IEC 60079-10-1:2008

Explosive atmospheres - Part 10-1: Classification of areas - Explosive gas atmospheres

IEC 60079-10-1:2008 is concerned with the classification of areas where flammable gas or vapour or mist hazards may arise and may then be used as a basis to support the proper selection and installation of equipment for use in a hazardous area. It is intended to be applied where there may be an ignition hazard due to the presence of flammable gas or vapour, mixed with air under normal atmospheric conditions, but it does not apply to
a) mines susceptible to firedamp;
b) the processing and manufacture of explosives;
c) areas where a hazard may arise due to the presence of combustible dusts or fibres;
d) catastrophic failures which are beyond the concept of abnormality;
e) rommos used for medial purposes;
f) domestic premises.
This first edition of IEC 60079-10-1 cancels and replaces the fourth edition of IEC 60079-10, published in 2002, and constitutes a technical revision. The significant technical changes with respect to the previous edition are:
- introduction of Annex D which deals with explosion hazard from flammable mists generated by the release under pressure of high flash point liquids;
- introduction of Clause A.3 (release rate) which gives thermodynamic equations for release rate with a number of examples for estimating release rate of fluids and gases.

Atmosphères explosives - Partie 10-1: Classement des emplacements - Atmosphères explosives gazeuses

La CEI 60079-10-1:2008 est relative au classement des emplacements dans lesquels des risques dus à des gaz, vapeurs ou brouillards inflammables peuvent apparaître, et ainsi constituer une base pour le choix et l'installation corrects du matériel utilisé dans de tels emplacements. Elle est destinée à être appliquée là où il peut exister un danger d'inflammation du fait de la présence de gaz ou vapeurs inflammables, en mélange avec l'air, dans les conditions atmosphériques normales; mais elle ne s'applique pas:
a) aux mines grisouteuses;
b) au traitement et à la fabrication des explosifs;
c) aux emplacements dans lesquels un danger dû à la présence de poussières ou fibres inflammables peut apparaître;
d) aux défaillances catastrophiques, qui dépassent le concept d'anormalité traité dans la présente norme;
e) aux locaux utilisés à des fins médicales;
f) aux locaux à usage domestique.
Cette première édition de la CEI 60079-10-1 annule et remplace la quatrième édition de la CEI 60079-10, publiée en 2002, et constitue une révision technique. Les principales modifications techniques suivantes ont été apportées par rapport à l'édition précédente:
- introduction de l'Annexe D qui traite du danger d'explosion du brouillard inflammable généré par l'échappement sous pression de liquides au point d'éclair élevé;
- introduction de l'Article A.3 (taux de dégagement) qui donne des équations thermodynamiques pour le taux de dégagement avec des exemples pour l'estimation du taux de dégagement des fluides et de gaz.

General Information

• Status: Published
• Publication Date: 08-Dec-2008
• ICS: 29.260.20 - Electrical apparatus for explosive atmospheres
• Technical Committee: SC 31J - Classification of hazardous areas and installation requirements
• Drafting Committee: MT 60079-10-1 - TC 31/SC 31J/MT 60079-10-1
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 08-Sep-2015

Relations

• Revised: IEC 60079-10-1:2015 - Explosive atmospheres - Part 10-1: Classification of areas - Explosive gas atmospheres
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 60079-10-1
Edition 1.0 2008-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE


Explosive atmospheres –
Part 10-1: Classification of areas – Explosive gas atmospheres

Atmosphères explosives –
Partie 10-1: Classement des emplacements – Atmosphères explosives gazeuses

IEC 60079-10-1:2008

---------------------- Page: 1 ----------------------
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IEC 60079-10-1
Edition 1.0 2008-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE


Explosive atmospheres –
Part 10-1: Classification of areas – Explosive gas atmospheres

Atmosphères explosives –
Partie 10-1: Classement des emplacements – Atmosphères explosives gazeuses

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
XB
CODE PRIX
ICS 29.260.20 ISBN 978-2-88910-043-9
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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CONTENTS
FOREWORD.3
INTRODUCTION.5
1 Scope.6
2 Normative references .7
3 Terms and definitions .7
4 General .10
4.1 Safety principles.10
4.2 Area classification objectives .11
5 Area classification procedure.12
5.1 General .12
5.2 Sources of release .12
5.3 Type of zone .13
5.4 Extent of zone .13
5.4.1 Release rate of gas or vapour.13
5.4.2 Lower explosive limit (LEL).14
5.4.3 Ventilation .14
5.4.4 Relative density of the gas or vapour when it is released.15
5.4.5 Other parameters to be considered.15
5.4.6 Illustrative examples.15
6 Ventilation .16
6.1 General .16
6.2 Main types of ventilation.16
6.3 Degree of ventilation .16
6.4 Availability of ventilation.17
7 Documentation .17
7.1 General .17
7.2 Drawings, data sheets and tables.17
Annex A (informative) Examples of sources of release and release rate .18
Annex B (informative) Ventilation.24
Annex C (informative) Examples of hazardous area classification .40
Annex D (informative) Flammable mists .63
Bibliography.65

