EN 60079-2:2007

SLOVENSKI STANDARD
01-marec-2008
1DGRPHãþD
SIST EN 60079-2:2005
(NVSOR]LYQHDWPRVIHUHGHO=DãþLWDRSUHPH]QDGWODNRPS,(&
Explosive atmospheres - Part 2: Equipment protection by pressurized enclosure "p"
Explosionsfähige Atmosphäre - Teil 2: Geräteschutz durch Überdruckkapselung "p"
Atmospheres explosives - Partie 2: Protection du matériel par enveloppe a surpression
interne "p"
Ta slovenski standard je istoveten z: EN 60079-2:2007
ICS:
29.260.20 (OHNWULþQLDSDUDWL]D Electrical apparatus for
HNVSOR]LYQDR]UDþMD explosive atmospheres
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 60079-2
NORME EUROPÉENNE
November 2007
EUROPÄISCHE NORM
ICS 29.260.20 Supersedes EN 60079-2:2004

English version
Explosive atmospheres -
Part 2: Equipment protection by pressurized enclosure "p"
(IEC 60079-2:2007)
Atmosphères explosives -  Explosionsfähige Atmosphäre -
Partie 2: Protection du matériel Teil 2: Geräteschutz
par enveloppe à surpression interne "p" durch Überdruckkapselung "p"
(CEI 60079-2:2007) (IEC 60079-2:2007)

This European Standard was approved by CENELEC on 2007-11-01. 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 Central Secretariat 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 Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2007 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60079-2:2007 E
Foreword
The text of document 31/668/FDIS, future edition 5 of IEC 60079-2, prepared by IEC TC 31, Equipment
for explosive atmospheres, was submitted to the IEC-CENELEC parallel vote and was approved by
CENELEC as EN 60079-2 on 2007-11-01.
This European Standard supersedes EN 60079-2:2004 + corrigendum April 2006.
The significant changes with respect to EN 60079-2:2004 are listed below:
– introduction of the “Equipment protection level concept” – See Annex H;
– 3.13 eliminate reference to “room” in the definition of pressurization;
– 5.3.3 restrict to type px;
– 5.3.3 add warning for type pz and type py for any cover removable without the use of a tool;
– 7.6 move wording “For type px” to beginning of subclause to clarify 7.6 only applies to type px;
– 7.7 c) clarify that the instruction label should specify purge time and pressure/flow;
– 18.7 collect marking requirements throughout the document in the “Marking” clause.
This European Standard is to be read in conjunction with EN 60079-0:2006.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2008-08-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2010-11-01
This European Standard was prepared under a mandate given to CENELEC by the European
Commission and the European Free Trade Association and supports the essential requirements of
Directive 94/9/EC. See Annex ZZ.
Annexes ZA and ZZ have been added by CENELEC.
__________
- 3 - EN 60079-2:2007
Endorsement notice
The text of the International Standard IEC 60079-2:2007 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:
Harmonized in EN 60051 series (not modified).
IEC 60051 NOTE
IEC 60079-1 NOTE Harmonized as EN 60079-1:2007 (not modified).
IEC 60079-5 NOTE Harmonized as EN 60079-5:2007 (not modified).
IEC 60079-6 NOTE Harmonized as EN 60079-6:2007 (not modified).
IEC 60079-7 NOTE Harmonized as EN 60079-7:2007 (not modified).
Harmonized as EN 60079-11:2007 (not modified).
IEC 60079-11 NOTE
Harmonized as EN 60079-15:2005 (not modified).
IEC 60079-15 NOTE
IEC 60079-18 NOTE Harmonized as EN 60079-18:2004 (not modified).
IEC 60079-26 NOTE Harmonized as EN 60079-26:2007 (not modified).
IEC 60079-28 NOTE Harmonized as EN 60079-28:2007 (not modified).
__________
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

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.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year

1) 2)
IEC 60034-5 – Rotating electrical machines - EN 60034-5 2001
Part 5: Degrees of protection provided by the
integral design of rotating electrical machines
(IP code) - Classification
1)
IEC 60050-151 – International Electrotechnical Vocabulary - – –
Part 151: Electrical and magnetic devices

