IEC 60079-28:2015

Explosive atmospheres - Part 28: Protection of equipment and transmission systems using optical radiation

IEC 60079-28:2015 specifies the requirements, testing and marking of equipment emitting optical radiation intended for use in explosive atmospheres. It also covers equipment located outside the explosive atmosphere or protected by a Type of Protection listed in IEC 60079-0, but which generates optical radiation that is intended to enter an explosive atmosphere. It covers Groups I, II and III, and EPLs Ga, Gb, Gc, Da, Db, Dc, Ma and Mb. This standard does not cover ignition by ultraviolet radiation and by absorption of the radiation in the explosive mixture itself. Explosive absorbers or absorbers that contain their own oxidizer as well as catalytic absorbers are also outside the scope of this standard. This second edition cancels and replaces the first edition, published in 2006, and constitutes a technical revision. Refer to the Foreword of the document for a complete listing of the technical changes between edition 2.0 and previous edition of the document. Keywords: equipment emitting optical radiation intended for use in explosive atmospheres
The Interpretation sheet 1 of November 2019 have been included in this copy.

Atmosphères explosives - Partie 28: Protection du matériel et des systèmes de transmission utilisant le rayonnement optique

L'IEC 60079-28:2015 spécifie les exigences, les essais et le marquage du matériel émettant des rayonnements optiques destiné à être utilisé dans des atmosphères explosives. Elle couvre également le matériel situé à l'extérieur de l'atmosphère explosive ou protégé par un mode de protection indiqué dans l'IEC 60079-0, mais qui génère des rayonnements optiques qui sont destinés à pénétrer dans une atmosphère explosive. Elle couvre les Groupes I, II et III, et les EPL Ga, Gb, Gc, Da, Db, Dc, Ma et Mb. La présente norme ne couvre pas l'inflammation par rayonnement ultraviolet et par absorption du rayonnement dans le mélange explosif lui-même. Les absorbeurs explosifs ou absorbeurs qui contiennent leur propre oxydant/comburant de même que les absorbeurs catalytiques sont également hors du domaine d'application de la présente norme. Cette deuxième édition annule et remplace la première édition, parue en 2006. Cette édition constitue une révision technique. Reportez-vous à l'avant-propos du document pour une liste complète des modifications techniques entre l'édition 2.0 et édition précédente du document. Mots clés: matériel émettant des rayonnements optiques destiné à être utilisé dans des atmosphères explosives.
Le contenu de la feuille d'interprétation 1 de novembre 2019 a été pris en considération.

General Information

• Status: Published
• Publication Date: 26-May-2015
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 29.260.20 - Electrical apparatus for explosive atmospheres
• Technical Committee: TC 31 - Equipment for explosive atmospheres
• Drafting Committee: MT 60079-28 - TC 31/MT 60079-28
• Current Stage: PPUB - Publication issued
• Start Date: 15-Jun-2015
• Completion Date: 27-May-2015

Relations

• Revises: IEC 60079-28:2006/COR1:2010 - Corrigendum 1 - Explosive atmospheres - Part 28: Protection of equipment and transmission systems using optical radiation
• Effective Date: 05-Sep-2023
• Revises: IEC 60079-28:2006/ISH2:2019 - Interpretation Sheet 2 - Explosive atmospheres - Part 28: Protection of equipment and transmission systems using optical radiation
• Effective Date: 05-Sep-2023
• Revised: IEC 60079-28:2015/ISH1:2019 - Interpretation Sheet 1 - Explosive atmospheres - Part 28: Protection of equipment and transmission systems using optical radiation
• Effective Date: 05-Sep-2023
• Revises: IEC 60079-28:2006/ISH1:2014 - Intrepretation Sheet 1 - Explosive atmospheres - Part 28: Protection of equipment and transmission systems using optical radiation
• Effective Date: 05-Sep-2023
• Revises: IEC 60079-28:2006 - Explosive atmospheres - Part 28: Protection of equipment and transmission systems using optical radiation
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 60079-28 ®
Edition 2.0 2015-05
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 28: Protection of equipment and transmission systems using optical
radiation
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

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IEC 60079-28 ®
Edition 2.0 2015-05
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 28: Protection of equipment and transmission systems using optical

radiation
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.260.20 ISBN 978-2-8322-2709-1

 IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
IEC 60079-28
Edition 2.0  2015-05
EXPLOSIVE ATMOSPHERES –
Part 28: Protection of equipment and
transmission systems using optical radiation

INTERPRETATION SHEET 1
This interpretation sheet has been prepared by IEC technical committee 31: Equipment for
explosive atmospheres.
The text of this interpretation sheet is based on the following documents:
DISH Report on voting
31/1496/DISH 31/1508/RVDISH
Full information on the voting for the approval of this interpretation sheet can be found in the
report on voting indicated in the above table.

