IEC 60079-2:2014

IEC 60079-2 ®
Edition 6.0 2014-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 2: Equipment protection by pressurized enclosure "p"

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IEC 60079-2 ®
Edition 6.0 2014-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 2: Equipment protection by pressurized enclosure "p"

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.260.20 ISBN 978-2-8322-1775-7

– 2 – IEC 60079-2:2014 RLV © 2014
CONTENTS
FOREWORD . 7
INTRODUCTION . 16
1 Scope . 17
2 Normative references . 17
3 Terms and definitions . 18
4 Protection types levels . 21
5 Constructional requirements for pressurized enclosures . 24
5.1 Enclosure . 24
5.2 Materials . 24
5.3 Doors and covers . 24
5.3.1 Group I pressurized enclosures . 24
5.3.2 Group I pressurized enclosures with static pressurization . 24
5.3.3 Group II and Group III pressurized enclosures . 24
5.3.4 Group II and Group III pressurized enclosures with static pressurization . 25
5.3.5 Type px Group II and Group III Level of Protection “pxb” . 25
5.3.6 Marking for Group I or Group II and Group III Door and Cover warning . 25
5.4 Mechanical strength . 25
5.5 Group I and Group II Apertures, partitions, compartments and internal
components . 25
5.6 Apertures for Static Pressurization . 26
5.7 Insulating materials for Group I equipment . 26
5.8 Sealing . 26
5.9 Spark and particle barriers . 26
5.10 Cells and batteries . 25
6 Temperature limits . 27
6.1 General . 27
6.2 For type px or type py Level of Protection “pxb” or Level of Protection “pyb” . 27
6.3 For type pz Level of Protection “pzc” . 28
7 Safety provisions and safety devices (except for static pressurization) . 28
7.1 Suitability of safety devices for hazardous area . 28
7.2 Integrity of safety devices . 28
7.3 Provider of safety devices . 29
7.4 Pressurization System evaluated as associated equipment . 29
7.4.1 Pressurization systems for Level of Protection ”pzc”. . 29
7.4.2 Pressurization systems for Level of Protection ”pyb”. . 29
7.4.3 Pressurization systems for Level of Protection ”pxb”. . 29
7.5 Sequence diagram for type px Level of Protection “pxb” . 30
7.6 Ratings for safety devices . 30
7.7 Group I and Group II – Purging automated for type px Level of Protection
“pxb” . 30
7.8 Group I or Group II − Purging criteria . 30
7.9 Group III – Cleaning . 31
7.10 Requirements when a minimum flow rate required . 31
7.11 Safety devices to detect minimum overpressure . 31
7.12 Value of minimum overpressure . 32
7.13 Pressurizing multiple enclosures . 32

7.14 Safety devices on doors and covers . 33
7.15 Protection types Equipment that may remain energized . 33
7.16 Protection types Equipment permitted within type py Level of Protection
“pyb” . 33
8 Safety provisions and safety devices for static pressurization . 33
8.1 Suitability of safety devices for hazardous area . 33
8.2 Protective gas . 34
8.3 Internal sources of release . 34
8.4 Group I and Group II – Filling procedure . 34
8.5 Group III – Filling Procedure . 34
8.6 Safety devices . 34
8.7 Protection types Equipment that may remain energized . 34
8.8 Overpressure . 34
9 Supply of protective gas . 34
9.1 Backup supply . 34
9.2 Independent supplies . 35
9.3 Type of gas . 35
9.4 Temperature . 35
10 Pressurized equipment with an internal source of release . 35
11 Release conditions . 35
11.1 No release . 35
11.2 Limited release of a gas or vapour . 36
11.3 Limited release of a liquid . 36
12 Design requirements for the containment system . 36
12.1 General design requirements . 36
12.2 Infallible containment system . 37
12.3 Containment system with a limited release . 37
13 Protective gas and pressurizing techniques when there is an internal source of
release . 38
13.1 General . 38
13.2 Pressurization with leakage compensation . 38
13.2.1 No release . 38
13.2.2 Limited release of a gas or liquid . 38
13.3 Pressurization with dilution . 39
13.3.1 General . 39
13.3.2 No release . 39
13.3.3 Limited release of a gas or vapour . 39
13.3.4 Limited release of a liquid . 39
14 Ignition-capable apparatus equipment . 39
15 Internal hot surfaces . 40
16 Type verification and tests . 40
16.1 Determining the maximum overpressure rating . 40
16.2 Maximum overpressure test . 40
16.3 Leakage test . 41
16.3.1 Other than static pressurization . 41
16.3.2 Static pressurization . 41