1)
IEC 60050-426 – International Electrotechnical Vocabulary - – –
Chapter 426: Electrical apparatus for
explosive atmospheres
IEC 60079-0 2004 Electrical apparatus for explosive gas EN 60079-0 2006
(mod) atmospheres -
Part 0: General requirements
1) 2)
IEC 60112 – Method for the determination of the proof EN 60112 2003
and the comparative tracking indices of solid
insulating materials
1) 2)
IEC 60529 – Degrees of protection provided by EN 60529 1991
enclosures (IP Code) + corr. May 1993

3)
IEC 60664-1 1992 Insulation coordination for equipment within EN 60664-1 2003
low-voltage systems -
Part 1: Principles, requirements and tests

1)
Undated reference.
2)
Valid edition at date of issue.
3)
EN 60664-1:2003, which includes A1:2000 + A2:2002 to IEC 60664-1:1992, is superseded by EN 60664-1:2007,
which is based on IEC 60664-1:2007.

- 5 - EN 60079-2:2007
Annex ZZ
(informative)
Coverage of Essential Requirements of EC Directives

This European Standard has been prepared under a mandate given to CENELEC by the European
Commission and the European Free Trade Association and within its scope the standard covers only the
following essential requirements out of those given in Annex II of the EC Directive 94/9/EC:
– ER 1.0.1 to ER 1.0.6;
– ER 1.2.1, ER 1.2.2 (partly), ER 1.2.3, ER 1.2.6 to ER 1.2.8;
– ER 1.3.1, ER 1.3.5;
– ER 1.4.1 (partly);
– ER 1.5.1 to ER 1.5.8;
– ER 1.6.2 (partly), ER 1.6.3 to ER 1.6.5;
– ER 2.0.2.1, ER 2.0.2.2;
– ER 2.2.1, ER 2.2.1.1 to ER 2.2.1.3;
– ER 2.3.1, ER 2.3.1.1, ER 2.3.1.2.
Compliance with this standard provides one means of conformity with the specified essential
requirements of the Directive concerned.
WARNING: Other requirements and other EC Directives may be applicable to the products falling within
the scope of this standard.
___________
NORME CEI
INTERNATIONALE
IEC
60079-2
INTERNATIONAL
Cinquième édition
STANDARD
Fifth edition
2007-02
Atmosphères explosives –
Partie 2:
Protection du matériel par enveloppe à
surpression interne «p»
Explosive atmospheres –
Part 2:
Equipment protection by pressurized
enclosure «p»
© IEC 2007 Droits de reproduction réservés ⎯ Copyright - all rights reserved
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60079-2 © IEC:2007 – 3 –
CONTENTS
FOREWORD.9
INTRODUCTION.13

1 Scope.15
2 Normative references .15
3 Terms and definitions .17
4 Protection types .21
5 Constructional requirements for pressurized enclosures .27
5.1 Enclosure .27
5.2 Materials .27
5.3 Doors and covers .27
5.4 Mechanical strength .29
5.5 Apertures, partitions, compartments and internal components .29
5.6 Insulating materials .31
5.7 Sealing.31
5.8 Spark and particle barriers .31
5.9 Internal batteries .31
6 Temperature limits.33
6.1 General .33
6.2 For type px or type py.33
6.3 For type pz.33
7 Safety provisions and safety devices (except for static pressurization) .33
7.1 Suitability of safety devices for hazardous area.33
7.2 Integrity of safety devices.33
7.3 Provider of safety devices .35
7.4 Sequence diagram for type px .35
7.5 Ratings for safety devices .35
7.6 Purging automated for type px.35
7.7 Purging criteria.37
7.8 Requirements when a minimum flow rate required.37
7.9 Safety devices to detect overpressure .37
7.10 Value of overpressure .39
7.11 Pressurizing multiple enclosures .41
7.12 Safety devices on doors and covers .41
7.13 Protection types that may remain energized .41
7.14 Protection types permitted within type py.41
8 Safety provisions and safety devices for static pressurization.41
8.1 Suitability of safety devices for hazardous area.41
8.2 Protective gas .43
8.3 Internal sources of release .43
8.4 Filling procedure .43
8.5 Safety devices.43
8.6 Protection types that may remain energized .43
8.7 Overpressure .43

