EN 60079-11:2012

Explosive atmospheres - Part 11: Equipment protection by intrinsic safety "i"

NEW! IEC 60079-11:2011 is now available as IEC Standards+ 60079-11:2011 which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition. IEC 60079-11:2011 specifies the construction and testing of intrinsically safe apparatus intended for use in an explosive atmosphere and for associated apparatus, which is intended for connection to intrinsically safe circuits which enter such atmospheres. This type of protection is applicable to electrical equipment in which the electrical circuits themselves are incapable of causing an explosion in the surrounding explosive atmospheres. This standard is also applicable to electrical equipment or parts of electrical equipment located outside the explosive atmosphere or protected by another Type of Protection listed in IEC 60079-0, where the intrinsic safety of the electrical circuits in the explosive atmosphere may depend upon the design and construction of such electrical equipment or parts of such electrical equipment. The electrical circuits exposed to the explosive atmosphere are evaluated for use in such an atmosphere by applying this standard. The requirements for intrinsically safe systems are provided in IEC 60079-25. This standard supplements and modifies the general requirements of IEC 60079-0, except as indicated in Table 1. Where a requirement of this standard conflicts with a requirement of IEC 60079-0, the requirements of this standard shall take precedence. This sixth edition cancels and replaces the fifth edition of IEC 60079-11 published in 2006, the first edition of IEC 61241-11 published in 2005, and partially replaces the second edition of IEC 60079-27 published in 2008 and constitutes a full technical revision. The significant changes with respect to the previous edition are listed below: - Inclusion of non-edition specific references to IEC 60079-0. - The merging of the apparatus requirements for FISCO from IEC 60079-27. - The merging of the requirements for combustible dust atmospheres from IEC 61241-11. - Clarification of the requirements for accessories connected to intrinsically safe apparatus; such as chargers and data loggers. - Addition of new test requirements for opto-isolators. - Introduction of Annex H about ignition testing of semiconductor limiting power supply circuits. The contents of the corrigendum of January 2012 have been included in this copy.

Explosionsgefährdete Bereiche - Teil 11: Geräteschutz durch Eigensicherheit "i"

Atmosphères explosives - Partie 11: Protection de l'équipement par sécurité intrinsèque "i"

NEW! La CEI 60079-11:2011 est maintenant disponible sous forme de IEC Standards+ 60079-11:2011 qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente. La CEI 60079-11:2011 spécifie la construction et les essais pour le matériel électrique de sécurité intrinsèque destiné à être utilisé dans les atmosphères explosives et pour le matériel électrique associé destiné à être relié à des circuits de sécurité intrinsèque qui entrent dans de telles atmosphères. Ce mode de protection s'applique aux équipements électriques dont les circuits sont eux-mêmes incapables de provoquer l'explosion de l'atmosphère environnante. La présente norme s'applique également aux équipements électriques ou aux parties de matériels électriques situés hors de l'atmosphère explosive ou protégés par un autre Mode de Protection cité dans la CEI 60079-0, lorsque la sécurité intrinsèque des circuits électriques situés dans l'atmosphère explosive peut dépendre de la conception et de la construction de ces matériels électriques ou de ces parties de matériels électriques. Les circuits électriques exposés à une atmosphère explosive sont évalués en vue de leur emploi dans une telle atmosphère en appliquant la présente Norme. Les exigences pour les systèmes de sécurité intrinsèque sont données dans la CEI 60079-25. La présente norme complète et modifie les exigences générales de la CEI 60079-0, à l'exception de ce qui est indiqué au Tableau 1. Lorsqu'une exigence de la présente norme entre en conflit avec une exigence de la CEI 60079-0, l'exigence de la présente Norme prévaut. Cette sixième édition annule et remplace la cinquième édition de la CEI 60079-11 publiée en 2006, la première édition de la CEI 61241-11 publiée en 2005, et remplace partiellement la seconde édition de la CEI 60079-27 publiée en 2008 dont elle constitue une révision technique complète. Les modifications importantes par rapport à l'édition antérieure sont indiquées ci-dessous: - Introduction d'une référence à la CEI 60079-0 non spécifique à l'édition; - L'incorporation des exigences de matériel issues de la CEI 60079-27 relatives au FISCO; - L'incorporation des exigences issues de la CEI 61241-11 relatives aux atmosphères de poussières combustibles; - La clarification des exigences relatives aux accessoires reliés à un matériel à sécurité intrinsèque; - tels que les chargeurs et les collecteurs de données; - Ajout de nouvelles exigences d'essai relatives aux isolateurs optiques; - l'introduction d'une Annexe H-au sujet des essais d'inflammation des dispositifs de limitation d'alimentation électrique à semi-conducteur. Le contenu du corrigendum de janvier 2012 a été pris en considération dans cet exemplaire.

