IEC 60079-0:2007

IEC 60079-0
Edition 5.0 2007-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 0: Equipment – General requirements

Atmosphères explosives –
Partie 0: Matériel – Exigences générales

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IEC 60079-0
Edition 5.0 2007-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 0: Equipment – General requirements

Atmosphères explosives –
Partie 0: Matériel – Exigences générales

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
XD
CODE PRIX
ICS 29.260.20 ISBN 2-8318-9326-7

TC 31/Publication 60079-0 (2007), Fifth edition/I-SH 01
EXPLOSIVE ATMOSPHERES –
Part 0: Equipment –
General requirements
INTERPRETATION SHEET
This interpretation sheet has been prepared by committee 31: Equipment for explosive
atmospheres, of IEC.
The text of this interpretation sheet is based on the following documents:
ISH Report on voting
31/768/ISH 31/779/RVD
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.
___________
Subclauses 26.8 and 26.9 of IEC 60079-0 (2007)
Following the discussions by the TC 31/WG 22 Task Group addressing the repeatability of the
thermal endurance to heat and thermal endurance to cold tests it was proposed that a
tolerance be clarified for the test periods in Edition 6, 31/744/DC was issued and comments
received and resolved as 31/752A/INF.
These interpretations are made available for edition 5 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:
Details of interpretation:
Interpretation of subclause 26.8 Thermal endurance to heat and 26.9 Thermal endurance
to cold of IEC 60079-0 (2007):
Question: As it is unreasonable to consider them to be the exact test time, are the time
frames for the 24 h, 336 h (2 weeks) or 672 h (4 weeks) tests considered to be the minimum
times? If so, what is the maximum time?
Interpretation: The 24 h, 336 h and 672 h values are considered the minimum number of
+2
hours for each of the tests. It is practical that the time periods should not extend beyond 24
+30 +30
h, 336 h, 672 h.
0 0
It is intended that this interpretation will be introduced in IEC 60079-0 Edition 6 and therefore
an Interpretation Sheet will not be required for this or future editions.

November 2008 ICS 29.260.20 French text overleaf

 IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
IEC 60079-0
Edition 5.0  2007-10
EXPLOSIVE ATMOSPHERES –
Part 0: Equipment – General requirements

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
31/1453/DISH 31/1466/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 of Subclause 16.5 of IEC 60079-0:2007
The TC 31/CAG requested (Resolution 2 of 2018-04-19) that WG 22 prepare an interpretation
sheet based on IECEx Decision Sheet DS2018/002 addressing the assignment of entry point
and branching point temperatures of electrical rotating machines.
This interpretation is made available for Edition 5 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 60079-0:2007/ISH2:2019

 IEC 2019
Details of interpretation:
requirements
Interpretation of Subclause 16.5 Temperature at branching point and entry point:

Question: Subclause 16.5 of IEC 60079-0:2007 (Ed. 5) states “When the temperature under

rated conditions is higher than 70 °C at the entry point or 80 °C at the branching point of the

conductors, information shall be marked on the equipment exterior to provide guidance to the

user on the proper selection of cable and cable gland or conductors in conduit.”

It is not normal practice for electrical rotating machines to be tested with the cable entry
devices and cables that might be used in an actual installation, but with the cables available
at the manufacturer’s test area. In many cases, there will be no formal entry device as the
cables will enter via the space reserved for fixing of a gland plate.
How shall the relevant entry point and branching point temperatures be determined?
Interpretation: The use of the maximum internal air space temperature to represent the
maximum service temperature of terminal box gaskets and seals, the cable branching point
temperature, and the entry point temperature reflects the normal practice of testing electrical
rotating machines without prior knowledge of the actual glands and cables to be used for
installation. The production of heat from the electrical rotating machine connections is
generally insignificant with respect to the production of heat from the machine windings and
core.
Further amplification:
1) The entry point of the cable where the temperature is measured should be sealed so far
as possible to ensure that there is minimum air-circulation which can reduce the measured
temperature.
2) This is not intended to apply to any gasket between the terminal box and the frame of the
electrical rotating machine, where higher temperatures may be recorded, but only to the
gasket between the terminal box and its lid.
Although written in the context of electrical rotating machines, there may be other types of
equipment where an equivalent approach is applicable.