– 4 – IEC 60079-2:2014 RLV © 2014
16.4 Purging test for pressurized enclosures with no internal source of
release(pressurization technique may be leakage compensation or
continuous flow) and filling procedure test for static pressurization . 41
16.4.1 General . 41
16.4.2 Pressurized enclosure where the protective gas is air . 41
16.4.3 Pressurized enclosure where the protective gas is inert . 41
16.4.4 Pressurized enclosure where the protective gas may be either air or an
inert gas with a density equal to air ±10 % . 42
16.4.5 Filling procedure test for a pressurized enclosure protected by static
pressurization . 42
16.5 Purging and dilution tests for a pressurized enclosure with an internal source
of release . 42
16.5.1 Test gas . 42
16.5.2 Pressurized enclosure where the flammable substance has less than
2 % (V/V) oxygen and the protective gas is inert . 42
16.5.3 Pressurized enclosure with pressurization by continuous flow,
containment system with less than 21 % (V/V) oxygen and the
protective gas is inert . 42
16.5.4 Pressurized enclosure where the flammable substance is not a liquid,
pressurization by continuous flow and the protective gas is air . 43
16.6 Verification of minimum overpressure . 44
16.7 Tests for an infallible containment system . 44
16.7.1 Overpressure test . 44
16.7.2 Infallibility test . 44
16.8 Overpressure test for a containment system with a limited release . 45
17 Routine tests . 45
17.1 Functional test . 45
17.2 Leakage test . 45
17.3 Tests for an infallible containment system . 45
17.4 Test for a containment system with a limited release . 45
18 Marking . 46
18.1 Warnings General . 46
18.2 Identifying as pressurized . 46
18.3 Supplementary marking . 46
18.4 Internal source of release . 46
18.5 Static pressurization . 47
18.6 Pressurization systems . 47
18.7 Warnings required in other clauses . 47
18.8 Overpressure limited by user . 48
18.9 Inert gas . 48
19 Instructions . 48

Annex A (normative) Purging and dilution tests . 49
A.1 Geneal . 49
A.2 Criteria for compliance where the protective gas is inert . 49
A.3 Criteria for compliance where the protective gas is inert . 49
Annex B (informative) Examples of functional sequence diagram . 50
Annex C (informative) Examples of the changes in pressure in ducts and enclosures . 52
Annex D (informative) Information to be provided to the user . 57
D.1 General . 57

D.2 Ducting of protective gas . 57
D.2.1 Location of inlet . 57
D.2.2 Ducting between pressurized enclosure and inlet . 57
D.2.3 Outlets for protective gas . 57
D.2.4 Additional purge time to account for ducting . 58
D.2.5 Temperature of protective gas at the inlet . 58
D.3 Power for protective gas supply . 58
D.4 Static pressurization . 58
D.5 Enclosures with a containment system . 58
D.6 Enclosure maximum overpressure . 58
Annex E (normative) Classification of the type of release within enclosures . 59
E.1 General . 59
E.2 No normal release, no abnormal release . 59
E.3 No normal release, limited abnormal release. 59
E.4 Limited normal release . 59
Annex F (informative) Examples for the use of the dilution area concept . 60
Annex G (normative) Infallibility test for containment system . 60
Annex G (normative) Internal Cells and Batteries for Level of Protection “pxb” and
Level of Protection “pyb” . 67
G.1 General Requirements . 67
G.1.1 General . 67
G.1.2 Accepted Electrochemical Systems . 67
G.1.3 Secondary cells and secondary batteries . 67
G.1.4 Mechanical Protection . 67
G.2 Electrical Protection by energy limiting circuits. . 68
G.2.1 Assessing as energy limited . 68
G.2.2 Protective Components . 68
G.2.3 Preventing excessive gas pressure . 68
G.3 Additional requirements for Primary batteries . 69
G.3.1 Prevention of reverse charging. . 69
G.3.2 Prevention of accidental charging of primary batteries . 69
G.4 Additional requirements for secondary batteries . 70
G.4.1 Charging of secondary batteries inside the pressurized housing . 70
G.5 Specific requirements for Inherently Safe (IhS) cells and batteries . 70
G.6 Equipment located inside a pressurized enclosure connected to a battery
which is also located inside the pressurized enclosure and not disconnected
in the event of loss of pressurization . 71
G.6.1 General . 71
G.6.2 Circuit Isolation . 71
G.6.3 Intrinsically safe battery or inherently safe battery used with “Ex”
equipment. 71
G.6.4 Intrinsically Safe or Inherently Safe battery with non-"Ex" equipment. . 71
G.7 Supplementary marking and constructional requirements for pressurized
enclosures containing one or more cells or batteries . 73
G.7.1 General . 73
G.7.2 Battery removal warning . 73
G.7.3 Batteries requiring routine maintenance . 73
G.8 Type tests . 73
G.8.1 Voltage . 73

