IEC 60079-5:2015

Explosive atmospheres - Part 5: Equipment protection by powder filling "q"

IEC 60079-5:2015 contains specific requirements for the construction, testing and marking of electrical equipment, parts of electrical equipment and Ex components in the type of protection powder filling "q", intended for use in explosive gas atmospheres. This standard supplements and modifies the general requirements of IEC 60079-0. Where a requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of this standard takes precedence. This standard applies to electrical equipment, parts of electrical equipment and Ex components with:
- a rated supply current less than or equal to 16 A;
- a rated supply voltage less than or equal to 1 000 V;
- a rated power consumption less than or equal to 1 000 W. This fourth edition cancels and replaces the third edition, published in 2007, and constitutes a technical revision. Refer to the Foreword of the document for a complete listing of the technical changes between edition 4.0 and previous edition of the document. Keywords: electrical equipment and Ex components in the type of protection powder filling "q"

Atmosphères explosives - Partie 5: Protection du matériel par remplissage pulvérulent "q"

IEC 60079-5:2015 contient les exigences spécifiques de construction, d'essais et de marquage d'appareil électrique, des parties d'appareil électrique et des composants Ex à remplissage pulvérulent, mode de protection "q", destinés à être utilisés dans des atmosphères explosives gazeuses. La présente norme complète et modifie les exigences générales de l'IEC 60079-0. Lorsqu'une exigence de la présente norme diverge d'une exigence de l'IEC 60079-0, l'exigence de cette norme prévaut. La présente norme s'applique aux appareils électriques, aux parties d'appareil électrique et aux composants Ex avec:
- un courant assigné d'alimentation inférieur ou égal à 16 A;
- une tension assignée d'alimentation inférieure ou égale à 1 000 V;
- une puissance consommée assignée inférieure ou égale à 1 000 W. Cette quatrième édition annule et remplace la troisième édition parue en 2007. Cette édition constitue une révision technique. Reportez-vous à l'avant-propos du document pour une liste complète des modifications techniques entre l'édition 4.0 et édition précédente du document. Mots clés: d'appareil électrique et des composants Ex à remplissage pulvérulent, mode de protection "q"

General Information

• Status: Published
• Publication Date: 11-May-2022
• ICS: 29.260.20 - Electrical apparatus for explosive atmospheres
• Technical Committee: TC 31 - Equipment for explosive atmospheres
• Drafting Committee: WG 22 - TC 31/WG 22
• Current Stage: PPUB - Publication issued
• Start Date: 17-Feb-2015
• Completion Date: 15-Feb-2015

Relations

• Amended By: IEC 60079-5:2015/AMD1:2022 - Amendment 1 - Explosive atmospheres - Part 5: Equipment protection by powder filling "q"
• Effective Date: 05-Sep-2023
• Revises: IEC 60079-5:2007 - Explosive atmospheres - Part 5: Equipment protection by powder filling "q"
• Effective Date: 05-Sep-2023

Overview

IEC 60079-5:2015 - "Explosive atmospheres – Part 5: Equipment protection by powder filling 'q'" specifies construction, testing and marking requirements for electrical equipment and Ex components in the type of protection powder filling 'q' intended for use in explosive gas atmospheres. This 4th edition (2015) is a technical revision that supersedes the 2007 edition and supplements the general requirements of IEC 60079-0. Where this standard conflicts with IEC 60079-0, IEC 60079-5 takes precedence. The standard applies to equipment with rated supply current ≤ 16 A, rated voltage ≤ 1000 V and rated power ≤ 1000 W. Type “q” typically provides Equipment Protection Levels EPL Gb or Mb.

Key topics and requirements

The standard covers practical and testable requirements including:

• Constructional requirements
  • Definition and design of the container (housing) and sealing/closing arrangements
  • Filling procedures and handling of powder filling material
  • Material specification and documentation for filling media
• Clearances and distances
  • Required distances through filling material and surrounding free space to prevent ignition
  • Rules for creepage distances and reduced distances in specific situations
• Temperature limitations
  • Maximum temperatures for overload and fault/malfunction conditions and protective measures (fuses, temperature-limiting devices)
• Verifications and tests
  • Type tests (pressure test of container, dielectric strength test of filling material, maximum temperature verification)
  • Routine and batch tests (routine pressure and dielectric tests)
  • Degree of protection (IP) verification for enclosures
• Marking and instructions
  • Mandatory marking and user instructions specific to powder-filled Ex equipment
• Annex A
  • Alternative risk assessment method relating EPLs to hazardous zones