Eksplozivne atmosfere - 11. del: Zaščita opreme z lastno varnostjo "i" (IEC 60079-11:2011)

Ta del standarda IEC 60079 določa konstrukcijo in preskušanje lastnovarnih naprav, namenjenih uporabi v eksplozivni atmosferi, in povezanih naprav, namenjenih povezavi z lastnovarnimi tokokrogi, ki vstopajo v take atmosfere. Ta vrsta zaščite se uporablja za električno opremo, v kateri električni tokokrogi sami ne morejo povzročiti eksplozije v okoliških eksplozivnih atmosferah. Ta standard se uporablja tudi za električno opremo ali dele električne opreme, ki je zunaj eksplozivne atmosfere ali jo varuje še ena vrsta zaščite, navedena v standardu IEC 60079-0, pri čemer je lastna varnost električnih tokokrogov v eksplozivni atmosferi lahko odvisna od zasnove in konstrukcije take električne opreme ali delov take električne opreme. Uporaba električnih tokokrogov, izpostavljenih eksplozivni atmosferi, se ovrednoti s tem standardom. Zahteve za lastnovarne sisteme so podane v standardu IEC 60079-25. Ta standard dopolnjuje in spreminja splošne zahteve standarda IEC 60079-0, razen kakor je prikazano v preglednici 1. Kadar je zahteva iz tega standarda v nasprotju z zahtevo iz standarda IEC 60079-0, imajo prednost zahteve iz tega standarda. Če se zahteve iz tega standarda uporabljajo za lastnovarne naprave in povezane naprave, se izraz »naprava« uporablja v celotnem standardu. Ta standard obravnava le električno opremo; zato izraz »oprema«, ki se uporablja v njem, vedno pomeni »električno opremo«. Če v eksplozivno atmosfero postavite povezano napravo, jo je treba zavarovati z ustrezno vrsto zaščite iz standarda IEC 60079-0, zato se zanjo uporabljajo zahteve te metode zaščite in ustrezni deli standarda IEC 60079-0.

General Information

• Status: Published
• Publication Date: 05-Jan-2012
• Withdrawal Date: 03-Aug-2014
• ICS: 29.260.20 - Electrical apparatus for explosive atmospheres
• Technical Committee: CLC/TC 31 - Electrical apparatus for explosive atmospheres - General requirements
• Drafting Committee: CLC/SC 31-3 - Intrinsically safe apparatus and systems “i”
• Parallel Committee: IEC/SC 31G - IEC_SC_31G
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 06-Jan-2012
• Completion Date: 06-Jan-2012
• Directive: 2008/68/EC - Directve 2008/68/EC of the European Parliament and of the council of 24 September 2008 on the inland transport of the dangerous goods
• Directive: 2014/34/EU - Directive 2014/34/EU Of The European Parliament And Of The Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to equipment and protective systems intended for use in potentially explosive atmospheres (recast)
• Directive: 94/9/EC - Directive 94/9/EC of the European Parliament and the Council of 23 March 1994 on the approximation of the laws of the Member States concerning equipment and protective systems intended for use in potentially explosive atmospheres
• Ref Project: SIST EN 60079-11:2012 - Explosive atmospheres - Part 11: Equipment protection by intrinsic safety i (IEC 60079-11:2011)

Relations

• Replaces: EN 60079-27:2008 - Explosive atmospheres - Part 27: Fieldbus intrinsically safe concept (FISCO)
• Effective Date: 29-Jan-2023
• Replaces: EN 60079-11:2007 - Explosive atmospheres - Part 11: Equipment protection by intrinsic safety "i"
• Effective Date: 29-Jan-2023
• Replaces: EN 61241-11:2006 - Electrical apparatus for use in the presence of combustible dust - Part 11: Protection by intrinsic safety "iD"
• Effective Date: 28-Jan-2023
• Replaced By: EN IEC 60079-11:2024 - Explosive atmospheres - Part 11: Equipment protection by intrinsic safety "i"
• Effective Date: 25-Jan-2023

Overview

EN 60079-11:2012 (identical to IEC 60079-11:2011) is the international / European standard for equipment protection by intrinsic safety (type of protection "i") in explosive atmospheres. It specifies construction, testing and marking requirements for intrinsically safe apparatus and associated apparatus intended for use in areas with flammable gases, vapours or combustible dust. This sixth edition consolidates previous related standards (including parts of EN 60079-27 / FISCO and EN 61241-11 for dust) and incorporates new test and accessory guidance (e.g., opto‑isolator tests and Annex H on ignition testing of semiconductor limiting power supply circuits).