___________
th
Interpretation sheet to the 6 paragraph of the Scope of IEC 60079-28:2015 (Edition 2)
Various interpretations are being made by IECEx ExCB -and ExTL staff regarding the
consideration of the risk of ignition from optical sources, and the applicability of IEC 60079-28
in the context of Subclause 6.6.4 of IEC 60079-0:2017. In addition to assistance provided to
date on IECEx Decision Sheet DS2018/004, the Liaison with IECEx has indicated that an
interpretation sheet addressing the applicability of IEC 60079-28 is required to clarify which
equipment that falls into the scope and what does not.
This interpretation is made available for Edition 2 of this standard due to the current use of
that standard by manufacturers, conformity assessment schemes and national bodies by
means of this “Interpretation Sheet” as follows:
ICS 29.260.20
– 2 – IEC 60079-28:2015/ISH1:2019
 IEC 2019
Details of interpretation:
optical radiation
th
Interpretation of the 6 paragraph of the Scope:
th
Question: The 6 paragraph including the items 1) to 5) describes the equipment excepted
from the Scope of this standard. The understanding of the listed exceptions is ambiguous.
Therefore, it is possible that IEC 60079-28 is not applied in all situations where it is relevant.
In addition, the potential confusion can be compounded by the wording of the exceptions.
When should the requirements of IEC 60079-28 be applied to Ex Equipment, including
Equipment assemblies and Ex Components that include an optical radiation source based on
Subclause 6.6.4 “Lasers, luminaries, and other non-divergent continuous wave optical
sources” in IEC 60079-0:2017 (Edition 7)?
Interpretation:
This standard applies to
i) laser equipment; and
ii) optical fibre equipment; and
iii) any other convergent light sources or beams where light is focussed in one single point
within the hazardous area.
NOTE 2 Some optical elements such as lenses and reflectors are able to convert divergent light into a
convergent beam.
This standard does not apply to:
1) laser equipment for EPL Mb, Gb or Gc and Db or Dc applications which complies with
Class 1 limits in accordance with IEC 60825-1; or
NOTE 3 The referenced Class 1 limits are those that involve emission limits below 15 mW measured at a
distance from the optical radiation source in accordance with IEC 60825-1, with this measured distance
reflected in the Ex application.
2) divergent light sources or beams where light is not focussed within the hazardous area; or
3) Single or multiple optical fibre cables not part of optical fibre equipment if the cables:
a) comply with the relevant industrial standards, along with additional protective means,
e.g. robust cabling, conduit or raceway (for EPL Gb, Db, Mb, Gc or Dc); or
b) comply with the relevant industrial standards (for EPL Gc or Dc).; or
4) Optical radiation sources as defined in i. to iii. above where the optical radiation is fully
contained in an enclosure complying with one of the followings Types of Protection
suitable for the EPL, or the minimum ingress protection rating specified:
a) flameproof "d" enclosures (IEC 60079-1); or
NOTE 4 A flameproof “d” enclosure is suitable because an ignition due to optical radiation in combination
with absorbers inside the enclosure is contained.
b) pressurized "p" enclosures (IEC 60079-2); or
NOTE 5 A pressurized “p” enclosure is suitable because there is protection against ingress of an
explosive atmosphere.
c) restricted breathing “nR” enclosure (IEC 60079-15); or
NOTE 6 A restricted breathing “nR” enclosure is suitable because there is protection against ingress of
an explosive atmosphere.
d) dust protection "t" enclosures" (IEC 60079-31); or
NOTE 7 A dust protection “t” enclosure is suitable because there is protection against ingress of an
explosive dust atmosphere.
 IEC 2019
e) an enclosure that provides a minimum ingress protection of IP 6X and where no
internal absorbers are to be expected and complying with “Tests of enclosures” in
IEC 60079-0.
NOTE 8 An enclosure of a minimum ingress protection of IP 6X and complying with “Tests of enclosures”
in IEC 60079-0 is suitable because there is protection against the ingress of absorbers. It is anticipated
that when the enclosures are opened, entrance of any absorbers is avoided.