Practical applications and users

IEC 60079-5 is used by:

• Manufacturers and designers of intrinsically safe modules, transformers, relays, fuses, control gear and other Ex components that can be powder-filled
• Certification bodies and testing laboratories performing type and routine testing
• Safety engineers, procurement and maintenance teams specifying compliant equipment for explosive gas atmospheres (chemical, oil & gas, petrochemical, mining)
• Compliance officers aligning product design with IEC 60079 series requirements

Typical items covered include electronic circuits, transformers, protection fuses, relays, intrinsically safe apparatus, switches and associated electrical apparatus when protected by powder filling.

Related standards

• IEC 60079-0 (general requirements)
• IEC 60079-1 (flameproof "d"), IEC 60079-7 (increased safety "e"), IEC 60079-11 (intrinsic safety "i")
• IEC 60529 (IP codes), IEC 60127 (miniature fuses) and transformer safety standards referenced for specific tests

Keywords: IEC 60079-5, explosive atmospheres, powder filling "q", equipment protection, Ex components, EPL Gb, EPL Mb, electrical equipment.

Standards Content (Sample)

IEC 60079-5 ®
Edition 4.1 2022-05
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 5: Equipment protection by powder filling "q"

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IEC 60079-5 ®
Edition 4.1 2022-05
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 5: Equipment protection by powder filling "q"
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.260.20 ISBN 978-2-8322-0347-7

IEC 60079-5 ®
Edition 4.1 2022-05
CONSOLIDATED VERSION
REDLINE VERSION
colour
inside
Explosive atmospheres –
Part 5: Equipment protection by powder filling "q"

– 2 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Constructional requirements . 7
4.1 Containers . 7
4.1.1 Closing and sealing . 7
4.1.2 Pressure test of container . 8
4.1.3 Degree of protection of the container . 8
4.1.4 Filling procedure . 8
4.1.5 Containers that are not external enclosures . 8
4.2 Filling material . 9
4.2.1 Material specification . 9
4.2.2 Documentation . 9
4.2.3 Testing . 9
4.3 Distances . 9
4.3.1 Distances through filling material . 9
4.3.2 Distances surrounding free space . 11
4.4 Connections . 12
4.4.1 Equipment . 12
4.4.2 Ex Components . 12
4.5 Capacitors . 12
4.6 Cells and batteries . 12
4.7 Temperature limitations under overload conditions. 12
4.8 Temperature limitations under malfunction conditions . 12
4.8.1 General . 12
4.8.2 Fuse . 12
4.8.3 Malfunction exclusions . 13
4.8.4 Protective devices for temperature limitation. 16
4.8.5 Power supply prospective short-circuit current . 16
5 Verifications and tests . 16
5.1 Type verifications and tests . 16
5.1.1 Pressure type test of container . 16
5.1.2 Verification of the degree of protection of the enclosure . 17
5.1.3 Dielectric strength Insulation resistance test of the filling material . 17
5.1.4 Maximum temperatures . 17
5.2 Routine verifications and tests . 18
5.2.1 Routine pressure test of container . 18
5.2.2 Dielectric strength Insulation resistance test of the filling material . 18
6 Marking . 19
7 Instructions . 20
Bibliography . 21

Figure 1 – Distances through filling material . 11

© IEC 2022
Figure 2 – Test arrangement for the dielectric strength insulation resistance test of the
filling material . 19

Table 1 – Distances through the filling material . 10
Table 2 – Creepage distances and distances through filling material. 15

– 4 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 5: Equipment protection by powder filling “q”