Figure C.1 – Preferred symbols for hazardous area zones .41
Figure C.2 – Schematic approach to the classification of hazardous areas.62

Table A.1 – Effect of openings on grade of release .19
Table B.1 – Influence of independent ventilation on type of zone .31
Table B.2 – Procedure for summation of multiple releases within location V .32
o
Table B.3 – Procedure for summation of multiple primary grade releases .32
Table C.1 − Hazardous area classification data sheet – Part I: Flammable material list
and characteristics.60
Table C.2 − Hazardous area classification data sheet − Part II: List of sources of
release .61

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60079-10-1 © IEC:2008 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

EXPLOSIVE ATMOSPHERES –

Part 10-1: Classification of areas –
Explosive gas atmospheres


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,
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Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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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.
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60079-10-1 has been prepared by subcommittee 31J:
Classification of hazardous areas and installation requirements, of IEC technical committee
31: Equipment for explosive atmospheres.
This first edition of IEC 60079-10-1 cancels and replaces the fourth edition of IEC 60079-10,
published in 2002, and constitutes a technical revision.
The significant technical changes with respect to the previous edition are as follows:
• Introduction of Annex D which deals with explosion hazard from flammable mists
generated by the release under pressure of high flash point liquids.
• Introduction of Clause A.3 (release rate) which gives thermodynamic equations for release
rate with a number of examples for estimating release rate of fluids and gases.

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The text of this standard is based on the following documents:
FDIS Report on voting
31J/159/FDIS 31J/160/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 of the IEC 60079 series, under the general title Explosive atmospheres, 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.

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60079-10-1 © IEC:2008 – 5 –
INTRODUCTION
In areas where dangerous quantities and concentrations of flammable gas or vapour may
arise, protective measures are to be applied in order to reduce the risk of explosions. This
part of IEC 60079 sets out the essential criteria against which the ignition hazards can be
assessed, and gives guidance on the design and control parameters which can be used in
order to reduce such a hazard.

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EXPLOSIVE ATMOSPHERES –

Part 10-1: Classification of areas –
Explosive gas atmospheres



1 Scope
This part of IEC 60079 is concerned with the classification of areas where flammable gas or
vapour or mist hazards (see Notes 1, 2 and 3) may arise and may then be used as a basis to
support the proper selection and installation of equipment for use in a hazardous area.
It is intended to be applied where there may be an ignition hazard due to the presence of
flammable gas or vapour, mixed with air under normal atmospheric conditions (see Note 4),
but it does not apply to
a) mines susceptible to firedamp;
b) the processing and manufacture of explosives;
c) areas where a hazard may arise due to the presence of combustible dusts or fibres (refer
to IEC 61241-10 / IEC 60079-10-2);
d) catastrophic failures which are beyond the concept of abnormality dealt with in this
standard (see Note 5);
e) rooms used for medical purposes;
f) domestic premises.
This standard does not take into account the effects of consequential damage.
Definitions and explanations of terms are given together with the main principles and
procedures relating to hazardous area classification.
For detailed recommendations regarding the extent of the hazardous areas in specific
industries or applications, reference may be made to national or industry codes relating to
those applications.
NOTE 1 Flammable mists may form or be present at the same time as flammable vapours. Liquids not considered
to be hazardous in terms of this standard (due to the flash point), when released under pressure may also generate
flammable mists. In such cases, the strict application of area classification for gases and vapours may not be
appropriate as the basis for selection of equipment.
Information on flammable mists is provided in Annex D.
NOTE 2 The use of IEC 60079-14 for selection of equipment and installations is not required for mist hazards.
NOTE 3 For the purpose of this standard, an area is a three-dimensional region or space.
NOTE 4 Atmospheric conditions include variations above and below reference levels of 101,3 kPa (1 013 mbar)
and 20 °C (293 K), provided that the variations have a negligible effect on the explosion properties of the
flammable materials.
NOTE 5 Catastrophic failure in this context is applied, for example, to the rupture of a process vessel or pipeline
and events that are not predictable.
NOTE 6 In any process plant, irrespective of size, there may be numerous sources of ignition apart from those
associated with equipment. Appropriate precautions will be necessary to ensure safety in this context. This
standard may be used with judgement for other ignition sources.