– 2 – IEC 60079-28:2015 RLV © IEC 2015

CONTENTS
FOREWORD . 4
INTR ODUCTION . 8
1 Scope . 10
2 Normative references. 11
3 Terms and definitions . 12
4 General requirements . 15
4.1 Optical equipment .
4.2 Risk levels .
5 Types of protection . 16
5.1 General . 16
5.2 Requirements for inherently safe optical radiation “op is” . 17
5.2.1 General . 17
5.2.2 Continuous wave radiation . 17
5.2.3 Pulsed radiation . 21
5.2.4 Ignition tests . 23
5.2.5 Optical devices incorporating the inherently safe concept
Over-power/energy fault protection . 23
5.3 Requirements for protected optical radiation “op pr” . 24
5.3.1 General . 24
5.3.2 Radiation inside optical fibre or cable , etc. (no mechanical damage to
be expected) . 24
5.3.3 Radiation inside enclosures . 25
5.4 Optical radiation system with interlock with optical fibre breakage “op sh” . 25
5.5 Suitability of types of protection .
6 Type verifications and tests . 28
6.1 Test set-up for ignition tests . 28
6.1.1 General . 28
6.1.2 Energy and power measurements .
6.1.2 Test vessel . 28
6.1.3 Ignition criterion Criteria to determine ignition . 28
6.1.4 Mixture temperature .
6.1.5 Mixture pressure .
6.1.6 Safety factor .
6.2 Reference test Verification of suitability of test set-up for type tests . 29
6.2.1 Reference gas . 29
6.2.2 Reference absorber . 29
6.2.3 Reference test for continuous wave radiation and pulses above 1 s
duration . 29
6.2.4 Reference test for pulsed radiation below 1 ms pulse duration . 30
6.3 Test mixture Type tests . 30
6.3.1 Ignition tests with continuous wave radiation and pulses above 1 s
duration . 30
6.3.2 Ignition tests with single pulses less than 1 ms duration . 30
6.3.3 Tests for pulse trains and pulses from 1 ms to 1 s duration . 31
6.3.4 Absorber targets for type tests . 31
6.3.5 Test acceptance criteria and safety factors . 32

6.4 Tests for pulse trains and pulses between 1 ms and 1 s duration .
7 Marking . 32
7.1 General .
7.2 Marking information .
7.3 Examples
...

IEC 60079-28 ®
Edition 2.0 2015-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 28: Protection of equipment and transmission systems using optical
radiation
Atmosphères explosives –
Partie 28: Protection du matériel et des systèmes de transmission utilisant le
rayonnement optique
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
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About the IEC
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International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

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IEC 60079-28 ®
Edition 2.0 2015-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 28: Protection of equipment and transmission systems using optical

radiation
Atmosphères explosives –
Partie 28: Protection du matériel et des systèmes de transmission utilisant le

rayonnement optique
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-2679-7

 IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
IEC 60079-28
Edition 2.0  2015-05
EXPLOSIVE ATMOSPHERES –
Part 28: Protection of equipment and
transmission systems using optical radiation

INTERPRETATION SHEET 1
This interpretation sheet has been prepared by IEC technical committee 31: Equipment for
explosive atmospheres.
The text of this interpretation sheet is based on the following documents:
DISH Report on voting
31/1496/DISH 31/1508/RVDISH
Full information on the voting for the approval of this interpretation sheet can be found in the
report on voting indicated in the above table.