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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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.
This consolidated version of the official IEC Standard and its amendment has been
prepared for user convenience.
IEC 60079-5 edition 4.1 contains the fourth edition (2015-02) [documents 31/1156/FDIS
and 31/1171/RVD] and its amendment 1 (2022-05) [documents 31/1601/CDV and
31/1171/RVD].
In this Redline version, a vertical line in the margin shows where the technical content
is modified by amendment 1. Additions are in green text, deletions are in strikethrough
red text. A separate Final version with all changes accepted is available in this
publication.
© IEC 2022
International Standard IEC 60079-5 has been prepared by IEC technical committee 31:
Equipment for explosive atmospheres.
This fourth edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
NOTE The technical changes referred to include the significant technical changes in the revised IEC standard, but
they do not form an exhaustive list of all modifications from the previous edition. More guidance may be found by
referring to the redline version of the IEC standard, if available.
Type
Minor and Major
Significant changes Clause/subclause Extension
editorial technical
changes changes
Specific references to IEC 60079-0 have been
reworded so the references to IEC 60079-0 can 4.1.3 4.8 4.8.3 X
be non-dated references
The “housing” surrounding the powder filled
equipment or Ex Component has been
redefined as a “container” to avoid confusion 4.1 X
with the “enclosure” requirements of
IEC 60079-0
A relaxation has been introduced to permit
reduced distances through filling material for
4.3.1 X
instances where there is no adjacent gap in the
container
A relaxation has been introduced to permit the
use of creepage dimensions per IEC 60079-7 4.8.3 X
where CTI is better than 175
An evaluation of joints employed when the
reduced distances according to Table 1 are 5.1.1 X
applied, has been added.
Text for determination of maximum temperature
clarified with respect to overloads and 5.1.4 X
malfunctions
A batch routine test has been introduced 5.2.1 X

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The list of all parts of IEC 60079 series, under the general title Explosive atmospheres, can
be found on the IEC website.
The committee has decided that the contents of the base publication and its amendment will
remain unchanged until the stability date indicated on the IEC web site under 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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
EXPLOSIVE ATMOSPHERES –
Part 5: Equipment protection by powder filling “q”

1 Scope
This part of IEC 60079 contains specific requirements for the construction, testing and
marking of electrical equipment, parts of electrical equipment and Ex components in the type
of protection powder filling “q”, intended for use in explosive gas atmospheres.
NOTE 1 Electrical equipment and Ex components protected by powder filling “q” can contain electronic circuits,
transformers, protection fuses, relays, intrinsically safe electrical apparatus, associated electrical apparatus,
switches, etc.
NOTE 2 Type of protection powder filling “q” provides Equipment Protection Level (EPL) Gb or Mb.
This standard supplements and modifies the general requirements of IEC 60079-0. Where a
requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of
this standard takes precedence.
This standard applies to electrical equipment, parts of electrical equipment and Ex
components with:
– a rated supply current less than or equal to 16 A;
– a rated supply voltage less than or equal to 1 000 V;
– a rated power consumption less than or equal to 1 000 W.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60079-0, Explosive atmospheres – Part 0: Equipment – General requirements
IEC 60079-7, Explosive atmospheres – Part 7: Equipment protection by increased safety "e"
IEC 60079-11, Explosive atmospheres – Part 11: Equipment protection by intrinsic safety "i"
IEC 60127 (all parts), Miniature fuses
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 61558-1, Safety of power transformers, power supplies, reactors and similar products –
Part 1: General requirements and tests
IEC 61558-2-6, Safety of transformers, reactors, power supply units and similar products for
supply voltages up to 1 100 V – Part 2-6: Particular requirements and tests for safety isolating
transformers and power supply units incorporating safety isolating transformers
ISO 2859-1, Sampling procedures for inspection by attributes – Part 1: Sampling schemes
indexed by acceptance quality limit (AQL) for lot-by-lot inspection

© IEC 2022
ISO 3310-1, Test sieves – Technical requirements and testing – Part 1: Test sieves of metal
wire cloth
ISO 3310-2, Test sieves – Technical requirements and testing – Part 2: Test sieves of
perforated metal plate
ISO 2591-1, Test sieving – Methods using test sieves of woven wire cloth and perforated
metal plate
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60079-0 as well as
the following apply.
NOTE Additional definitions applicable to explosive atmospheres can be found in IEC 60050-426.
3.1
powder filling “q”
type of protection in which the parts capable of igniting an explosive gas atmosphere are fixed
in position and completely surrounded by filling material to prevent the ignition of an external
explosive gas atmosphere
Note 1 to entry: The type of protection may not prevent the surrounding explosive gas atmosphere from
penetrating into the equipment and components and being ignited by the circuits. However, due to the small free
volumes in the filling material and due to the quenching of a flame which may propagate through the paths in the
filling material, an external explosion is prevented.
3.2
filling material
solid quartz or solid glass particles
3.3
container (for filling material)
housing immediately surrounding the electrical equipment protected by and containing the
filling material
Note 1 to entry: The container may, in some cases, also be the external enclosure.
4 Constructional requirements
4.1 Containers
4.1.1 Closing and sealing
4.1.1.1 General
Containers of electrical equipment, parts of electrical equipment or Ex components protected
by powder filling ”q” shall be filled and sealed at the time of manufacture. The closing and
sealing shall be the methods of 4.1.1.2 or 4.1.1.3.
4.1.1.2 Containers permanently sealed at the time of manufacture
The container shall be permanently sealed at the time of manufacture and shall not be
capable of being opened without leaving visible evidence that the container has been opened.
The container shall be marked in accordance with Clause 6, item a).
NOTE Suitable techniques that can provide visible evidence of containers being opened are, for example,
welding, soldering, cemented joints, rivets, cementing of screws, or lead-seal safety-wiring of screws.