60079-2 © IEC:2007 – 5 –
9 Supply of protective gas .43
9.1 Type of gas .43
9.2 Temperature.45
10 Pressurized equipment with an internal source of release.45
11 Release conditions .45
11.1 No release.45
11.2 Limited release of a gas or vapour.45
11.3 Limited release of a liquid.45
12 Design requirements for the containment system.47
12.1 General design requirements.47
12.2 Infallible containment system .47
12.3 Containment system with a limited release .47
13 Protective gas and pressurizing techniques .49
13.1 General .49
13.2 Pressurization with leakage compensation .51
13.3 Pressurization with dilution.51
14 Ignition-capable apparatus .53
15 Internal hot surfaces.53
16 Type verification and tests.55
16.1 Maximum overpressure test.55
16.2 Leakage test .55
16.3 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 .55
16.4 Purging and dilution tests for a pressurized enclosure with an internal source
of release .57
16.5 Verification of minimum overpressure.61
16.6 Tests for an infallible containment system .61
16.7 Overpressure test for a containment system with a limited release .63
16.8 Verifying ability of the pressurized enclosure to limit internal pressure .63
17 Routine tests .65
17.1 Functional test.65
17.2 Leakage test .65
17.3 Tests for an infallible containment system .65
17.4 Test for a containment system with a limited release .65
18 Marking .65
18.1 Identifying as pressurized.65
18.2 Warnings.65
18.3 Supplementary marking.65
18.4 Internal source of release.67
18.5 Static pressurization.67
18.6 Pressurization systems.67
18.7 Warnings required in other clauses .67
18.8 Overpressure limited by user.67
18.9 Inert gas.69
19 Instructions.69

60079-2 © IEC:2007 – 7 –
Annex A (normative) Purging and dilution tests.71
Annex B (informative) Examples of functional sequence diagram.75
Annex C (informative) Examples of the changes in pressure in ducts and enclosures .79
Annex D (informative) Information to be provided to the user .89
Annex E (normative) Classification of the type of release within enclosures .93
Annex F (informative) Examples for the use of the dilution area concept.95
Annex G (normative) Infallibility test for containment system.99
Annex H (informative) Introduction of an alternative risk assessment method
encompassing “equipment protection levels” for Ex equipment .101

Bibliography.111

Figure B.1 – State diagram of a leakage-compensation purge control system .75
Figure C.1 a) – Protective gas outlet without a spark and particle barrier .79
Figure C.1 b) – Protective gas outlet with a spark and particle barrier.81
Figure C.2 – Pressurized enclosures with leakage compensation, enclosures without
moving parts .83
Figure C.3 – Pressurized enclosures with leakage compensation, rotating electrical
machine with an internal cooling fan .85
Figure C.4 – Pressurized enclosure with a leakage compensation, rotating electrical
machine with an external cooling fan .87
Figure F.1 – Diagram showing the use of the dilution area concept to simplify the purge
and dilution test requirements .95
Figure F.2 – Diagram showing the use of the infallible containment system concept to
simplify the purging and dilution requirements around ICA.97
Figure F.3 – Diagram showing the use of internal partitions around the potential source
of release to simplify the purging and dilution requirements around ICA located outside
the partitions.97
Figure G.1 – Schematic diagram of the infallibility test described in 16.6.2 a) .99

Table 1 – Determination of protection type.23
Table 2 – Design criteria based upon type of protection.25
Table 3 – Safety devices based upon protection type.35
Table 4 – Protective gas requirements for a pressurized enclosure with a containment
system .49
Table 5 – Protection types permitted within the dilution area.53
Table B.1 – Truth table of a leakage-compensation purge control system .75
Table H.1 – Traditional relationship of EPLs to zones (no additional risk assessment) .105
Table H.2 – Description of risk of ignition protection provided .107