___________
th
Interpretation sheet to the 6 paragraph of the Scope of IEC 60079-28:2015 (Edition 2)
Various interpretations are being made by IECEx ExCB -and ExTL staff regarding the
consideration of the risk of ignition from optical sources, and the applicability of IEC 60079-28
in the context of Subclause 6.6.4 of IEC 60079-0:2017. In addition to assistance provided to
date on IECEx Decision Sheet DS2018/004, the Liaison with IECEx has indicated that an
interpretation sheet addressing the applicability of IEC 60079-28 is required to clarify which
equipment that falls into the scope and what does not.
This interpretation is made available for Edition 2 of this standard due to the current use of
that standard by manufacturers, conformity assessment schemes and national bodies by
means of this “Interpretation Sheet” as follows:
ICS 29.260.20
– 2 – IEC 60079-28:2015/ISH1:2019
 IEC 2019
Details of interpretation:
optical radiation
th
Interpretation of the 6 paragraph of the Scope:
th
Question: The 6 paragraph including the items 1) to 5) describes the equipment excepted
from the Scope of this standard. The understanding of the listed exceptions is ambiguous.
Therefore, it is possible that IEC 60079-28 is not applied in all situations where it is relevant.
In addition, the potential confusion can be compounded by the wording of the exceptions.
When should the requirements of IEC 60079-28 be applied to Ex Equipment, including
Equipment assemblies and Ex Components that include an optical radiation source based on
Subclause 6.6.4 “Lasers, luminaries, and other non-divergent continuous wave optical
sources” in IEC 60079-0:2017 (Edition 7)?
Interpretation:
This standard applies to
i) laser equipment; and
ii) optical fibre equipment; and
iii) any other convergent light sources or beams where light is focussed in one single point
within the hazardous area.
NOTE 2 Some optical elements such as lenses and reflectors are able to convert divergent light into a
convergent beam.
This standard does not apply to:
1) laser equipment for EPL Mb, Gb or Gc and Db or Dc applications which complies with
Class 1 limits in accordance with IEC 60825-1; or
NOTE 3 The referenced Class 1 limits are those that involve emission limits below 15 mW measured at a
distance from the optical radiation source in accordance with IEC 60825-1, with this measured distance
reflected in the Ex application.
2) divergent light sources or beams where light is not focussed within the hazardous area; or
3) Single or multiple optical fibre cables not part of optical fibre equipment if the cables:
a) comply with the relevant industrial standards, along with additional protective means,
e.g. robust cabling, conduit or raceway (for EPL Gb, Db, Mb, Gc or Dc); or
b) comply with the relevant industrial standards (for EPL Gc or Dc).; or
4) Optical radiation sources as defined in i. to iii. above where the optical radiation is fully
contained in an enclosure complying with one of the followings Types of Protection
suitable for the EPL, or the minimum ingress protection rating specified:
a) flameproof "d" enclosures (IEC 60079-1); or
NOTE 4 A flameproof “d” enclosure is suitable because an ignition due to optical radiation in combination
with absorbers inside the enclosure is contained.
b) pressurized "p" enclosures (IEC 60079-2); or
NOTE 5 A pressurized “p” enclosure is suitable because there is protection against ingress of an
explosive atmosphere.
c) restricted breathing “nR” enclosure (IEC 60079-15); or
NOTE 6 A restricted breathing “nR” enclosure is suitable because there is protection against ingress of
an explosive atmosphere.
d) dust protection "t" enclosures" (IEC 60079-31); or
NOTE 7 A dust protection “t” enclosure is suitable because there is protection against ingress of an
explosive dust atmosphere.
 IEC 2019
e) an enclosure that provides a minimum ingress protection of IP 6X and where no
internal absorbers are to be expected and complying with “Tests of enclosures” in
IEC 60079-0.
NOTE 8 An enclosure of a minimum ingress protection of IP 6X and complying with “Tests of enclosures”
in IEC 60079-0 is suitable because there is protection against the ingress of absorbers. It is anticipated
that when the enclosures are opened, entrance of any absorbers is avoided.

– 2 – IEC 60079-28:2015 © IEC 2015
CONTENTS
FOREWORD . 4
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 10
3 Terms and definitions . 10
4 General requirements . 13
5 Types of protection . 13
5.1 General . 13
5.2 Requirements for inherently safe optical radiation “op is” . 14
5.2.1 General . 14
5.2.2 Continuous wave radiation . 14
5.2.3 Pulsed radiation . 18
5.2.4 Ignition tests . 19
5.2.5 Over-power/energy fault protection . 19
5.3 Requirements for protected optical radiation “op pr” . 20
5.3.1 General . 20
5.3.2 Radiation inside optical fibre or cable . 20
5.3.3 Radiation inside enclosures . 21
5.4 Optical system with interlock “op sh” . 21
6 Type verifications and tests . 22
6.1 Test set-up for ignition tests . 22
6.1.1 General .
...