– 8 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
4.1.1.3 Containers intended to be opened for repair
Electrical equipment, parts of electrical equipment, or Ex components that are designed to be
repaired shall incorporate sealing methods that are capable of being renewed without damage
to the container when the equipment is repaired, re-filled, and re-sealed. The container shall
be marked in accordance with Clause 6, item b).
4.1.2 Pressure test of container
The electrical equipment, parts of electrical equipment or Ex components protected by powder
filling “q” shall meet the pressure test requirements specified in 5.1.1.
4.1.3 Degree of protection of the container
The container of the electrical equipment, parts of electrical equipment, or Ex components
protected by powder filling “q”, in their normal service condition, i.e. with all openings closed
as in normal use, shall comply at least with the degree of protection IP54 as defined in
IEC 60529. If the degree of protection is IP55 or higher, and the container is not hermetically
sealed, the container shall be provided with a breathing device. The container with the
breathing device in place shall comply at least with the degree of protection IP54 according to
IEC 60529. The test shall be conducted on an empty container without the powder filling
installed. At the end of any water ingress tests, no water shall be visible inside the container.
NOTE 1 As the container may need to be destroyed in order to determine the entrance of dust or water, two
separate test samples could be required for the two ingress tests.
NOTE 2 When the container is also the external enclosure, the tests of enclosures requirements of IEC 60079-0
apply.
The ingress protection of containers or parts of electrical equipment protected by powder
filling “q”, intended for use only in clean, dry rooms, may be reduced to degree of protection
IP43. The certificate number of this equipment shall include the "X" suffix in accordance with
the marking requirements of IEC 60079-0, and the Specific Conditions of Use listed on the
certificate shall detail the restrictions of use.
When Ex components protected by powder filling “q” are intended to be mounted inside
another enclosure complying with IEC 60079-0, this outer enclosure shall have a degree of
protection of at least IP54. The IP rating of the inner container does not need to be specified
provided that the Ex component is mounted in a position where it is unlikely to be
contaminated by any small amounts of water that may enter the outer enclosure.
NOTE 3 The impact and drop tests of enclosures from IEC 60079-0 do not generally apply to Ex Components
intended to be mounted inside another enclosure complying with IEC 60079-0, as the external enclosure provides
the protection against impact and drop.
The maximum gap of a container protected by powder filling “q” shall be at least 0,1 mm
smaller than the specified smallest dimension of the filling material.
NOTE 4 The restriction on the size of the gap is intended to reduce the escape of filling material.
4.1.4 Filling procedure
Filling shall be carried out so as not to leave any void within the filling material (for example
by shaking down). The free space within electrical equipment, parts of electrical equipment or
Ex components protected by powder filling “q” shall be effectively filled with filling material
(see also 4.3.2).
4.1.5 Containers that are not external enclosures
The container of type of protection “q” equipment or Ex Component that is installed or
intended to be installed internal to another enclosure is considered the same as that of an Ex
Component.
© IEC 2022
4.2 Filling material
4.2.1 Material specification
The material shall be quartz or solid glass particles.
The material specification shall state that, determined in accordance with the ISO 2591-1
procedure for dry materials, the size of particles are within the following sieve sizes:
– 1 mm nominal aperture sieve in accordance with ISO 3310-1 or ISO 3310-2
– 500 µm nominal aperture sieve in accordance with ISO 3310-1.
4.2.2 Documentation
The documents prepared by the manufacturer in accordance with IEC 60079-0 shall include
the specification of the particle material, the size range of the particles, as well as the filling
process and the measures taken to ensure proper filling.
NOTE It is not a requirement of this standard that conformity to the specification of the particle material and size
range of the particles needs to be verified.
4.2.3 Testing
The filling material shall be subjected to the dielectric strength test specified in 5.1.3.
4.3 Distances
4.3.1 Distances through filling material
Except where specified otherwise in this standard, the minimum distance through the filling
material between electrically conducting parts of the equipment and the container shall
comply with Table 1 and Figure 1. This does not apply to conductors used for field wiring
connections which penetrate the wall of the container.