60079-2 © IEC:2007 – 9 –
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
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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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 60079-2 has been prepared by technical committee 31: Explosive
atmospheres.
This fifth edition cancels and replaces the fourth edition published in 2001 and constitutes a
technical revision.
The significant changes with respect to the previous edition are listed below:
− Introduction of the “Equipment protection level concept” – See Annex H.
–  3.13  Eliminate reference to “room” in the definition of pressurization.
–  5.3.3 Restrict to type px.
–  5.3.3 Add warning for type pz and type py for any cover removable without the use
of a tool.
60079-2 © IEC:2007 – 11 –
–   7.6 Move wording “For type px” to beginning of subclause to clarify 7.6 only
applies to type px.
–   7.7 c) Clarify that the instruction label should specify purge time and pressure/flow.
–  18.7 Collect marking requirements throughout the document in the “Marking”
clause.
The text of this standard is based on the following documents:
FDIS Report on voting
31/668/FDIS 31/681/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 standard is to be read in conjunction with IEC 60079-0:2004, Electrical apparatus for
explosive gas atmospheres – Part 0: General requirements.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of IEC 60079 series, under the general title Explosive atmospheres can be
found on the IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the new edition.
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.
60079-2 © IEC:2007 – 13 –
INTRODUCTION
This part of IEC 60079 gives requirements for the design, construction, testing and marking of
electrical apparatus for use in potentially explosive atmospheres in which
a) a protective gas maintained at a pressure above that of the external atmosphere is used to
guard against the formation of an explosive gas atmosphere within enclosures which do
not contain an internal source of release of flammable gas or vapour and, where
necessary;
b) a protective gas is provided in sufficient quantity to ensure that the resultant mixture
concentration around the electrical parts is maintained at a value outside the explosive
limit appropriate to the particular conditions of use. The protective gas is supplied to an
enclosure containing one or more internal sources of release in order to guard against the
formation of an explosive gas atmosphere.
This standard includes requirements for the apparatus and its associated equipment including
the inlet and exhaust ducts, and also for the auxiliary control apparatus necessary to ensure
that pressurization and/or dilution is established and maintained.

60079-2 © IEC:2007 – 15 –
EXPLOSIVE ATMOSPHERES –
Part 2: Equipment protection by pressurized enclosure "p"