Key topics and technical requirements

• Scope and application: Requirements for electrical equipment whose circuits are incapable of causing ignition in explosive atmospheres; also covers equipment outside hazardous areas whose design affects intrinsic safety.
• Grouping & classification: Group and temperature classification for gas and dust hazardous areas; levels of protection "ia", "ib", "ic".
• Ignition compliance: Spark and thermal ignition criteria and component temperature limits for Groups I, II and III.
• Apparatus construction: Rules for enclosures, terminals, plugs/sockets, wiring, encapsulation and polarity protection.
• Separation requirements: Clearance, creepage, composite separations, printed circuit board spacing and dielectric strength.
• Components & connectors: Rating and verification of components, connectors for internal connections and plug-in cards.
• Accessories & associated apparatus: Guidance for chargers, data loggers and equipment connected to intrinsically safe circuits.
• New/merged content: Incorporation of FISCO apparatus requirements and combustible dust provisions; new testing for opto‑isolators and semiconductor limiting power supplies.
• Certification/marking: Examples and relation to EU ATEX directives (standard supports essential requirements of Directive 94/9/EC).

Practical applications

• Design and manufacture of intrinsically safe instruments: sensors, transmitters, portable instruments, control modules and associated peripheral devices.
• Hazardous‑area system design: specifying compatible associated apparatus and circuit parameters to maintain intrinsic safety.
• Conformity assessment and testing: type testing and routine tests performed by test laboratories and notified bodies.
• Procurement and maintenance: ensuring replacement parts and accessories preserve intrinsic safety of installed systems.

Who should use this standard

• Manufacturers of electrical/electronic equipment for hazardous locations
• Safety and instrumentation engineers designing intrinsically safe systems
• Test laboratories, certification bodies and notified bodies (ATEX/IECEx)
• Maintenance, procurement and compliance teams responsible for hazardous‑area equipment

Related standards

• IEC / EN 60079-0 (general requirements for explosive atmospheres)
• IEC / EN 60079-25 (intrinsically safe electrical systems)
• EN 60079-27 (FISCO - now merged where applicable)
• IEC 61241-11 (combustible dust, merged where applicable)

Keywords: EN 60079-11:2012, IEC 60079-11:2011, intrinsic safety, explosive atmospheres, intrinsically safe apparatus, ATEX, FISCO, combustible dust, hazardous area equipment.

Standards Content (Sample)

SLOVENSKI STANDARD
01-marec-2012
1DGRPHãþD
SIST EN 60079-11:2007
SIST EN 60079-27:2008
SIST EN 61241-11:2007
(NVSOR]LYQHDWPRVIHUHGHO=DãþLWDRSUHPH]ODVWQRYDUQRVWMRL,(&

Explosive atmospheres - Part 11: Equipment protection by intrinsic safety i (IEC 60079-
11:2011)
Explosionsgefährdete Bereiche - Teil 11: Geräteschutz durch Eigensicherheit "i" (IEC
60079-11:2011)
Atmosphères explosives - Partie 11: Protection de l'équipement par sécurité intrinsèque
"i" (CEI 60079-11:2011)
Ta slovenski standard je istoveten z: EN 60079-11:2012
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 60079-11
NORME EUROPÉENNE
January 2012
EUROPÄISCHE NORM
ICS 29.260.20 Supersedes EN 60079-11:2007, EN 60079-27:2008 (partially), EN 61241-11:2006

English version
Explosive atmospheres -
Part 11: Equipment protection by intrinsic safety "i"
(IEC 60079-11:2011)
Atmosphères explosives -  Explosionsgefährdete Bereiche -
Partie 11: Protection de l'équipement par Teil 11: Geräteschutz durch
sécurité intrinsèque "i" Eigensicherheit "i"
(CEI 60079-11:2011) (IEC 60079-11:2011)

This European Standard was approved by CENELEC on 2011-08-04. 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, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland, Turkey and the United Kingdom.