– 10 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
Table 1 – Distances through the filling material
a b
Voltage a.c. r.m.s. or d.c. Minimum distance Reduced distance
V mm mm
5 1,5
U ≤ 80
U ≤ 100 5 2
U ≤125 5 2
5 2
U ≤ 160
U ≤ 200 5 3
U ≤ 250 5 3
6,3 3
U ≤ 400
8 3
U ≤ 500
U ≤ 800 10 5
U ≤ 1 000 14 5
16 10
U ≤ 1 600
U ≤ 2 500 25 10
U ≤ 3 200 32 10
40 14
U ≤ 4 000
50 14
U ≤ 5 000
U ≤ 6 300 63 25
80 25
U ≤ 8 000
100 40
U ≤ 10 000
a
When determining the required values for creepage and distance, the working voltage may be higher than
the voltage in the table by a factor of 1,1 (see Note).
NOTE The factor of 1,1 recognizes that at many places in a circuit, the working voltage equals the rated
voltage and that there are a number of rated voltages in common use that can be accommodated by the 1,1
factor.
b
To ensure that there is a sufficient path length through the filling material to provide quenching of a flame
from the inside to the outside of the container, the reduced distances shown are permitted only when there
is no adjacent gap in the container that could permit a flame to exit. See Figure 1.

© IEC 2022
top
t
t
conductive (metallic) wall
a
c
gap
gap
b
c
solid
insulation
non-conductive non-conductive
wall wall
c
d
a d
conductive (metallic) wall
gap
bottom
IEC
Key
a
distance to conductive wall according Table 1, reduced distance
b
distance to non conductive wall with thickness t ; b ≥ (distance according Table 1) – t
c
distance to gap, minimum radius according Table 1, no reduced distance
d
creepage distance according Table 2
Figure 1 – Distances through filling material
Malfunction conditions according to 4.8 shall be considered when determining the working
voltage.
NOTE While this standard is applicable to equipment with a rated supply voltage not exceeding 1 000 V, Table 1
takes into account working voltages greater than 1 000 V which can be developed or generated within the
equipment or Ex Component. A typical example is a fluorescent luminaire ballast with a rated voltage of 240 V, but
with an arc initiation voltage of approximately 2 000 V.
4.3.2 Distances surrounding free space
If electrical equipment contains components which have an enclosed free space not filled with
the filling material (e.g. a relay), the following requirements apply:
– if the enclosed free space of the component is less than 3 cm , the minimum distance
through the filling material between the component wall and the inner surface of the
container shall comply with Table 1. The reduced distances are not permitted;
3 3
– if the enclosed free space of the component is between 3 cm and 30 cm , the minimum
distance through the filling material between the component wall and the inner surface of
the container shall comply with Table 1 but with a minimum of 15 mm;
– the component shall be fixed, so that movement nearer to the wall of the container is not
possible;
– the free volume shall not exceed 30 cm ;
– the enclosure of the component shall resist the thermal and mechanical stresses to which
it will be subjected even under malfunction conditions according to 4.8. There shall be no
damage or distortion which could reduce the protection provided by the filling material.

