climatic category in the
third set of digits, which denotes the number of days of the damp heat, steady state test Ca.
NOTE 2 The dew point temperatures given in Table 1 are intended as an aid in order to be able to determine
whether condensation can have occurred during the test. If the specimen temperature exceeds the maximum dew
point temperature given in Table 1, the risk of condensation on the specimen can be considered minimal.
Condensation shall not occur on the specimen at any time during the test.
4.4 Pre-conditioning
The specimen shall be introduced into the test chamber either in the unpacked, switched-off,
ready-for-use state, or as otherwise specified in the relevant specification. The temperature of
the specimen shall be high enough to prevent condensation when the specimen is introduced
into the test chamber.
Condensation on the specimen shall always be avoided. Therefore, the specimen shall be
subjected to the temperature of the specified severity, i.e. 28 °C to 32 °C or 38 °C to 42 °C and
a relative humidity of 30 % RH or less for a period of 24 h prior to the test, if not specified
otherwise. Example of pre-conditioning phases for Method II and Method IV are given in
Figure 1.
a) example of pre-conditioning phase for b) example or pre-conditioning phase for
Method II Method IV
Figure 1 – Examples of pre-conditioning phases with transition to the conditioning
periods for a) Method II and b) Method IV
The pre-conditioning phase should be longer than 24 h, if the specimen temperature is still
lower than the dew point temperature applicable for the selected test condition (see Table 1).
If the specimen temperature reaches the pre-conditioning temperature within 24 h, the
pre-conditioning step may be terminated.
4.5 Testing procedure
Following the preconditioning procedure, the relative humidity in the test chamber shall be
raised to the relative humidity appropriate to the specified severity in a period of not more than
2 h.
The temperature and relative humidity shall then be maintained within the specified limits for a
duration as specified in the relevant specification. The duration shall commence as soon as the
conditions have stabilized. Figure 2 to Figure 5 show the test procedures with the preceding
stabilization periods according to Method I to Method IV.
The relevant specification shall define the operating conditions and the period (or periods) in
which they shall be carried out.
After conditioning at the specified severity and before the final measurement, the specimen
shall be subjected to the recovery procedure.

Figure 2 – Test Cab – Method I
Figure 3 – Test Cab – Method II

Figure 4 – Test Cab – Method III
Figure 5 – Test Cab – Method IV
4.6 Recovery procedure
At the end of the test, the specimen shall be subjected to the standard atmospheric conditions
for measurements and tests (see IEC 60068-1) for not less than 2 h and not more than 24 h, if
not specified otherwise.
5 Measurements
5.1 Initial measurements
Initial measurements should be performed under standard atmospheric conditions for
measurements and tests (see IEC 60068-1).
The specimen shall be visually inspected and electrically and mechanically checked, as
required by the relevant specification.
5.2 Intermediate measurements
The relevant specification can require functional checks during conditioning.
Measurements preceded by a recovery, which would require removal of the specimens from the
test chamber, are not permissible during the conditioning. If it is desired to make intermediate
measurements, the relevant specification should define the measurements and the period(s)
during the conditioning after which they will be carried out.
5.3 Final measurements
The specimen shall be visually inspected and electrically and mechanically checked, as
required by the relevant specification.
If the initial measurements were made under conditions other than standard atmospheric
conditions for measurement and test, the same conditions shall be used for both sets of
measurements.
6 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 (unpowered, powered, packaged, unpackaged, etc.);
e) type of specimen – heat dissipating or non-heat dissipating;
f) test severities and limits
1) temperature,
2) relative humidity,
3) duration;
g) intermediate measurements;
h) recovery procedure;
i) final measurements;
j) any deviation in procedure as agreed upon between customer and supplier.
7 Information to be given in the test report
As a minimum, the test report shall contain the following information. Items shown in
parentheses are examples.
a) customer (name and address);
b) test laboratory (name and address and details of accreditation – if any);
c) test dates (dates when test was run);
d) type of test (Cab);
e) test standard, edition (IEC 60068-2-78:edition used);
f) test specimen description (drawing, photo, quantity, build status, etc.);
g) test chamber identity (manufacturer, model number, unique identification, etc.);
h) test setup (details of mounting and supports, measuring points, etc.);
i) initial, intermediate and final measurements (if performed by the test laboratory);
j) required severities (from relevant specification);
k) test severities (preconditioning, temperatures, test duration, etc.);
l) performance of test specimens (results of functional tests, etc.);
m) observations during testing and actions taken (any pertinent observations);
n) test results (test summary, e.g. pass/fail decision).
---------------------- Pa
...