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

Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2012 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60079-11:2012 E
Foreword
The text of document 31G/207/FDIS, future edition 6 of IEC 60079-11, prepared by SC 31G,
"Intrinsically-safe apparatus", of IEC/TC 31, "Equipment for explosive atmospheres" was submitted to the
IEC-CENELEC parallel vote and approved by CENELEC as EN 60079-11:2012.

The following dates are fixed:
(dop) 2012-07-06
• latest date by which the document has
to be implemented at national level by
publication of an identical national
standard or by endorsement
(dow) 2014-08-04
• latest date by which the national
standards conflicting with the
document have to be withdrawn
This document supersedes EN 60079-11:2007, EN 61241-11:2006 and partially supersedes
EN 60079-27:2008 (see Annex ZY for significant changes).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent
rights.
This document has been prepared under a mandate given to CENELEC by the European Commission
and the European Free Trade Association, and supports essential requirements of EU Directive(s).

For the relationship with EU Directive(s) see informative Annex ZZ, which is an integral part of this
document.
Endorsement notice
The text of the International Standard IEC 60079-11:2011 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 60079-15 NOTE  Harmonized as EN 60079-15.
IEC 61086-1:2004 NOTE  Harmonized as EN 61086-1:2004 (not modified).
IEC 62133 NOTE  Harmonized as EN 62133.

- 3 - EN 60079-11:2012
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

IEC 60079-0 - Explosive atmospheres - EN 60079-0 -
Part 0: Equipment - General requirements

IEC 60079-7 - Explosive atmospheres - EN 60079-7 -
Part 7: Equipment protection by increased
safety "e"
IEC 60079-25 - Explosive atmospheres - EN 60079-25 -
Part 25: Intrinsically safe electrical systems

IEC 60085 - Electrical insulation - Thermal evaluation and EN 60085 -
designation
IEC 60112 - Method for the determination of the proof and EN 60112 -
the comparative tracking indices of solid
insulating materials
IEC 60127 Series Miniature fuses EN 60127 Series

IEC 60317-3 - Specifications for particular types of winding - -
wires -
Part 3: Polyester enamelled round copper
wire, class 155
IEC 60317-7 - Specifications for particular types of winding HD 555.7 S2 -
wires -
Part 7: Polyimide enamelled round copper
wire, class 220
IEC 60317-8 - Specifications for particular types of winding EN 60317-8 -
wires -
Part 8: Polyesterimide enamelled round
copper wire, class 180
IEC 60317-13 - Specifications for particular types of winding EN 60317-13 -
wires -
Part 13: Polyester or polyesterimide
overcoated with polyamide-imide enamelled
round copper wire, class 200
IEC 60529 - Degrees of protection provided by enclosures - -
(IP Code)
IEC 60664-1 2007 Insulation coordination for equipment within EN 60664-1 2007
low-voltage systems -
Part 1: Principles, requirements and tests

IEC 60664-3 2003 Insulation coordination for equipment within EN 60664-3 2003
low-voltage systems -
Part 3: Use of coating, potting or moulding for
protection against pollution
Publication Year Title EN/HD Year

IEC 61158-2 - Industrial communication networks - Fieldbus EN 61158-2 -
specifications -
Part 2: Physical layer specification and service
definition
IEC 62013-1 - Caplights for use in mines susceptible to EN 62013-1 -
firedamp -
Part 1: General requirements - Construction
and testing in relation to the risk of explosion

ANSI/UL 248-1 - Standard for low-voltage fuses - - -
Part 1: General requirements
- 5 - EN 60079-11:2012
Annex ZY
(informative)
Significant changes between this European Standard and EN 60079-11:2007

This European Standard supersedes EN 60079-11:2007.
The significant changes with respect to EN 60079-11:2007 are as listed below.

