IEC 60079-28:2006/ISH2:2019

 IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
IEC 60079-28
Edition 1.0  2006-08
EXPLOSIVE ATMOSPHERES –
Part 28: Protection of equipment and
transmission systems using optical radiation

INTERPRETATION SHEET 2
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
31/1495/DISH 31/1509/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.

___________
Interpretation sheet to the scope of IEC 60079-28:2006 (Edition 1) and to the I-SH 01

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 which does not.
This interpretation is made available for Edition 1 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
IEC 60079-28:2006-08/ISH2:2019-10(en)

– 2 – IEC 60079-28:2006/ISH2:2019

 IEC 2019
Details of interpretation:
IEC 60079-28:2006 (Edition 1): Protection of equipment and transmission systems using

optical radiation
Interpretation of the Scope:
Question: The Scope does not describe the applicability of the standard related to

equipment. With the I-SH 01, an interpretation of the Scope was given. However, it is possible

that IEC 60079-28 is not applied in all situations where it is relevant.

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” of IEC 60079-0:2017?
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 1 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 2 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).
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 3 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 4 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 5 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 6 A dust protection “t” enclosure is suitable because there is protection against ingress of an
explosive dust atmosphere.
IEC DISH 60079-28:2006/ISH2 – 3 –

 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 7 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.

 IEC 2019
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE

____________
IEC 60079-28
Edition 1.0  2006-08
ATMOSPHÈRES EXPLOSIVES –
Partie 28: Protection du matériel et des systèmes
de transmission utilisant le rayonnement optique

FE U I LLE D' I NT E RP R É TA TI O N 2

Cette feuille d’inte
...