– 6 – IEC 60079-2:2014 RLV © 2014
G.8.2 Short circuit test for an Inherently Safe Cell or Battery . 73
G.8.3 Full load test for other than Inherently safe batteries . 73
Annex H (informative) Introduction of an alternative risk assessment method
encompassing “equipment protection levels” for Ex equipment . 61
Annex H (normative) Internal Cells and Batteries for Level of Protection “pzc” . 74
H.1 General Requirements . 74
H.1.1 General . 74
H.1.2 Accepted Electrochemical Systems . 74
H.1.3 Secondary cells and secondary batteries . 74
H.1.4 Mechanical Protection . 74
H.2 Equipment located inside a pressurized enclosure connected to a battery
which is also located inside the pressurized enclosure and is not
disconnected when power is removed from the enclosure. . 75
H.3 Supplementary marking and constructional requirements for pressurized
enclosures containing one or more cells or batteries . 75
H.3.1 General . 75
H.3.2 Battery removal warning . 75
H.3.3 Batteries requiring routine maintenance . 75

Bibliography . 76

Figure B.1 – State diagram of a leakage-compensation purge control system . 50
Figure C.1 – Protective gas outlet . 53
Figure C.2 – Pressurized enclosures with leakage compensation, enclosures without
moving parts . 54
Figure C.3 – Pressurized enclosures with leakage compensation, rotating electrical
machine with an internal cooling fan . 55
Figure C.4 – Pressurized enclosure with a leakage compensation, rotating electrical
machine with an external cooling fan . 56
Figure F.1 – Diagram showing the use of the dilution area concept to simplify the purge
and dilution test requirements . 60
Figure F.2 – Diagram showing the use of the infallible containment system concept to
simplify the purging and dilution requirements around ICAE . 61
Figure F.3 – Diagram showing the use of internal partitions around the potential source
of release to simplify the purging and dilution requirements around ICAE located
outside the partitions . 61
Figure G.1 – Reverse charging protection . 69
Figure G.2 – Accidental charging protection . 69

Table 1 – Determination of protection type level . 22
Table 2 – Design criteria based upon type level of protection . 23
Table 3 – Safety devices based upon protection type Level of Protection . 28
Table 4 – Protective gas requirements for a pressurized enclosure with a containment
system . 38
Table 5 – Equipment Protection types Levels permitted within the dilution
area based upon the Level of Protection of the pressurized enclosure . 39
Table 6 – Text of warning markings . 47
Table B.1 – Truth table of a leakage-compensation purge control system . 50

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 2: Equipment protection by pressurized enclosure "p"

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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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.
This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.