Type
Significant Changes Clause Minor and Extension Major
editorial technical
changes changes
Table 1
Inclusion of non-edition specific references to
X
EN 60079-11
e.g. 5.6.5.
The merging of the requirements for combustible
X
6.1.3
dust atmospheres from EN 61241-11
Annex G
The merging of the apparatus requirements for
X
FISCO from EN 60079-27
Clarification of the requirements for accessories 6.2.5
connected to intrinsically safe apparatus such as 7.4.9 X
chargers and data loggers.
10.11
Addition of new test requirements for opto-
X
isolators
Annex H
Introduction of Annex H about ignition testing of
X
semiconductor limiting power supply circuits

NOTE: The technical changes referred include the significant technical changes from the EN
revised but is not an exhaustive list of all modifications from the previous version.
Explanations:
A) Definitions
Minor and editorial changes clarification
decrease of technical requirements
minor technical change
editorial corrections
Changes in a standard classified as ‘Minor and editorial changes’ refer to changes regarding the previous
standard, which modify requirements in an editorial or a minor technical way. Also changes of the wording
to clarify technical requirements without any technical change are classified as ‘Minor and editorial
changes’.
A reduction in level of existing requirement is also classified as ‘Minor and editorial changes’

Extension addition of technical options

Changes in a standard classified as ‘extension’ refers to changes regarding the previous standard, 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 ‘extensions’ will not have to be considered for products in conformity with the preceding edition.

Major technical change addition of technical requirements
increase of technical requirements

Changes in a standard classified as ‘Major technical change’ refer to changes regarding the previous
standard, which add new or increase the level of existing technical requirements, in a way that a product
in conformity with the preceding standard will not always be able to fulfil the requirements given in the
standard. ‘Major technical changes’ have to be considered for products in conformity with the preceding
edition. For every change classified as ‘Major Technical Change’ additional information is provided in
clause B) of the Annex ZY.
Note: These changes represent current technological knowledge . However, these changes should not
normally have an influence on equipment already placed on the market.

B) Information about the background of ‘Major Technical Changes’
None.
Instructions:
The manufacturer or his authorised representative in the Community is to draw up the instructions for use
in the required Community languages.
Marking:
The marking in this standard is to be supplemented/modified by the marking according to Directive
94/9/EC. Examples are given below.

European marking examples
Directive part  Standard part  Equipment example
Ex ia IIC T4
–25 °C ≤ Ta ≤ +50 °C Self-contained intrinsically safe apparatus
II 1G
Ex ib IIB T4 Intrinsically safe apparatus designed to
Ui = 24 V Ii = 80 mA Pi = 0.48 W be connected to other apparatus
II 2G
[Ex ib] I
Associated apparatus
Uo = 20 V Io = 300 mA Po = 1.5 W
I (M2)
Intrinsically safe apparatus Level of
Ex ib [ia IIC Ga] IIB T6 Gb
Protection ‘ib’ with ‘ia’ outputs
II 2 (1) G
Ui = 30 V, Uo = 12 V, Io = 100 mA

Associated apparatus protected by a
Ex db [ia Ga] IIB T4 Gb
flameproof enclosure
II 2 (1) G
Uo = 12 V, Io = 200 mA Po = 0.6 W

see also ATEX Guidelines 10.3 and Annex ZZ.

- 7 - EN 60079-11:2012
Annex ZZ
(informative)
Coverage of Essential Requirements of EU Directives

This European Standard has been prepared under a mandate given to CENELEC by the European Union
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 EU Directive 94/9/EC:

– ER 1.0.1 indent 2, ER 1.0.2 (partly), ER 1.0.3 (partly), ER 1.0.4 (partly), ER 1.0.5 (partly), ER 1.0.6
(partly)
– ER 1.1 (partly)
– ER 1.2.1 (partly), ER 1.2.2 (partly), ER 1.2.4 (partly), ER 1.2.6 (partly), ER 1.2.8 (partly)
– ER 1.3.1 (partly)
– ER 1.4 (partly)
– ER 2.0.1.1 to ER 2.0.1.4
– ER 2.0.2.1 (partly), ER 2.0.2.2, ER 2.0.2.3
– ER 2.1.1.1 to ER 2.1.1.3
– ER 2.1.2.1 to ER 2.1.2.4
– ER 2.2.1.1 to ER 2.2.1.3
– ER 2.2.2.1 to ER 2.2.2.4
– ER 2.3.1.1, ER 2.3.1.2
– ER 2.3.2.1 to ER 2.3.2.3
Compliance with this standard provides one means of conformity with the specified essential
requirements of the Directive[s] concerned.