– 2 – 60079-0 © IEC:2007
CONTENTS
FOREWORD.8

1 Scope.10
2 Normative references .11
3 Terms and definitions .14
4 Equipment grouping .24
4.1 Group I.24
4.2 Group II.24
4.3 Group III.25
4.4 Equipment for a particular explosive atmosphere.25
5 Temperatures .25
5.1 Environmental influences .25
5.1.1 Ambient temperature .25
5.1.2 External source of heating or cooling.25
5.2 Service temperature .26
5.3 Maximum surface temperature .26
5.3.1 Determination of maximum surface temperature .26
5.3.2 Limitation of maximum surface temperature.26
5.3.3 Small component temperature for Group I or Group II electrical
equipment .27
6 Requirements for all electrical equipment .28
6.1 General .28
6.2 Mechanical strength of equipment .29
6.3 Opening times .29
6.4 Circulating currents .29
6.5 Gasket retention.30
6.6 Electromagnetic and ultrasonic energy radiating equipment .30
6.6.1 Radio frequency sources .30
6.6.2 Lasers or other continuous wave sources .31
6.6.3 Ultrasonic sources .31
7 Non-metallic enclosures and non-metallic parts of enclosures .31
7.1 General .31
7.1.1 Applicability .31
7.1.2 Specification of materials.31
7.1.3 Plastic materials .32
7.1.4 Elastomeric materials .32
7.2 Thermal endurance .32
7.2.1 Tests for thermal endurance .32
7.2.2 Material selection .32
7.3 Resistance to light.33
7.4 Electrostatic charges on external non-metallic materials.33
7.4.1 Applicability .33
7.4.2 Avoidance of a build-up of electrostatic charge on Group I or Group II
electrical equipment .33
7.4.3 Avoidance of a build-up of electrostatic charge on equipment for
Group III .35
7.5 Threaded holes .35

60079-0 © IEC:2007 – 3 –
8 Metallic enclosures and metallic parts of enclosures.35
8.1 Material composition .35
8.1.1 Group I .35
8.1.2 Group II .35
8.1.3 Group III .36
8.2 Threaded holes .36
9 Fasteners .36
9.1 General .36
9.2 Special fasteners.36
9.3 Holes for special fasteners .37
9.3.1 Thread engagement .37
9.3.2 Tolerance and clearance .37
9.3.3 Hexagon socket set screws .38
10 Interlocking devices.38
11 Bushings .38
12 Materials used for cementing.38
13 Ex components.39
13.1 General .39
13.2 Mounting .39
13.3 Internal mounting .39
13.4 External mounting .39
14 Connection facilities and termination compartments .39
14.1 General .39
14.2 Termination compartment.39
14.3 Type of protection .40
14.4 Creepage and clearance .40
15 Connection facilities for earthing or bonding conductors .40
15.1 Equipment requiring earthing.40
15.1.1 Internal.40
15.1.2 External.40
15.2 Equipment not requiring earthing.40
15.3 Size of conductor connection.40
15.4 Protection against corrosion .41
15.5 Secureness of electrical connections.41
16 Entries into enclosures .41
16.1 General .41
16.2 Identification of entries .41
16.3 Cable glands .41
16.4 Blanking elements .42
16.5 Temperature at branching point and entry point.42
16.6 Electrostatic charges of cable sheaths .42
17 Supplementary requirements for rotating electrical machines .43
17.1 Fans and fan hoods.43
17.2 Ventilation openings for external fans.43
17.3 Construction and mounting of the ventilating systems .44
17.4 Clearances for the ventilating system .44
17.5 Materials for external fans and fan hoods .44
17.6 Equipotential bonding conductors.44

