IEC 60721-2-3:2013

IEC 60721-2-3 ®
Edition 2.0 2013-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Classification of environmental conditions –
Part 2-3: Environmental conditions appearing in nature – Air pressure

Classification des conditions d'environnement –
Partie 2-3: Conditions d'environnement présentes dans la nature – Pression
atmosphérique
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IEC 60721-2-3 ®
Edition 2.0 2013-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Classification of environmental conditions –

Part 2-3: Environmental conditions appearing in nature – Air pressure

Classification des conditions d'environnement –

Partie 2-3: Conditions d'environnement présentes dans la nature – Pression

atmosphérique
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX H
ICS 19.040 ISBN 978-2-83220-875-5

– 2 – 60721-2-3 © IEC:2013
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Air pressure effects . 5
4.1 General . 5
4.2 Air pressure lower than normal . 5
4.3 Air pressure higher than normal . 6
5 Values of air pressure . 6
Bibliography . 8

Table 1 – Normal air pressure related to altitudes above and below sea-level . 6

60721-2-3 © IEC:2013 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CLASSIFICATION OF ENVIRONMENTAL CONDITIONS –

Part 2-3: Environmental conditions appearing in nature –
Air pressure
FOREWORD
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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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 60721-2-3 has been prepared by IEC technical committee 104:
Environmental conditions, classification and methods of test.
This second edition cancels and replaces the first edition, published in 1987, and constitutes
a technical revision.
The main changes with regard to the previous edition are as follows:
– removal of figures for decreasing cooling efficiency for altitude;
– simplification of Table 1;
– additional formula for calculating air pressure from altitude.

– 4 – 60721-2-3 © IEC:2013
The text of this standard is based on the following documents:
FDIS Report on voting
104/611/FDIS 104/615/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 publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60068 series, under the general title Classification of
environmental conditions, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability 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.
60721-2-3 © IEC:2013 – 5 –
CLASSIFICATION OF ENVIRONMENTAL CONDITIONS –

Part 2-3: Environmental conditions appearing in nature –
Air pressure
1 Scope
This part of IEC 60721 presents a selection of different values of air pressure appearing in
nature. It is intended to be used as part of the background material when selecting
appropriate severities of air pressure for product applications, which products are liable to be
exposed during storage, transportation and use.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60721-1, Classification of environmental conditions – Part 1: Environmental parameters
and their severities
3 Terms and definitions
Terms and definitions are defined, in context, throughout the present standard.
4 Air pressure effects
4.1 General
When selecting severities of the parameter air pressure for product application, the values
given in IEC 60721-1 should be applied.
Air pressure can affect products in various ways, the most important of which are as follows:
4.2 Air pressure lower than normal
Low air pressure occurring at altitudes above sea-level can affect products as follows:
– leakage of gases or fluids from gasket-sealed containers;
– rupture of pressurized containers;
– change of physical and chemical properties of low density materials;
– erratic operation or malfunction of equipment from arcing or corona as the breakdown
voltage between two electrodes in air decreases with pressure (the breakdown voltage of
air in a uniform electric field depends on the product of the gas pressure and the electrode
spacing for a given electrode shape and material (Paschen's law));
– decreased efficiency of heat dissipation by convection and conduction in air;
– acceleration of effects due essentially to temperature, for example volatilization of
plasticizers, evaporation of lubricants, etc.

– 6 – 60721-2-3 © IEC:2013
4.3 Air pressure higher than normal
High air pressure occurring in natural depressions and mines can have a mechanical effect on
sealed containers.
5 Values of air pressure
The normal value of air pressure at mean sea level is 101,325 kPa. Depending on meteo-
rological conditions, air pressure at sea level may vary. Similar variation occurs at altitudes
above and below sea-level.
In areas above sea-level, air pressure is lower than at sea level; in areas below sea level
(natural depressions and mines) it is higher than at sea-level.
Table
...