– 8 – IEC 60079-2:2014 RLV © 2014
International Standard IEC 60079-2 has been prepared by technical committee 31: Explosive
atmospheres.
This sixth edition cancels and replaces the fifth edition published in 2007. This sixth edition
cancels and replaces the first edition of IEC 61241-4 published in 2001. This sixth edition
constitutes a technical revision.
The significance of changes between IEC 60079-2, Edition 6.0, 2014 and IEC 60079-2,
Edition 5.0, 2007 are as listed below:
Type
Changes Clause Minor and Extension Major
Editorial Technical
Changes Changes
Scope 1 X
Expanded to include combustible dust
Protective Gas 3
Replaced “apparatus” with “equipment”
Protective Gas 3.16 X
Revised to show that purging is not required for explosive dust
atmospheres
Level of Protection “pxb” 3.21 X
Term and definitions revised to reflect EPL and level of
protection
Level of Protection “pyb” 3.22 X
Term and definitions revised to reflect EPL and level of
protection
Level of Protection “pzc” 3.23 X
Term and definitions revised to reflect EPL and level of
protection
Lower Flammable Limit 3.26 X
Term and definition revised to agree with 60079-0
Upper Flammable Limit 3.27 X
Term and definition revised to agree with 60079-0
Table 1 – Determination of protection level Table 1 X
Revised to use EPL terminology
Table 2 – Design Criteria based upon level of protection Table 2 X
Revised to use EPL terminology
Enclosure 5.1 X
Requirements relaxed for specific designs
Group II and Group III pressurized enclosures 5.3.3 X
Text revised to use EPL terminology
Group II and Group III Level of Protection “pxb” 5.3.5 X
Added that warning also applies for explosive dust atmospheres
Group II and Group III door and cover warning 5.3.6 X
Added that warning also applies for explosive dust atmospheres
Group II and Group III door and cover warning 5.3.6 X
Revised warning from atmosphere “may be present” to “is
present”
Type
Changes Clause Minor and Extension Major
Editorial Technical
Changes Changes
Mechanical Strength 5.4 X
Removed reference to 60079-0 by clause number for “X”
condition
Spark and particle barriers 5.9 X
Removed reference to 60079-0 by clause number for “X”
condition
Cells and batteries 5.10  C1
Added requirements for cells and batteries
For Level of Protection “pxb” or Level of Protection “pyb” 6.2 X
Revised Table to use terminology consistent with EPLs
Suitability of safety devices for hazardous area 7.1 X
Word “explosion” changed to “ignition” to reflect UFL/LFL terms
Integrity of safety devices 7.2  C2
Added requirement for detecting fan failure
Table 3 – Safety devices based upon Level of Protection Table 3 X
Revised column labels to use Level of Protection terminology
Provider of safety devices 7.3 X
Remove reference to 60079-0 by clause number for “X” condition
Pressurization System evaluated as associated equipment 7.4  C3
Added requirements for pressurization systems
Sequence diagram for Level of Protection “pxb” 7.5 X
Revised text to use Level of Protection terminology
Group I and Group II purging automated for Level of Protection 7.7 X
“pxb”
Revised text to use Level of Protection terminology
Group I and Group II purging automated for Level of Protection 7.7  C4
“pxb”
Added text specifying that for “pxb”, control must be automated
Group I or Group II – purging criteria 7.8 X
Revised text to use Level of Protection terminology
Group III – cleaning 7.9 X
Added text for cleaning enclosures used in explosive dust
atmospheres
Safety devices to detect minimum overpressure 7.11 X
Add word “minimum” to clause title to be consistent with text
Safety devices to detect minimum overpressure 7.11 d) X
Revised text to use Level of Protection terminology
Value of minimum overpressure 7.12 X
Added word “minimum” to clause title to be consistent with text
Value of minimum overpressure 7.12 X
Revised text to use Level of Protection terminology
Value of minimum overpressure 7.12 X
Added text to reflect a note in Annex C
Pressurizing multiple enclosures 7.13 X
Revised text to use Level of Protection terminology