– 4 – 60079-0 © IEC:2007
18 Supplementary requirements for switchgear .44
18.1 Flammable dielectric .44
18.2 Disconnectors .44
18.3 Group I – Provisions for locking.45
18.4 Doors and covers .45
19 Supplementary requirements for fuses .45
20 Supplementary requirements for plugs, socket outlets and connectors .45
20.1 Interlocking .45
20.1.1 Explosive gas atmospheres .46
20.1.2 Explosive dust atmospheres .46
20.2 Energized plugs .46
21 Supplementary requirements for luminaires .46
21.1 General .46
21.2 Covers for luminaires of EPL Gb or EPL Db .47
21.3 Covers for luminaires of EPL Gc or EPL Dc.47
21.4 Special lamps.47
22 Supplementary requirements for caplights and handlights .47
22.1 Group I caplights .47
22.2 Group II and Group III caplights and handlights .48
23 Equipment incorporating cells and batteries .48
23.1 General .48
23.2 Batteries.48
23.3 Cell types .48
23.4 Cells in a battery .49
23.5 Ratings of batteries .49
23.6 Interchangeability .49
23.7 Charging of primary batteries.49
23.8 Leakage .49
23.9 Connections .49
23.10 Orientation.50
23.11 Replacement of cells or batteries.50
23.12 Replaceable battery pack .50
24 Documentation .50
25 Compliance of prototype or sample with documents .50
26 Type tests .50
26.1 General .50
26.2 Test configuration.51
26.3 Tests in explosive test mixtures.51
26.4 Tests of enclosures .51
26.4.1 Order of tests .51
26.4.2 Resistance to impact .53
26.4.3 Drop test .54
26.4.4 Acceptance criteria.54
26.4.5 Degree of protection (IP) by enclosures.54
26.5 Thermal tests .55
26.5.1 Temperature measurement.55
26.5.2 Thermal shock test .56
26.5.3 Small component ignition test (Group I and Group II).56

60079-0 © IEC:2007 – 5 –
26.6 Torque test for bushings.57
26.6.1 Test procedure .57
26.6.2 Acceptance criteria.58
26.7 Non-metallic enclosures or non-metallic parts of enclosures.58
26.7.1 General .58
26.7.2 Test temperatures .58
26.8 Thermal endurance to heat.58
26.9 Thermal endurance to cold .59
26.10 Resistance to light .59
26.10.1 Test procedure .59
26.10.2 Acceptance criteria.59
26.11 Resistance to chemical agents for Group I electrical equipment.59
26.12 Earth continuity .60
26.13 Surface resistance test of parts of enclosures of non-metallic materials.61
26.14 Charging tests .62
26.14.1 Introduction .62
26.14.2 Principle of the test .62
26.14.3 Samples and test apparatus .63
26.14.4 Ambient conditions .63
26.14.5 Conditioning .63
26.14.6 Determination of the most efficient charging method .63
26.14.7 Assessment of discharge .65
26.15 Measurement of capacitance .66
26.15.1 Test procedure .66
26.15.2 Acceptance criteria.66
27 Routine tests .66
28 Manufacturer's responsibility .66
28.1 Conformity with the documentation.66
28.2 Certificate .66
28.3 Responsibility for marking .66
29 Marking .67
29.1 Location .67
29.2 General .67
29.3 Ex marking for explosive gas atmospheres .67
29.4 Ex marking for explosive dust atmospheres .69
29.5 Combined types of protection .70
29.6 Multiple types of protection .70
29.7 Ga using two independent Gb types of protection .71
29.8 Ex components .71
29.9 Small equipment and small Ex components .71
29.10 Extremely small equipment and extremely small Ex components .72
29.11 Warning markings.72
29.12 Alternate marking of Equipment Protection Levels (EPLs).72
29.12.1 Alternate marking of type of protection for explosive gas
atmospheres .72
29.12.2 Alternate marking of type of protection for explosive dust
atmospheres .73
29.13 Cells and batteries.73
29.14 Examples of marking .74

– 6 – 60079-0 © IEC:2007
30 Instructions.76
30.1 General .76
30.2 Cells and batteries .77

Annex A (normative) Supplementary requirements for cable glands .78
Annex B (normative) Requirements for Ex components.85
Annex C (informative) Example of rig for resistance to impact test.87
Annex D (informative) Introduction of an alternative risk assessment method
encompassing “equipment protection levels” for Ex equipment .88
Annex E (informative) Motors supplied by converters.93