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60079-10-1 © IEC:2008 – 7 –
2 Normative references
The following referenced documents are indispensable for the application 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 60050-426, International Electrotechnical Vocabulary (IEV) – Part 426: Equipment for
explosive atmospheres
IEC 60079-0, Explosive atmospheres – Part 0: Equipment – General requirements
IEC 60079-4, Electrical apparatus for explosive gas atmospheres – Part 4: Method of test for
ignition temperature
IEC 60079-4A, First supplement to IEC 60079-4 (1966), Electrical apparatus for explosive gas
atmospheres – Part 4: Method of test for ignition temperature
IEC 60079-20, Electrical apparatus for explosive gas atmospheres – Part 20: Data for
flammable gases and vapours, relating to the use of electrical apparatus
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60079-0 and the
following apply.
NOTE Additional definitions applicable to explosive atmospheres can be found in the IEC 60050-426.
3.1
explosive atmosphere
mixture with air, under atmospheric conditions, of flammable substances in the form of gas,
vapour, dust, fibres, or flyings which, after ignition, permits self-sustaining propagation
[IEC 60079-0, definition 3.22]
3.2
explosive gas atmosphere
mixture with air, under atmospheric conditions, of flammable substances in the form of gas or
vapour, which, after ignition, permits self-sustaining flame propagation
[IEC 60079-0, definition 3.24]
NOTE 1 Although a mixture which has a concentration above the upper explosive limit (UEL) is not an explosive
gas atmosphere, it can readily become so and, in certain cases for area classification purposes, it is advisable to
consider it as an explosive gas atmosphere.
NOTE 2 There are some gases which are explosive with the concentration of 100 %.
3.3
hazardous area (on account of explosive gas atmospheres)
an area in which an explosive gas atmosphere is or may be expected to be present, in
quantities such as to require special precautions for the construction, installation and use of
equipment
3.4
non-hazardous area (on account of explosive gas atmospheres)
an area in which an explosive gas atmosphere is not expected to be present in quantities
such as to require special precautions for the construction, installation and use of equipment

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3.5
zones
hazardous areas are classified into zones based upon the frequency of the occurrence and
duration of an explosive gas atmosphere, as follows:
3.6
zone 0
an area in which an explosive gas atmosphere is present continuously or for long periods or
frequently
3.7
zone 1
an area in which an explosive gas atmosphere is likely to occur in normal operation
occasionally
3.8
zone 2
area in which an explosive gas atmosphere is not likely to occur in normal operation but, if it
does occur, will persist for a short period only
[IEV 426-03-05]
NOTE Indications of the frequency of the occurrence and duration may be taken from codes relating to specific
industries or applications.
3.9
source of release
a point or location from which a gas, vapour, mist or liquid may be released into the
atmosphere so that an explosive gas atmosphere could be formed
IEV 426-03-06, modified]
3.10
grades of release
there are three basic grades of release, as listed below in order of decreasing frequency and
likelihood of the explosive gas atmosphere being present:
a) continuous grade;
b) primary grade;
c) secondary grade.
A source of release may give rise to any one of these grades of release, or to a combination
of more than one
3.11
continuous grade of release
release which is continuous or is expected to occur frequently or for long periods
3.12
primary grade of release
release which can be expected to occur periodically or occasionally during normal operation
3.13
secondary grade of release
release which is not expected to occur in normal operation and, if it does occur, is likely to do
so only infrequently and for short periods