1 Scope
This part of IEC 60079 contains the specific requirements for the construction and testing of
electrical apparatus with pressurized enclosures, of type of protection “p”, intended for use in
explosive gas atmospheres. It specifies requirements for pressurized enclosures containing a
limited release of a flammable substance.
This standard supplements and modifies the general requirements of IEC 60079-0. Where a
requirement of this standard conflicts with a requirement of IEC 60079-0, the requirements of
this standard takes precedence.
This standard does not contain the requirements for:
• pressurized enclosures where the containment system may release
a) air with an oxygen content greater than normal, or
b) oxygen in combination with inert gas in a proportion greater than 21 %;
• pressurized rooms or analyser houses; see IEC 60079-13 and IEC 60079-16.
NOTE 1 Due to the safety factors incorporated in the type of protection, the uncertainty of measurement inherent
in good quality, regularly calibrated measurement equipment is considered to have no significant detrimental effect
and need not be taken into account when making the measurements necessary to verify compliance of the
equipment with the requirements of this standard.
NOTE 2 When the user acts in the role of the manufacturer, it is typically the user’s responsibility to ensure that
all relevant parts of this standard are applied to the manufacturing and testing of the equipment.
NOTE 3 Types of protection “px” and “py”provide Equipment Protection Levels (EPL) Mb or Gb. Type of protection
“pz” provides Equipment Protection Level (EPL) Gc. For further information, see Annex H.
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 60034-5, Rotating electrical machines – Part 5: Degrees of protection provided by the
integral design of rotating electrical machines (IP code)– Classification
IEC 60050(151), International Electrotechnical Vocabulary – Chapter 151: Electrical and
magnetic devices
IEC 60050(426), International Electrotechnical Vocabulary – Chapter 426: Electrical
apparatus for explosive atmospheres
IEC 60079-0:2004, Electrical apparatus for explosive gas atmospheres – Part 0: General
requirements
60079-2 © IEC:2007 – 17 –
IEC 60112, Method for the determination of the proof and the comparative tracking indices of
solid insulating materials
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60664-1:1992, Insulation coordination for equipment within low-voltage systems – Part 1:
Principles, requirements and tests
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050(151),
IEC 60050(426) and IEC 60079-0, as well as the following apply.
NOTE Unless otherwise specified, the terms "voltage" and "current" mean the r.m.s. values of an alternating,
direct or composite voltage or current.
3.1
alarm
piece of apparatus that generates a visual or audible signal that is intended to attract
attention
3.2
containment system
part of the apparatus containing the flammable substance that may constitute an internal
source of release
3.3
dilution
continuous supply of a protective gas, after purging, at such a rate that the concentration of a
flammable substance inside the pressurized enclosure is maintained at a value outside the
explosive limits at any potential ignition source (that is to say, outside the dilution area)
NOTE Dilution of oxygen by inert gas may result in a concentration of flammable gas or vapour above the upper
explosive limit (UEL).
3.4
dilution area
area in the vicinity of an internal source of release where the concentration of a flammable
substance is not diluted to a safe concentration
3.5
enclosure volume
volume of the empty enclosure without internal apparatus. For rotating electrical machines,
the free internal volume plus the volume displaced by the rotor
3.6
flammable substance
gases, vapours, liquids or mixtures thereof that are capable of being ignited
3.7
hermetically sealed device
device which is so constructed that the external atmosphere cannot gain access to the interior
and in which any seal is made by fusion, for example, brazing, welding or the fusion of glass
to metal
60079-2 © IEC:2007 – 19 –
3.8
ignition-capable apparatus (ICA)
apparatus which in normal operation constitutes a source of ignition for a specified explosive
gas atmosphere. This includes electrical apparatus not protected by a type of protection listed
in 7.13
3.9
indicator
piece of apparatus that shows whether flow or pressure is adequate and is monitored
periodically, consistent with the requirement of the application
3.10
internal source of release
point or location from which a flammable substance in the form of a flammable gas or vapour
or liquid may be released into the pressurized enclosure such that in the presence of air an
explosive gas atmosphere could be formed
3.11
leakage compensation
providing a flow of protective gas sufficient to compensate for any leakage from the
pressurized enclosure and its ducts
3.12
overpressure
pressure above ambient pressure within a pressurized enclosure
3.13
pressurization
technique of guarding against the ingress of the external atmosphere into an enclosure by
maintaining a protective gas therein at a pressure above that of the external atmosphere
3.14
pressurization system
grouping of safety devices and other components used to pressurize and monitor or control a
pressurized enclosure
3.15
pressurized enclosure
enclosure in which a protective gas is maintained at a pressure greater than that of the
external atmosphere
3.16
protective gas
air or inert gas used for purging and maintaining an overpressure and, if required, dilution
NOTE For the purposes of this standard, inert gas means nitrogen, carbon dioxide, argon or any gas which, when
mixed with oxygen in the ratio 4 parts inert to 1 part oxygen as found in air, does not make the ignition and
flammability properties, such as explosive limits, more onerous.
3.17
protective gas supply
compressor, blower or compressed gas container that provides the protective gas at a
positive pressure. The supply includes inlet (suction) pipes or ducts, pressure regulators,
outlet pipes, ducts, and supply valves. Components of the pressurization system are not
included
60079-2 © IEC:2007 – 21 –
3.18
purging
in a pressurized enclosure, the operation of passing a quantity of protective gas through the
enclosure and ducts, so that the concentration of the explosive gas atmosphere is brought to
a safe level
3.19
routine test
test to which each individual device (equipment) is subjected during or after manufacture to
ascertain whether it complies with certain criteria
[IEV 151-04-16, modified]
3.20
static pressurization
maintenance of an overpressure within a pressurized enclosure without the addition of
protective gas in a hazardous area
3.21
type px
pressurization that reduces the equipment protection level within the pressurized enclosure
from Gb to non-hazardous or Mb to non-hazardous
3.22
type py
pressurization that reduces the equipment protection level within the pressurized enclosure
from Gb to Gc
3.23
type pz
pressurization that reduces the equipment protection level within the pressurized enclosure
from Gc to non-hazardous
3.24
type test
test of one or more devices made to a certain design to show that the design meets certain
specifications
[IEV 151-04-15]
3.25
safety device
device used to implement or maintain the integrity of the type of protection
4 Protection types
Protection by pressurization is subdivided into three types of protection (px, py and pz) which
are selected based upon the equipment protection level required for the external explosive
gas atmosphere (Mb, Gb or Gc), whether there is the potential for an internal release, and
whether the equipment within the pressurized enclosure is ignition-capable; see Table 1. The
type of protection then defines design criteria for the pressurized enclosure and the
pressurization system; see Table 2.