– 12 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
4.4 Connections
4.4.1 Equipment
Cables used for the entry of electrical conductors into a powder filled “q” container shall be an
integral part of the equipment and shall be protected and sealed as specified in 4.1.1. The
clamping means shall comply with the cable gland requirements of IEC 60079-0 and shall not
be capable of being removed without obvious damage to the powder filled “q” container.
4.4.2 Ex Components
Connection to powder filled “q” Ex Components shall comply with the connection facilities and
termination compartments requirements of IEC 60079-0.
4.5 Capacitors
The total stored energy of all capacitors in an enclosure of electrical equipment, part of
electrical equipment or Ex component protected by powder filling “q” shall not exceed 20 J in
normal operation.
4.6 Cells and batteries
Enclosures for powder filled “q” electrical equipment, parts of electrical equipment or Ex
components that contain cells or batteries shall incorporate a breathing device to the
surrounding atmosphere (see 4.1.3) unless the batteries or cells:
a) have a capacity of 1,5 Ah or less, or
b) do not release gas under normal operating conditions, and comply with the requirements
for primary and secondary batteries with a capacity up to 25 Ah, of IEC 60079-7, for level
of protection “eb”.
NOTE Sealed gas-tight cells do not release gas under normal operating conditions.
4.7 Temperature limitations under overload conditions
Each electrical equipment, part of electrical equipment or Ex component protected by powder
filling “q” shall be protected against overload prescribed in the relevant product standard
specified by the manufacturer so that the temperature class is not exceeded inside the filling
material at a depth of 5 mm from the wall of the container. If the reduced dimension of Table 1
has been applied and results in a distance less than 5 mm, the reduced distance shall be
used in place of the 5 mm shown. The effectiveness of the protection shall be confirmed by
the test of 5.1.4.
NOTE It is often difficult to limit the temperatures with only a fuse, and an internal thermal protective device is
often necessary to comply with the maximum temperature requirements of 5.1.4.
4.8 Temperature limitations under malfunction conditions
4.8.1 General
The container shall not be damaged and the temperature class shall not be exceeded even in
the case of malfunctions as detailed in 4.8. The effectiveness of the temperature protection
shall be confirmed by the test in 5.1.4.
4.8.2 Fuse
Unless the equipment supply is protected by a fuse rated at not more than 170 % of the
maximum normal current, the equipment shall be subjected to any single internal electrical
malfunction which may cause either an overvoltage or overcurrent, for example:
– short-circuit of any component;
– open circuit due to any component failure;

© IEC 2022
– malfunction in the printed circuitry.
Fuses, if employed, shall have a voltage rating not less than that of the circuit and shall have
a breaking capacity not less than the prospective fault current of the circuit.
If a malfunction can lead to one or more subsequent malfunctions, for example overloading of
a component, the primary and subsequent malfunctions are considered to be a single
malfunction.
Where there is no product standard, the overloads to be considered are those specified by the
manufacturer.
The voltage U shall be assumed to be applied to the supply terminals when considering
n
malfunction conditions and malfunction exclusions.
When the fuse is not integral to the electrical equipment or parts of electrical equipment, the
certificate number shall include the "X" suffix in accordance with the marking requirements of
IEC 60079-0 and the Specific Conditions of Use listed on the certificate shall detail the
required fuse.
When the fuse is not integral to an Ex component, the certificate number shall include the
symbol "U" in accordance with IEC 60079-0 and the schedule of limitations shall detail the
required fuse.
4.8.3 Malfunction exclusions
The following malfunctions need not be considered.
a) Resistance values lower than the rated values for:
– film type resistors,
– wire wound resistors and coils with a single layer in helical form,
when they are used at no more than 2/3 of their rated voltage and rated power at the
maximum service temperature as specified by the manufacturer of the respective
components.
b) Short-circuit conditions for:
– plastic foil capacitors,
– ceramic capacitors,
– paper capacitors,
when they are used at no more than 2/3 of their rated voltage as specified by the
manufacturer of the respective components.
c) Insulation failure of:
– galvanically separating components (e.g. optocouplers and relays) designed for
segregation of different circuits,
when the sum U of the r.m.s. values of the maximum voltages of the two circuits is not
more than 1 000 V and the rated voltage of the component between the two different
circuits is at least 1,5 times U.
NOTE Galvanically separating components providing double or reinforced insulation according to a product
standard are considered to meet the requirements of IEC 61140, e.g. IEC 60747-5-5 for photo coupler.
d) Transformers, coils and windings, which:
– comply with Level of Protection “eb” in IEC 60079-7, or
– comply with the requirements for mains transformers, Level of Protection “ia” or “ib”, in
IEC 60079-11, or
– comply with IEC 61558-2-6, or