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60079-10-1 © IEC:2008 – 9 –
3.14
release rate
quantity of flammable gas, vapour or mist emitted per unit time from the source of release
3.15
normal operation
situation when the equipment is operating within its designed parameters
NOTE 1 Minor releases of flammable material may be part of normal operation. For example, releases from seals
which rely on wetting by the fluid which is being pumped are considered to be minor releases.
NOTE 2 Failures (such as the breakdown of pump seals, flange gaskets or spillages caused by accidents) which
involve urgent repair or shut-down are not considered to be part of normal operation nor are they considered to be
catastrophic.
NOTE 3 Normal operation includes start-up and shut-down conditions.
3.16
ventilation
movement of air and its replacement with fresh air due to the effects of wind, temperature
gradients, or artificial means (for example, fans or extractors)
3.17
lower explosive limit (LEL)
concentration of flammable gas, vapour or mist in air below which an explosive gas
atmosphere will not be formed
[IEV 426-02-09]
3.18
upper explosive limit (UEL)
concentration of flammable gas, vapour or mist in air, above which an explosive gas
atmosphere will not be formed
[IEV 426-02-10]
3.19
relative density of a gas or a vapour
density of a gas or a vapour relative to the density of air at the same pressure and at the
same temperature (air is equal to 1,0)
3.20
flammable material (flammable substance)
material which is flammable of itself, or is capable of producing a flammable gas, vapour or
mist
3.21
flammable liquid
liquid capable of producing a flammable vapour under any foreseeable operating conditions
NOTE An example of a foreseeable operating condition is one in which the flammable liquid is handled at
temperatures close to or above its flash point.
3.22
flammable gas or vapour
gas or vapour which, when mixed with air in certain proportions, will form an explosive gas
atmosphere
3.23
flammable mist
droplets of liquid, dispersed in air so as to form an explosive atmosphere

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3.24
flashpoint
lowest liquid temperature at which, under certain standardized conditions, a liquid gives off
vapours in a quantity such as to be capable of forming an ignitable vapour/air mixture
3.25
boiling point
temperature of a liquid boiling at an ambient pressure of 101,3 kPa (1 013 mbar)
NOTE The initial boiling point that should be used for liquid mixtures is to indicate the lowest value of the boiling
point for the range of liquids present, as determined in a standard laboratory distillation without fractionation.
3.26
vapour pressure
pressure exerted when a solid or liquid is in equilibrium with its own vapour. It is a function of
the substance and of the temperature
3.27
ignition temperature of an explosive gas atmosphere
lowest temperature of a heated surface which, under specified conditions according to
IEC 60079-4, will ignite a flammable substance in the form of a gas or vapour mixture with air
[IEC 60079-0, definition 3.26]
3.28
extent of zone
distance in any direction from the source of release to the point where the gas/air mixture has
been diluted by air to a value below the lower explosive limit
3.29
liquefied flammable gas
flammable material which is stored or handled as a liquid and which at ambient temperature
and atmospheric pressure is a flammable gas
4 General
4.1 Safety principles
Installations in which flammable materials are handled or stored should be designed,
operated and maintained so that any releases of flammable material, and consequently the
extent of hazardous areas, are kept to a minimum, whether in normal operation or otherwise,
with regard to frequency, duration and quantity.
It is important to examine those parts of process equipment and systems from which release
of flammable material may arise and to consider modifying the design to minimise the
likelihood and frequency of such releases and the quantity and rate of release of material.
These fundamental considerations should be examined at an early stage of the design
development of any process plant and should also receive prime attention in carrying out the
area classification study.
In the case of activities other than those of normal operation, e.g. commissioning or
maintenance, the area classification may not be valid. It is expected that this would be dealt
with by a safe system of work.
In a situation in which there may be an explosive gas atmosphere, the following steps should
be taken:

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60079-10-1 © IEC:2008 – 11 –
a) eliminate the likelihood of an explosive gas atmosphere occurring around the source of
ignition, or
b) eliminate the source of ignition.
Where this is not possible, protective measures, process equipment, systems and procedures
should be selected and prepared so the likelihood of the coincidence of a) and b) is so small
as to be acceptable. Such measures may be used singly, if they are recognized as being
highly reliable, or in combination to achieve the required level of safety.
4.2 Area classification objectives
Area classification is a method of analysing and classifying the environment where explosive
gas atmospheres may occur so as to facilitate the proper selection and installation of
equipment to be used safely in that environment. The classification also takes into account
the ignition characteristics of the gas or vapour such as ignition energy (gas group) and
ignition temperature (temperature class).
In most practical situations where flammable materials are used, it is difficult to ensure that an
explosive gas atmosphere will never occur. It may also be difficult to ensure that equipment
will never give rise to a source of ignition. Therefore, in situations where an explosive gas
atmosphere has a high likelihood of occurring, reliance is placed on using equipment which
has a low likelihood of creating a source of ignition. Conversely, where the likelihood of an
explosive gas atmosphere occurring is reduced, equipment constructed with less rigorous
requirements may be used.
Subsequent to the completion of the area classification, a risk assessment may be carried out
to assess whether the consequences of ignition of an explosive atmosphere requires the use
of equipment of a higher equipment protection level (EPL) or may justify the use of equipment
with a
...