60079-2 © IEC:2007 – 23 –
Table 1 – Determination of protection type
Flammable substance in the Equipment protection Enclosure contains Enclosure does not
containment system level requirement for ignition-capable apparatus contain ignition-capable
external explosive gas apparatus
atmosphere
a
No containment system Gb or Mb Type px  Type py
No containment system Gc Type pz No pressurization required
a
Gas/vapour Gb or Mb Type px Type py
b
Gas/vapour Gc Type px (and ignition- Type py
capable apparatus is not
located in the dilution area)
a c
Liquid Gb Type px (inert) Type py
c
Liquid Gc Type pz (inert) No pressurization
d
required
NOTE If the flammable substance is a liquid, normal release is never permitted.
a
Type of protection px also applies to group I.
b
If no normal release; see Annex E.
c
The protective gas shall be inert if "(inert)" is shown after the pressurization type; see Clause 13.
d
Protection by pressurization is not required since it is considered unlikely that a fault causing a release of liquid
will simultaneously occur with a fault in the equipment that would provide an ignition source.

60079-2 © IEC:2007 – 25 –
Table 2 – Design criteria based upon type of protection
Type pz with
Design criteria Type px Type py Type pz with alarm
indicator
Degree of enclosure IP4X minimum IP4X minimum IP4X minimum IP3X minimum
protection according to
IEC 60529 or
IEC 60034-5
Resistance of enclosure to IEC 60079-0, Table 8 IEC 60079-0, IEC 60079-0, Table 8 IEC 60079-0, half the
impact Table 8 value in Table 8
Verifying purge period Requires a timing Time and flow Time and flow Time and flow
device and marked marked marked
monitoring of
pressure and flow
Preventing incandescent Spark and particle No requirement, Spark and particle Spark and particle
particles from exiting a barrier required, see see Note 1 barrier required, barrier required,
normally closed relief vent 5.8, unless see 5.8, unless see 5.8, unless
into an area requiring EPL incandescent incandescent incandescent
Gb or Mb particles not normally particles not normally particles not normally
produced produced produced
Preventing incandescent No requirement, see No requirement, No requirement, see No requirement, see
particles from exiting a Note 2 see Note 2 Note 2 Note 2
normally closed relief vent
into an area requiring EPL
Gc
Preventing incandescent Spark and particle Spark and Spark and particle Spark and particle
particles from exiting a barrier required, particle barrier barrier required; barrier required,
vent that opens during see 5.8 required, see 5.8 see 5.8
normal operation, to an see 5.8

area requiring EPL Gb or
Mb
Preventing incandescent Spark and particle No requirement, Spark and particle Spark and particle
particles from exiting a barrier required, see see Note 1 barrier required, see barrier required, see
vent that opens during 5.8, unless 5.8, unless 5.8, unless
normal operation to an incandescent incandescent incandescent
area requiring EPL Gc particles not normally particles not normally particles not normally
produced produced produced
Door or cover removable Warning, see 5.3 and Warning, see Warning, see 5.3.6 Warning, see 5.3.6
only with use of a tool 6.2 b) ii) 5.3.6 and Note and Note 3 and Note 3
Door or cover removable Interlock, see 7.12 Warning, see Warning, see 5.3.6 Warning, see 5.3.6
without use of a tool 5.3.6 and Note and Note 3 and Note 3
(no internal hot parts)
Internal hot parts that Comply with 6.2 b) ii) No requirement, Warning, see 5.3.6 Warning, see 5.3.6
require a cool-down period see Note 1
before opening enclosure
NOTE 1 Subclause 6.2 b) ii) is not applicable for type py since neither hot internal parts nor normally created
incandescent particles are permitted.
NOTE 2 There is no requirement for spark and particle barriers since in abnormal operation, where the relief vent
opens, it is unlikely that the external atmosphere is within the explosive limits.
NOTE 3 There is no requirement for tool accessibility on a type of protection pz enclosure since in normal
operation the enclosure is pressurized with all covers and doors in place. If a cover or door is removed, it is unlikely
that the atmosphere is within the explosive limits.

60079-2 © IEC:2007 – 27 –
5 Constructional requirements for pressurized enclosures
5.1 Enclosure
The pressurized enclosure shall have a degree of protection in accordance with Table 2.
NOTE The degree of protection of IP44 may be required on a coal face under humid and dusty conditions.
5.2 Materials
The materials used for the enclosure, ducts and connecting parts shall not be adversely
affected by the specified protective gas.
5.3 Doors and covers
5.3.1 Group I pressurized enclosures
Doors and covers shall either
– have special fasteners complying with IEC 60079-0,
...