EN IEC 60079-10-1:2021

SLOVENSKI STANDARD
01-april-2021
Nadomešča:
SIST EN 60079-10-1:2016
Eksplozivne atmosfere - 10-1. del: Razvrstitev prostorov - Eksplozivne plinske
atmosfere (IEC 60079-10-1:2020)
Explosive atmospheres - Part 10-1: Classification of areas - Explosive gas atmospheres
(IEC 60079-10-1:2020)
Explosionsgefährdete Bereiche - Teil 10-1: Einteilung der Bereiche -
Gasexplosionsgefährdete Bereiche (IEC 60079-10-1:2020)
Atmosphères explosives - Partie 10-1: Classement des emplacements - Atmosphères
explosives gazeuses (IEC 60079-10-1:2020)
Ta slovenski standard je istoveten z: EN IEC 60079-10-1:2021
ICS:
29.260.20 Električni aparati za Electrical apparatus for
eksplozivna ozračja explosive atmospheres
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 60079-10-1

NORME EUROPÉENNE
EUROPÄISCHE NORM
February 2021
ICS 29.260.20 Supersedes EN 60079-10-1:2015 and all of its
amendments and corrigenda (if any)
English Version
Explosive atmospheres - Part 10-1: Classification of areas -
Explosive gas atmospheres
(IEC 60079-10-1:2020)
Atmosphères explosives - Partie 10-1: Classification des Explosionsgefährdete Bereiche - Teil 10-1: Einteilung der
emplacements - Atmosphères explosives gazeuses Bereiche - Gasexplosionsgefährdete Bereiche
(IEC 60079-10-1:2020) (IEC 60079-10-1:2020)
This European Standard was approved by CENELEC on 2021-01-22. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60079-10-1:2021 E

European foreword
The text of document 31J/307/FDIS, future edition 3 of IEC 60079-10-1, prepared by SC 31J
"Classification of hazardous areas and installation requirements" of IEC/TC 31 "Equipment for
explosive atmospheres" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN IEC 60079-10-1:2021.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2021-10-22
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2024-01-22
document have to be withdrawn
This document supersedes EN 60079-10-1:2015 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Endorsement notice
The text of the International Standard IEC 60079-10-1:2020 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards
indicated:
IEC 60079-0 NOTE Harmonized as EN IEC 60079-0
IEC 60079-14 NOTE Harmonized as EN 60079-14
IEC 60079-13 NOTE Harmonized as EN 60079-13
IEC 60079-10-2 NOTE Harmonized as EN 60079-10-2
IEC 61285 NOTE Harmonized as EN 61285
IEC 61511-1:2016 NOTE Harmonized as EN 61511-1:2017 (not modified)
ISO/IEC 80079-20-1 NOTE Harmonized as EN ISO/IEC 80079-20-1

IEC 60079-10-1 ®
Edition 3.0 2020-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 10-1: Classification of areas – Explosive gas atmospheres

Atmosphères explosives –
Partie 10-1: Classification des emplacements – Atmosphères explosives

gazeuses
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-8890-0

– 2 – IEC 60079-10-1:2020 © IEC 2020
CONTENTS
FOREWORD . 6
INTRODUCTION . 10
1 Scope . 11
2 Normative references . 11
3 Terms and definitions . 12
4 General . 16
4.1 Safety principles . 16
4.2 Hazardous area classification objectives . 17
4.3 Interior of equipment containing flammable materials . 18
4.4 Explosion risk assessment . 18
4.4.1 General . 18
4.4.2 Zone of negligible extent. 18
4.5 Catastrophic failures . 19
4.6 Competence of personnel . 19
5 Hazardous area classification methodology . 19
5.1 General . 19
5.2 Classification by sources of release method . 20
5.3 Use of industry codes and national standards . 21
5.3.1 General . 21
5.3.2 Fuel gas installations . 21
5.4 Simplified methods. 21
5.5 Combination of methods . 21
6 Release of flammable substance . 22
6.1 General . 22
6.2 Sources of release . 22
6.3 Forms of release . 23
6.3.1 General . 23
6.3.2 Gaseous release . 24
6.3.3 Liquefied under pressure release . 24
6.3.4 Liquefied by refrigeration release . 24
6.3.5 Flammable mists release . 25
6.3.6 Vapours release . 25
6.3.7 Liquid release . 25
7 Ventilation (or air movement) and dilution . 26
7.1 General . 26
7.2 Main types of ventilation . 27
7.2.1 General . 27
7.2.2 Natural ventilation . 27
7.2.3 Artificial ventilation . 27
7.2.4 Degree of dilution . 29
8 Type of zone . 30
8.1 General . 30
8.2 Influence of grade of the source of release . 30
8.3 Influence of dilution . 30
8.4 Influence of availability of ventilation . 30
9 Extent of zone . 31