– 10 – IEC 60079-2:2014 RLV © 2014
Type
Changes Clause Minor and Extension Major
Editorial Technical
Changes Changes
Safety devices on doors and covers 7.14 X
Revised text to use Level of Protection terminology
Equipment that may remain energized 7.15 X
Revised text to use EPL and level of protection terminology
Equipment permitted within Level of Protection “pyb” 7.16 X
Revised text to use EPL and level of protection terminology
Group I and Group II Filling procedure 8.4 X
Allow filling in a hazardous location if tested as non-hazardous
Group III Filling Procedure 8.5 X
Added static pressurization filling procedure for combustible dust
Safety devices 8.6 X
Revised text to use Level of Protection terminology
Equipment that may remain energized 8.7 X
Revised text to use EPL terminology
Overpressure 8.8 X
Removed reference to 60079-0 by clause number
Backup supply 9.1  C5
Added requirements for a backup supply of protective gas
Independent supplies 9.2 X C6
Provided requirements for independence of pressurization
Release Conditions 11.1.2 X
Removed reference to 60079-0 by clause number for “X”
condition
Containment system with a limited release 12.3 X
Removed reference to 60079-0 by clause number for “X”
condition
13.3.3 Limited release of a gas or vapour 13.3.3 X
Revised text to reflect UFL/LFL terms
Ignition-capable equipment 14 X
Revised text to use Level of Protection terminology
Type verification and tests 16 X
Edition 5 clauses 16.1 to 16.7 moved to Edition 6 clauses 16.2 to
16.8
Determining the maximum overpressure rating 16.1  C7
Added requirements to determine maximum overpressure
Maximum overpressure test 16.2  C7
Moved Maximum overpressure test to 16.2
Leakage test 16.3.2 X
Clarify the acceptance criteria for the test
Tests for an infallible containment system 16.7.1  C8
Clarify the rating used for the test
Tests for an infallible containment system 16.7.2  C9
Modified test for infallible containment

Type
Changes Clause Minor and Extension Major
Editorial Technical
Changes Changes
16.8  C7
Edition 5 − Verifying ability of the pressurized enclosure to limit
internal pressure
Eliminated test
Functional test 17.1 X
Clarified that applies only to safety devices provided with
enclosures
Tests for an infallible containment system 17.3 X
Waived helium leak tests for liquid systems
Supplementary marking 18.3
Allowed continued use of type of protection marking
Pressurization systems 18.6 X
Clarified use of Ex [p] and [Ex p] marking
Warnings required in other clauses 18.7 X
Added table number
Warnings required in other clauses 18.7 X
Added warning from 7.9
Warnings required in other clauses 18.7  C1
Added warnings from Annex G and Annex H
Instructions 19 X
Added requirements for Group III
Edition 5 Annex G – Infallibility test for containment system Annex G X
Deleted and replaced
Edition 5 Annex H – Introduction of an alternative risk Annex H X
assessment method encompassing “equipment protection levels”
Deleted and replaced
Annex G – Internal Cells and Batteries for Level of Protection  X
“pxb” and Level of Protection “pyb”
Added requirements for cells and Batteries
Annex H – Internal Cells and Batteries for Level of Protection  X
“pzc”
Added requirements for cells and Batteries

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, or a reduction in level of existing requirement.
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 for equipment that was fully
compliant with the previous standard. Therefore, these will not have to be considered for
products in conformity with the preceding edition. 5.

– 12 – IEC 60079-2:2014 RLV © 2014
Major technical changes addition of technical requirements increase of technical
requirements
These are changes to technical requirements (addition, increase of the level or removal)
made in a way that a product in conformity with the preceding edition will not always be
able to fulfill the requirements given in the later edition. These changes have to be
considered for products in conformity with the preceding edition. For these changes
additional information is provided in clause B) below
B) Information about the background of ‘Major Technical Changes’
C1 – Added annexes with requirements for using cells and batteries.
C2 – Added requirement that fan failure cannot be based upon loss of power to the fan.
C3 – Added requirements for equipment evaluated as a pressurization system to provide
uniformity in the testing of such equipment.
C4 – Although, in Edition 5, the title of clause 7.6 stated automated purging, the word
automated was not in the requirement. It is intended that all “pxb” equipment have
an automated purging system to prevent energizing of ignition capable circuits until
the purge cycle has been properly completed. This requires verifying that the flow is
at least the minimum required for the purge time as well as verifying that the
minimum overpressure exists within the enclosure.
C5 – If a backup supply of protective gas is provided, then both the primary and the
backup supply needs to be capable of maintaining the required pressurization.
C6 – If a pressurized enclosure is used within a larger pressurized enclosure the
protective gas supplies need to be independent.
C7 – The previous text in 16.1 of Edition 5, assumed that the enclosures had a maximum
overpressure rating, but this is rarely the case. Some test houses relied upon the
test in 16.8 to determine the maximum overpressure. Various methods were used to
simulate regulator failure such as removing the regulator, but this also removed the
orifices that would limit the flow. Based upon test house experience, the danger of
flying fragments from the enclosure is acceptably small as either the enclosure or
the gaskets will deform to rel
...