WARNING: Other requirements and other EU Directives may be applicable to the products falling within
the scope of this standard.
IEC 60079-11 ®
Edition 6.0 2011-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 11: Equipment protection by intrinsic safety "i"

Atmosphères explosives –
Partie 11: Protection de l’équipement par sécurité intrinsèque «i»

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XG
ICS 29.260.20 ISBN 978-2-88912-520-3

– 2 – 60079-11  IEC:2011
CONTENTS
FOREWORD . 7
1 Scope . 9
2 Normative references. 14
3 Terms and definitions . 15
4 Grouping and classification of intrinsically safe apparatus and associated apparatus . 20
5 Levels of protection and ignition compliance requirements of electrical apparatus . 21
5.1 General . 21
5.2 Level of protection "ia" . 21
5.3 Level of protection "ib" . 22
5.4 Level of protection "ic" . 22
5.5 Spark ignition compliance . 22
5.6 Thermal ignition compliance . 22
5.6.1 General . 22
5.6.2 Temperature for small components for Group I and Group II . 23
5.6.3 Wiring within intrinsically safe apparatus for Group I and Group II . 23
5.6.4 Tracks on printed circuit boards for Group I and Group II . 24
5.6.5 Intrinsically safe apparatus and component temperature for Group III . 25
5.7 Simple apparatus . 26
6 Apparatus construction . 27
6.1 Enclosures . 27
6.1.1 General . 27
6.1.2 Enclosures for Group I or Group II apparatus . 27
6.1.3 Enclosures for Group III apparatus . 28
6.2 Facilities for connection of external circuits . 28
6.2.1 Terminals . 28
6.2.2 Plugs and sockets . 31
6.2.3 Determination of maximum external inductance to resistance ratio
(L /R ) for resistance limited power source . 31
o o
6.2.4 Permanently connected cable . 32
6.2.5 Requirements for connections and accessories for IS apparatus when
located in the non-hazardous area . 32
6.3 Separation distances . 33
6.3.1 General . 33
6.3.2 Separation of conductive parts . 33
6.3.3 Voltage between conductive parts . 37
6.3.4 Clearance . 37
6.3.5 Separation distances through casting compound . 37
6.3.6 Separation distances through solid insulation . 38
6.3.7 Composite separations . 38
6.3.8 Creepage distance . 38
6.3.9 Distance under coating . 40
6.3.10 Requirements for assembled printed circuit boards . 40
6.3.11 Separation by earthed screens . 41
6.3.12 Internal wiring . 42
6.3.13 Dielectric strength requirement . 42
6.3.14 Relays . 42
6.4 Protection against polarity reversal . 43

60079-11  IEC:2011 – 3 –
6.5 Earth conductors, connections and terminals . 43
6.6 Encapsulation . 44
6.6.1 General . 44
6.6.2 Encapsulation used for the exclusion of explosive atmospheres . 45
7 Components on which intrinsic safety depends . 45
7.1 Rating of components . 45
7.2 Connectors for internal connections, plug-in cards and components . 46
7.3 Fuses . 46
7.4 Primary and secondary cells and batteries . 47
7.4.1 General . 47
7.4.2 Battery construction . 48
7.4.3 Electrolyte leakage and ventilation . 48
7.4.4 Cell voltages . 49
7.4.5 Internal resistance of cell or battery . 49
7.4.6 Batteries in equipment protected by other types of protection . 49
7.4.7 Batteries used and replaced in explosive atmospheres . 49
7.4.8 Batteries used but not replaced in explosive atmospheres . 50
7.4.9 External contacts for charging batteries. 50
7.5 Semiconductors . 50
7.5.1 Transient effects . 50
7.5.2 Shunt voltage limiters. 50
7.5.3 Series current limiters . 51
7.6 Failure of components, connections and separations. 51
7.7 Piezo-electric devices . 52
7.8 Electrochemical cells for the detection of gases . 52
8 Infallible components, infallible assemblies of components and infallible
connections on which intrinsic safety depends . 53
8.1 Level of Protection “ic” . 53
8.2 Mains transformers . 53
8.2.1 General . 53
8.2.2 Protective measures . 53
8.2.3 Transformer construction . 53
8.2.4 Transformer type tests . 54
8.2.5 Routine test of mains transformers . 54
8.3 Transformers other than mains transformers . 54
8.4 Infallible windings . 55
8.4.1 Damping windings . 55
8.4.2 Inductors made by insulated conductors . 55
8.5 Current-limiting resistors . 56
8.6 Capacitors . 56
8.6.1 Blocking capacitors . 56
8.6.2 Filter capacitors . 57
8.7 Shunt safety assemblies . 57
8.7.1 General . 57
8.7.2 Safety shunts . 57
8.7.3 Shunt voltage limiters. 58
8.8 Wiring, printed circuit board tracks, and connections . 58
8.9 Galvanically separating components . 59
8.9.1 General . 59

