IEC 60079-28:2015

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
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.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé Fax: +41 22 919 03 00
CH-1211 Geneva 20 info@iec.ch
Switzerland www.iec.ch
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.

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.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing more than 30 000 terms and
Technical Specifications, Technical Reports and other definitions in English and French, with equivalent terms in 15
documents. Available for PC, Mac OS, Android Tablets and additional languages. Also known as the International
iPad. Electrotechnical Vocabulary (IEV) online.

IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a More than 60 000 electrotechnical terminology entries in
variety of criteria (reference number, text, technical English and French extracted from the Terms and Definitions
committee,…). It also gives information on projects, replaced clause of IEC publications issued since 2002. Some entries
and withdrawn publications. have been collected from earlier publications of IEC TC 37,

77, 86 and CISPR.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: csc@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Catalogue IEC - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
Application autonome pour consulter tous les renseignements
Le premier dictionnaire en ligne de termes électroniques et
bibliographiques sur les Normes internationales,
électriques. Il contient plus de 30 000 termes et définitions en
Spécifications techniques, Rapports techniques et autres
anglais et en français, ainsi que les termes équivalents dans
documents de l'IEC. Disponible pour PC, Mac OS, tablettes
15 langues additionnelles. Egalement appelé Vocabulaire
Android et iPad.
Electrotechnique International (IEV) en ligne.

Recherche de publications IEC - www.iec.ch/searchpub
Glossaire IEC - std.iec.ch/glossary
Plus de 60 000 entrées terminologiques électrotechniques, en
La recherche avancée permet de trouver des publications IEC
en utilisant différents critères (numéro de référence, texte, anglais et en français, extraites des articles Termes et
comité d’études,…). Elle donne aussi des informations sur les Définitions des publications IEC parues depuis 2002. Plus
projets et les publications remplacées ou retirées. certaines entrées antérieures extraites des publications des

CE 37, 77, 86 et CISPR de l'IEC.
IEC Just Published - webstore.iec.ch/justpublished

Service Clients - webstore.iec.ch/csc
Restez informé sur les nouvelles publications IEC. Just
Published détaille les nouvelles publications parues. Si vous désirez nous donner des commentaires sur cette
Disponible en ligne et aussi une fois par mois par email. publication ou si vous avez des questions contactez-nous:
csc@iec.ch.
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 .
...