IEC 60079-10-1:2020 © IEC 2020 – 3 –
10 Documentation . 31
10.1 General . 31
10.2 Drawings, data sheets and tables . 32
Annex A (informative) Suggested presentation of hazardous areas . 33
A.1 Hazardous area – Preferred symbols for zones . 33
A.2 Hazardous area suggested shapes . 36
Annex B (informative) Estimation of sources of release . 38
B.1 Symbols . 38
B.2 Examples of grade of release . 38
B.2.1 General . 38
B.2.2 Sources giving a continuous grade of release . 39
B.2.3 Sources giving a primary grade of release . 39
B.2.4 Sources giving a secondary grade of release . 39
B.3 Assessment of grades of release . 39
B.4 Summation of releases . 40
B.5 Hole size and source radius . 41
B.6 Forms of release . 43
B.7 Release rate . 44
B.7.1 General . 44
B.7.2 Estimation of release rate . 45
B.7.3 Release rate of evaporative pools . 47
B.8 Release from openings in buildings . 49
B.8.1 General . 49
B.8.2 Openings as possible sources of release . 50
B.8.3 Openings classification . 50
Annex C (informative) Ventilation guidance . 52
C.1 Symbols . 52
C.2 General . 53
C.3 Assessment of ventilation and dilution and its influence on hazardous area . 53
C.3.1 General . 53
C.3.2 Effectiveness of ventilation . 54
C.3.3 Criteria for dilution . 54
C.3.4 Assessment of ventilation velocity . 55
C.3.5 Assessment of the degree of dilution . 56
C.3.6 Dilution in a room . 58
C.3.7 Criteria for availability of ventilation . 59
C.4 Examples of ventilation arrangements and assessments . 60
C.4.1 Introduction . 60
C.4.2 Jet release in a large building . 61
C.4.3 Jet release in a small naturally ventilated building . 62
C.4.4 Jet release in a small artificially ventilated building . 62
C.4.5 Release with low velocity . 63
C.4.6 Fugitive emissions . 63
C.4.7 Local ventilation-extraction . 64
C.5 Natural Ventilation in buildings . 64
C.5.1 General . 64
C.5.2 Wind induced ventilation . 64
C.5.3 Buoyancy induced ventilation . 65

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C.5.4 Combination of the natural ventilation induced by wind and buoyancy . 67
Annex D (informative) Estimation of hazardous areas . 69
D.1 General . 69
D.2 Estimating types of the zones . 69
D.3 Estimating the extent of the hazardous area . 70
Annex E (informative) Examples of hazardous area classification . 72
E.1 General . 72
E.2 Examples . 72
E.3 Example case study for hazardous area classification . 86
Annex F (informative) Schematic approach to classification of hazardous areas . 96
F.1 Schematic approach to classification of hazardous areas . 96
F.2 Schematic approach to classification of hazardous areas . 97
F.3 Schematic approach to classification of hazardous areas . 98
F.4 Schematic approach to classification of hazardous areas . 99
Annex G (informative) Flammable mists . 100
Annex H (informative) Hydrogen . 103
Annex I (informative) Hybrid mixtures . 105
I.1 General . 105
I.2 Use of ventilation . 105
I.3 Concentration limits . 105
I.4 Chemical reactions . 105
I.5 Energy/temperature limits . 105
I.6 Zoning requirements . 105
Annex J (informative) Useful equations in support to hazardous area classification . 106
J.1 General . 106
J.2 Dilution with air of a flammable substance release . 106
J.3 Estimate of the time required to dilute a flammable substance release . 106
Annex K (informative) Industry codes and national standards . 108
K.1 General . 108
Bibliography . 112