– 4 – 60079-11  IEC:2011
8.9.2 Isolating components between intrinsically safe and non-intrinsically
safe circuits . 59
8.9.3 Isolating components between separate intrinsically safe circuits . 59
9 Supplementary requirements for specific apparatus. 60
9.1 Diode safety barriers. 60
9.1.1 General . 60
9.1.2 Construction . 60
9.2 FISCO apparatus . 60
9.3 Handlights and caplights . 61
10 Type verifications and type tests . 61
10.1 Spark ignition test . 61
10.1.1 General . 61
10.1.2 Spark test apparatus . 61
10.1.3 Test gas mixtures and spark test apparatus calibration current . 62
10.1.4 Tests with the spark test apparatus . 63
10.1.5 Testing considerations . 64
10.2 Temperature tests . 65
10.3 Dielectric strength tests. 66
10.4 Determination of parameters of loosely specified components . 66
10.5 Tests for cells and batteries . 66
10.5.1 General . 66
10.5.2 Electrolyte leakage test for cells and batteries . 66
10.5.3 Spark ignition and surface temperature of cells and batteries . 67
10.5.4 Battery container pressure tests . 68
10.6 Mechanical tests . 68
10.6.1 Casting compound . 68
10.6.2 Determination of the acceptability of fuses requiring encapsulation . 68
10.6.3 Partitions . 68
10.7 Tests for intrinsically safe apparatus containing piezoelectric devices . 68
10.8 Type tests for diode safety barriers and safety shunts . 69
10.9 Cable pull test . 70
10.10 Transformer tests . 70
10.11 Optical isolators tests . 70
10.11.1 General . 70
10.11.2 Thermal conditioning, dielectric and carbonisation test . 70
10.11.3 Dielectric and short-circuit test . 72
10.12 Current carrying capacity of infallible printed circuit board connections . 72
11 Routine verifications and tests . 73
11.1 Routine tests for diode safety barriers . 73
11.1.1 Completed barriers . 73
11.1.2 Diodes for 2-diode “ia” barriers. 73
11.2 Routine tests for infallible transformers . 73
12 Marking . 74
12.1 General . 74
12.2 Marking of connection facilities . 74
12.3 Warning markings . 75
12.4 Examples of marking . 75
13 Documentation . 77
Annex A (normative) Assessment of intrinsically safe circuits. 78

60079-11  IEC:2011 – 5 –
Annex B (normative) Spark test apparatus for intrinsically safe circuits . 100
Annex C (informative) Measurement of creepage distances, clearances and separation
distances through casting compound and through solid insulation . 108
Annex D (normative) Encapsulation . 111
Annex E (informative) Transient energy test . 118
Annex F (normative) Alternative separation distances for assembled printed circuit
boards and separation of components . 121
Annex G (normative) Fieldbus intrinsically safe concept (FISCO) – Apparatus
requirements . 125
Annex H (informative) Ignition testing of semiconductor limiting power supply circuits . 130
Bibliography . 141

Figure 1 – Separation of intrinsically safe and non-intrinsically safe terminals . 31
Figure 2 – Example of separation of conducting parts . 36
Figure 3 – Determination of creepage distances . 39
Figure 4 – Creepage distances and clearances on printed circuit boards . 41
Figure 5 – Examples of independent and non-independent connecting elements . 44
Figure A.1 – Resistive circuits . 81
Figure A.2 – Group I capacitive circuits . 82
Figure A.3 – Group II capacitive circuits . 83
Figure A.4 – Inductive circuits of Group II . 84
Figure A.5 – Group I inductive circuits . 85
Figure A.6 – Group IIC inductive circuits . 86
Figure A.7 – Simple inductive circuit . 87
Figure A.8 – Simple capacitive circuit . 87
Figure A.9 – Equivalent capacitance . 99
Figure B.1 – Spark test apparatus for intrinsically safe circuits . 104
Figure B.2 – Cadmium contact disc . 105
Figure B.3 – Wire holder . 105
Figure B.4 – Example of a practical design of spark test apparatus . 106
Figure B.5 – Arrangement for fusing tungsten wires . 107
Figure C.1 – Measurement of clearance . 108
Figure C.2 – Measurement of composite distances . 109
Figure C.3 – Measurement of creepage . 110
Figure C.4 – Measurement of composite creepage . 110
Figure D.1 – Examples of encapsulated assemblies conforming to 6.3.5 and 6.6 . 113
Figure D.2 – Applications of encapsulation using casting compound without an
enclosure . 115
Figure D.3 – Examples of assemblies using moulding conforming to 6.6 . 116
Figure E.1 – Example of test circuit . 119
Figure E.2 – Example of output waveform. 120
Figure G.1 – Typical system . 129
Figure H.1 – Safety factor vs ignition probablity . 140