Bibliography.94

Figure 1 – Tolerances and clearance for threaded fasteners .37
Figure 2 – Contact surface under head of fastener with a reduced shank.38
Figure 3 – Illustration of entry points and branching points .43
Figure 4 – Assembly of test sample for earth-continuity test.61
Figure 5 – Test piece with painted electrodes .62
Figure 6 – Rubbing with a pure polyamide or cotton cloth .64
Figure 7 – Discharging of a container with a probe connected to earth via a 0,1 μF

capacitor.64
Figure 8 – Charging by influence with a d.c. voltage power supply.65
Figure A.1 – Illustration of the terms used for cable glands .78
Figure A.2 – Rounded edge of the point of entry of the flexible cable .79
Figure C.1 – Example of rig for resistance to impact test .87

Table 1 – Ambient temperatures in service and additional marking .25
Table 2 – Classification of maximum surface temperatures for Group II electrical
equipment.27
Table 3a – Assessment of temperature classification according to component size at
40ºC ambient temperature .28
Table 3b – Assessment of temperature classification according to component size –

Variation in maximum power dissipation with ambient temperature .28
Table 4 – Radio frequency power thresholds.30
Table 5 – Radio-frequency energy thresholds .30
Table 6 – Limitation of surface areas .34
Table 7 – Diameter or width of long parts.34
Table 8 – Limitation of thickness of non-metallic layer .34
Table 9 – Minimum cross-sectional area of protective conductors .41
Table 10 – Primary cells .48
Table 11 – Secondary cells.49
Table 12 – Tests for resistance to impact.53
Table 13 – Torque to be applied to the stem of bushing used for connection facilities .58
Table 14 − Text of warning markings .72
Table B.1 – Clauses with which Ex components shall comply .85

60079-0 © IEC:2007 – 7 –
Table D.1 – Traditional relationship of EPLs to zones (no additional risk assessment) .90
Table D.2 – Description of risk of ignition protection provided .91

– 8 – 60079-0 © IEC:2007
INTERNATIONAL ELECTROTECHNICAL COMMISSION
_____________
EXPLOSIVE ATMOSPHERES –
Part 0: Equipment –
General requirements
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 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
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 60079-0 has been prepared by IEC technical committee 31:
Equipment for explosive atmospheres.
This fifth edition cancels and replaces the fourth edition, published in 2004, and constitutes a
full technical revision.
The significant changes with respect to the previous edition are listed below:
• Requirements for explosive dust atmospheres transferred from IEC 61241-0.
• The marking Group “II” alone has been replaced by “IIA”, “IIB”, or “IIC” as many of the
enclosure requirements are now aligned with a specific sub-group.
• Dust groups defined as Group IIIA, IIIB and IIIC.
• Limits for ultrasonic and electromagnetic radiation introduced.

60079-0 © IEC:2007 – 9 –
• Remainder of “electrostatic” requirements transferred from IEC 60079-26.

• Equipment protection levels (EPL) introduced.

• Transition of term from “apparatus” to “equipment” (where appropriate).

The text of this standard is based on the following documents:

FDIS Report on voting
31/708/FDIS 31/718/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 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.
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 a 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.
The contents of the interpretation sheets of November 2008 and April 2019, and the
corrigendum of December 2010 have been included in this copy.

– 10 – 60079-0 © IEC:2007
EXPLOSIVE ATMOSPHERES –
Part 0: Equipment –
General requirements
1 Scope
This part of IEC 60079 specifies the general requirements for construction, testing and
marking of electrical equipment and Ex components intended for use in explosive
atmospheres.
Unless modified by one of the standards supplementing this standard, electrical equipment
complying with this standard is intended for use in hazardous areas in which explosive
atmospheres exist under normal atmospheric conditions of
• temperature –20 °C to +60 °C;
• pressure 80 kPa (0,8 bar) to 110 kPa (1,1 bar); and
• air with normal oxygen content, typically 21 % v/v.
The application of electrical equipment in atmospheric conditions outside this range requires
special consideration and may require additional assessment and testing.
NOTE 1 Al
...