Figure 1 – Dilution Volume . 29
Figure A.1 – Preferred symbols for zones . 33
Figure A.2 – Gas or vapour at low pressure (or at high pressure in case of
unpredictable release direction) . 36
Figure A.3 – Gas or vapour at high pressure . 36
Figure A.4 – Liquefied gas . 37
Figure A.5 – Flammable liquid (non boiling evaporative pool) . 37
Figure B.1 – Forms of release . 43
Figure B.2 – Specific volumetric evaporation rate of liquids . 49
Figure C.1 – Chart for assessing the degree of dilution . 57
Figure C.2 – Self diffusion of an unimpeded high velocity jet release . 61
Figure C.3 – Supply only ventilation . 62
Figure C.4 – Supply and extraction ventilation . 63
Figure C.5 – Local extraction ventilation . 64
Figure C.6 – Specific volumetric flow rate of fresh air of equivalent effective opening area . 67

IEC 60079-10-1:2020 © IEC 2020 – 5 –
Figure C.7 – Example of opposing ventilation driving forces. 68
Figure D.1 – Chart for estimating hazardous area distances . 71
Figure E.1 – Degree of dilution (Example No. 1) . 73
Figure E.2 – Hazardous distance (Example No. 1) . 74
Figure E.3 – Zone classification (Example No. 1) . 74
Figure E.4 – Degree of dilution (Example No. 2) . 76
Figure E.5 – Degree of dilution (Example No. 3) . 78
Figure E.6 – Hazardous distance (Example No. 3) . 79
Figure E.7 – Zones classification (Example No. 3) . 79
Figure E.8 – Degree of dilution (Example No. 4) . 81
Figure E.9 – Hazardous distance (Example No. 4) . 82
Figure E.10 – Zones classification (Example No. 4) . 83
Figure E.11 – Degree of dilution (Example No. 5) . 85
Figure E.12 – Hazardous distance (Example No. 5) . 86
Figure E.13 – Enclosed compressor handling natural gas . 88
Figure E.14 – Example of hazardous area classification for a compressor facility
handling natural gas (elevation) . 94
Figure E.15 – Example of hazardous area classification for a compressor facility
handling natural gas (plan) . 95
Figure F.1 – Schematic approach to classification. 96
Figure F.2 – Schematic approach to classification for continuous grade releases . 97
Figure F.3 – Schematic approach to classification for primary grade releases . 98
Figure F.4 – Schematic approach to classification for secondary grade releases . 99

Table A.1 – Hazardous area classification data sheet – Part I: Flammable substance
list and characteristics . 34
Table A.2 – Hazardous area classification data sheet – Part II: List of sources of
release . 35
Table B.1 – Suggested hole cross sections for secondary grade of releases . 42
Table B.2 – Effect of zones on openings as possible sources of release . 51
Table C.1 – Indicative outdoor ventilation velocities (u ) . 56
w
Table D.1 – Zones for grade of release and effectiveness of ventilation . 69
Table E.1 – Compressor facility handling natural gas . 88
Table E.2 – Hazardous area classification data sheet – Part I: Flammable substance
list and characteristics . 91
Table E.3 – Hazardous area classification data sheet – Part II: List of sources of
release . 92
Table K.1 – Examples of codes and standards . 109

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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,
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) 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 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 third edition of IEC 60079-10-1 cancels and replaces the second edition, published in
2015, and constitutes a technical revision. The significant technical changes with respect to
the previous edition are as follows:

IEC 60079-10-1:2020 © IEC 2020 – 7 –
Type
Minor and Major
Changes Clause editorial Extension technical
changes changes
Deleting commercial and industrial applications for
1  C1
fuel gas from the Scope exemptions
Updating editorial details and notes to the definitions 3 X
Deletion of the previous edition clause 3.7.3
definition for catastrophic failure (dealt with in clause X
4.5)
Introduction of new Subclause 4.4.2 Zone of
4.4.2 X
negligible extent
Introduction of new clause 5.3.2 Fuel gas
5.3.2 X
installations
Renumbering of headings 7 X
Introduction of Figure 1 – Dilution volume 7 X
Upgrading Table A.1 with UFL and its column 15
A.1 X
heading with the ‘source of data’
Updating the flow-chart in Figure B.1 B.6 X
Updating equations for evaporation rate to align with
B.7.3 X
the recent source modifications
Updating the chart in Figure B.2 according to the
updated equations for evaporation rate and the B.7.3 X
ventilation velocity of 0,25 m/s
Restructuring Table C.1 C.3.4 X
Removal of safety factor k and deleting it from the
C.3.5 C2
horizontal axis of the chart in Figure C.1
Revising equations (C.2) and (C.3) C.5.2  C3
Revising equations (C.4) and (C.5) C.5.3  C4
Revising the chart in Figure C.6 by changing the
C.5.3 C5
label on the horizontal axis
Revising equation (C.6) and deleting equation (C.7) C.5.4  C6
Removal of safety factor k and deleting it from the
D.3 C7
horizontal axis of the charts in Figure D.1
Imposing limitations to the use of the chart in Figure
D.3 X
D.1
Updating and corrections in Annex E Annex E X
Upgrading Annex G on Flammable mists Annex G X
Introducing new items in Table K.1 Annex K X
Introducing new items in the Bibliography Bibliography X
NOTE The technical changes referred to include the significance of technical changes in the revised IEC
Standard, but they do not form an exhaustive list of all modifications from the previous version.

– 8 – IEC 60079-10-1:2020 © IEC 2020
Explanations:
A) Definitions
Minor and editorial changes clarification
decrease of technical requirements
minor technical change
editorial corrections
These are changes which modify requirements in an editorial or a minor technical way. They
include changes of the wording to clarify technical requirements without any technical change.
Extension addition of technical options
These are changes which add new or modify existing technical requirements, in a way that
new options are given, but without increasing requirements.
Major technical changes addition of technical requirements
increase of technical requirements
B) Information about the background of changes
C1  The previous edition item e) was: “commercial and industrial applications where only low
pressure fuel gas is used for appliances e.g. for cooking, water heating and similar
uses, where the installation is compliant with relevant gas codes”. Industrial
applications of any kind should not be exempted from the scope of this standard. See
also new clause 5.3.2.
C2   The factor k was initially intended to provide for additional safety for uncertainties in
determining LFL for flammable substances, particularly gas mixtures. However, this
was considered as unnecessary and confusing considering the derivation of the chart.
C3    The equations are updated to align with BS 5925
C4    The equations are updated to align with BS 5925
C5    The chart is revised to match the new equation (C.4)
C6    The equation is updated to align with BS 5925
C7    See the explanation under C2
These are changes to technical requirements (addition, increase of the level or removal).
NOTE These changes represent current technological knowledge. However, these changes should not normally
have an influence on equipment already placed on the market.
The text of this standard is based on the following documents:
FDIS Report on voting
31J/307/FDIS 31J/310/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document 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.
IEC 60079-10-1:2020 © IEC 2020 – 9 –
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 10 – IEC 60079-10-1:2020 © IEC 2020
INTRODUCTION
In areas where dangerous quantities and concentrations of flammable gas or vapour may
arise, measures need 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 hazards.
IEC 60079-10-1:2020 © IEC 2020 – 11 –
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 hazards may arise and may then be used as a basis to support the proper design,
construction, operation and maintenance of equipment for use in hazardous areas.
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, but it does not apply to:
a) mines susceptible to firedamp;
b) the processing and manufacture of explosives;
c) catastrophic failures or rare malfunctions which are beyond the concept of normality dealt
with in this standard (see 3.7.3 and 4.5);
d) rooms used for medical purposes;
e) domestic premises;
f) where a hazard may arise due to the presence of combustible dusts or combustible flyings
but the principles may be used in assessment of a hybrid mixture (refer also to
IEC 60079-10-2).
NOTE Additional guidance on hybrid mixtures is provided in Annex I.
Flammable mists may form or be present at the same time as flammable vapour. In such case
the strict application of the details in this document may not be appropriate. Flammable mists
may also form when liquids not considered to be a hazard due to the high flash point are
released under pressure. In these cases the classifications and details given in this document
do not apply. Information on flammable mists is provided in Annex G.
For the purpose of this document, an area is a three-dimensional region or space.
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 substances.
In any site, 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 is applicable with judgement for other ignition sources but in some
applications other safeguards may also need to be considered. E.g. larger distances may
apply for naked flames when considering hot work permits.
This document does not take into account the consequences of ignition of an explosive
atmosphere except where a zone is so small that if ignition did occur it would have negligible
consequences (see 3.3.8 and 4.4.2).
2 Normative references
This document contains no normative references.