– 6 – 60079-11  IEC:2011
Table 1 – Applicability of specific clauses of IEC 60079-0 . 9
Table 2 – Temperature classification of copper wiring (in a maximum ambient
temperature of 40 °C) . 24
Table 3 – Temperature classification of tracks on printed circuit boards (in a maximum
ambient temperature of 40 °C) . 25
Table 4 – Maximum permitted power dissipation within a component immersed in dust . 26
Table 5 – Clearances, creepage distances and separations . 35
Table 6 – Minimum foil thickness or minimum wire diameter of the screen in relation to
the rated current of the fuse . 54
Table 7 – Compositions of explosive test mixtures adequate for 1,0 safety factor . 62
Table 8 – Compositions of explosive test mixtures adequate for 1,5 safety factor . 63
Table 10 – Routine test voltages for infallible transformers . 73
Table 11 – Text of warning markings . 75
Table A.1 – Permitted short-circuit current corresponding to the voltage and the
Equipment Group . 88
Table A.2 – Permitted capacitance corresponding to the voltage and the Equipment
Group . 93
Table A.3 – Permitted reduction of effective capacitance when protected by a series
resistance . 99
Table F.1 – Clearances, creepage distances and separations for Level of Protection ”ia”
and “ib” when ingress protected, and special conditions of material and installation are
fulfilled . 123
Table F.2 – Clearances, creepage distances and separations for Level of Protection ”ic”
when ingress is protected by an enclosure or by special conditions of installation . 124
Table G.1 – Assessment of maximum output current for use with ‘ia’ and ‘ib’ FISCO

rectangular supplies . 126
Table G.2 – Assessment of maximum output current for use with ‘ic’ FISCO rectangular
supplies . 126
Table H.1 – Sequence of tests . 133
Table H.2 – Safety factor provided by several explosive test mixtures that may be used
for the tests in Table H.1 . 135
Table H.3 – Example of a Group I circuit with characteristics described by Curve II of
Figure H.1 – This passes the test sequence of Table H.1. 136
Table H.4 – Example of a Group I circuit with characteristics described by Curve III of
Figure H.1 – This does not pass the test sequence of Table H.1 . 138

60079-11 © IEC:2011 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 11: Equipment protection by intrinsic safety "i"

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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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
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Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
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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
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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.
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 60079-11 has been prepared by subcommittee 31G: Intrinsically
safe apparatus, of IEC technical committee 31: Equipment for explosive atmospheres.
This sixth edition cancels and replaces the fifth edition of IEC 60079-11 published in 2006, the
first edition of IEC 61241-11 published in 2005, and the new Annex G replaces the apparatus
requirements of the second edition of IEC 60079-27 published in 2008. This sixth edition
constitutes a technical revision of these publications.
NOTE IEC 60079-25 cancels and replaces the remaining subject matter of IEC 60079-27.
The significant changes with respect to the previous edition are listed below:
• Inclusion of non-edition specific references to IEC 60079-0.
• The merging of the apparatus requirements for FISCO from IEC 60079-27.
• The merging of the requirements for combustible dust atmospheres from IEC 61241-11.

– 8 – 60079-11 © IEC:2011
• Clarification of the requirements for accessories connected to intrinsically safe apparatus;
such as chargers and data loggers.
• Addition of new test requirements for opto-isolators.
• Introduction of Annex H about ignition testing of semiconductor limiting power supply
circuits.
The text of this standard is based on the following documents:
FDIS Report on voting
31G/207/FDIS 31G/213/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 supplements and modifies the general requirements of IEC 60079-0, except as
indicated in Table 1 (see Scope).
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
stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to
the specific publication. At this date, the publication will be
• reconfirmed;
•
...