– 12 – IEC 60079-10-1:2020 © IEC 2020
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60079-0 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
NOTE Additional definitions applicable to explosive atmospheres can be found in IEC 60050-426.
3.1
explosive atmosphere
mixture with air, under atmospheric conditions, of flammable substances in the form of gas,
vapour, or dust which, after ignition, permits self-sustaining propagation
[SOURCE: IEC 60079-0:2017, 3.38]
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
Note 1 to entry: Although a mixture which has a concentration above the upper flammable limit (UFL) is not an
explosive gas atmosphere, it can readily become so and, generally for hazardous area classification purposes, it is
advisable to consider it as an explosive gas atmosphere.
Note 2 to entry: There are some gases and vapours which are explosive with the concentration of 100 % (e.g.
acetylene, CAS no. 74-86-2, C H ; monovinyl acetylene, CAS no. 689-97-4, C H ; 1-propyl nitrate (vapour), CAS
2 2 4 4
no. 627-13-4, CH (CH ) NO ; isopropyl nitrate (vapour), CAS no. 1712-64-7, (CH ) CH ONO ; ethylene oxide
3 2 2 3 3 2 2
(vapour), CAS no. 75-21-8, (CH ) O; hydrazine (vapour), CAS no. 302-01-2, H N .
2 2 4 2
[SOURCE: IEC 60079-0:2017, 3.40, modified (addition of Notes to entry)]
3.3
hazardous areas and zones
3.3.1
hazardous area
area in which an explosive gas atmosphere is present or can be expected to be present, in
quantities such that special precautions for the construction, installation and use of equipment
are required
3.3.2
non-hazardous area
area in which an explosive gas atmosphere is not expected to be present in quantities such
that special precautions for the construction, installation and use of equipment are required
3.3.3
zone
hazardous area classification based on the frequency of the occurrence and duration of the
explosive atmosphere
3.3.4
Zone 0
area in which an explosive gas atmosphere is present continuously, or for long periods, or
frequently
IEC 60079-10-1:2020 © IEC 2020 – 13 –
Note 1 to entry: Both “long” and “frequently” are the terms which are intended to describe a very high likelihood of
a potentially explosive atmosphere in the area. In that respect, those terms do not necessarily need to be
quantified.
3.3.5
Zone 1
area in which an explosive gas atmosphere is likely to occur occasionally in normal operation
3.3.6
Zone 2
area in which an explosive gas atmosphere is not likely to occur in normal operation, but, if it
does occur, will exist for a short period only
Note 1 to entry: Indications of the frequency of the occurrence and duration of the explosive atmosphere can be
taken from codes or standards relating to specific industries or applications.
[SOURCE: IEC 60050-426:2020, 426-03-05]
3.3.7
extent of zone
distance in any direction from the source of release to where a gas/air mixture will be diluted
by air to a concentration below the lower flammable limit
3.3.8
Zone NE
zone of negligible extent such that if ignition did occur it would have negligible consequences
Note 1 to entry: Zones of negligible extent could be Zone 0 NE, Zone 1 NE or Zone 2 NE.
3.4
releases
3.4.1
source of release
point or location from which a flammable gas, vapour, mist or liquid may be released into the
atmosphere so that an explosive gas atmosphere could be formed
[SOURCE: IEC 60050-426:2020, 426-03-06]
3.4.2
continuous grade of release
release which is continuous or is expected to occur frequently or for long periods
Note 1 to entry: Both “frequently” and “long” are the terms which are intended to describe a very high likelihood of
a potential release. In that respect, those terms do not necessarily need to be quantified.
3.4.3
primary grade of release
release which can be expected to occur periodically or occasionally during normal operation
3.4.4
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
3.4.5
release rate
quantity of flammable gas, liquid, vapour or mist emitted per unit time from the source of
release
– 14 – IEC 60079-10-1:2020 © IEC 2020
3.5
ventilation and dilution
3.5.1
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)
Note 1 to entry: Fresh air is intended to be synomonous with the term ‘clean air’ used in IEC 60079-13. Both terms
mean air that is essentially free of flammable gas or vapour.
3.5.2
dilution
mixing of flammable vapour or gas with air which, over time, will reduce the flammable
concentration
3.5.3
dilution volume
volume in the vicini
...