– 14 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
– provide a double or reinforced insulation between the circuit per IEC 61558-1.
It is not necessary to consider the possibility of a short circuit if the distances or creepage
distances between bare live parts or printed tracks are at least equal to the values of Table 2
(for methods of measuring creepage distances see IEC 60079-7 and IEC 60079-11).
The maximum voltage between the parts shall be used to determine the distances according
to Table 2. If the parts are electrically isolated, the sum of the maximum voltages of the two
circuits shall be considered as the voltage. The maximum voltage shall be assessed taking
into account normal operating conditions (transients being disregarded) and malfunction
conditions as specified in this standard.
For distance under a coating according to Table 2, the following conditions apply:
– a conformal coating shall have the effect of sealing the conductors in question against
ingress of moisture;
– it shall adhere to the conductive parts and to the insulation material;
– if the conformal coating is applied by spraying, then two separate coats are to be applied;
– other methods of application require only one coat, for example, dip coating, brushing,
vacuum impregnating, but the intention is to achieve an effective, lasting, unbroken seal;
– a solder mask is considered as one of the two coatings, provided it is not damaged during
soldering.
Conductive parts protruding from the insulation (including soldered component pins) shall not
be considered as coated unless special measures have been applied to obtain an effective
unbroken seal.
Where bare parts of energized circuits emerge from the coating, the comparative tracking
index (CTI) in Table 2 applies to both insulation and conformal coating.

© IEC 2022
Table 2 – Creepage distances and distances through filling material
a
Voltage Creepage Minimum Distance under Distance through
b
a.c. or d.c. distance value coating filling material
U
r.m.s.
V mm CTI mm mm
c
U ≤ 10 1,6 0,6 1,5
–
U≤ 12,5 1,6 100 0,6 1,5
1,6 100 0,6 1,5
U ≤ 16
1,6 100 0,6 1,5
U≤ 20
U ≤ 25 1,7 100 0,6 1,5
U ≤ 32 1,8 100 0,7 1,5
3 100 0,7 1,5
U ≤ 40
U ≤ 50 3,4 100 0,7 1,5
U ≤ 63 3,4 100 1 1,5
3,6 100 1 1,5
U ≤ 80
3,8 100 1,3 2
U ≤ 100
U ≤ 125 4 175 1,3 2
U ≤ 160 5 175 1,3 2
6,3 175 2,6 3
U ≤ 200
U ≤ 250 8 175 2,6 3
U ≤ 320 10 175 2,6 3
12,5 175 3,3 3
U ≤ 400
U ≤ 500 16 175 5 3
U≤ 630 20 175 6 5
25 175 6 5
U ≤ 800
32 175 8,3 5
U ≤ 1 000
U ≤ 1 250 32 175 12 10
32 175 13,3 10
U ≤ 1 600
32 175 13,3 10
U ≤ 2 000
U≤ 2 500 40 175 13,3 10
U ≤ 3 200 50 175 16 14
63 175 21 14
U ≤ 4 000
U ≤ 5 000 80 175 27 14
U ≤ 6 300 100 175 33 25
125 175 41 25
U≤ 8 000
160 175 55 40
U≤ 10 000
a
When determining the required values for creepage and distance, the working voltage may be higher than
the voltage in the table by a factor of 1,1 (see Note).
NOTE The factor of 1,1 recognizes that at many places in a circuit, the working voltage equals the rated
voltage and that there are a number of rated voltages in common use that can be accommodated by the 1,1
factor.
b
If material with higher CTI value is used, the use of the Level of Protection “eb” creepage distances given for
that CTI in IEC 60079-7 is permitted.
c
At 10 V and below, the value of CTI is not relevant.

– 16 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
4.8.4 Protective devices for temperature limitation
Temperature limitation may be achieved by an internal or external, electrical or thermal,
protective device. The device shall not be self-resetting.
Where integral fuses are used as protective devices, the fusing element shall be of the
enclosed type, for example, in glass or ceramic.
Over-current devices shall have a voltage rating not less than that of the circuit and shall have
a breaking capacity not less than the prospective fault current of the circuit.
4.8.5 Power supply prospective short-circuit current
Electrical equipment, parts of electrical equipment and Ex components protected by powder
filling “q”, with a rated voltage of not greater than 250 V a.c., shall be suitable for operation
from a supply system with a prospective short-circuit current of 1 500 A unless the marking
includes the value of the permitted prospective short-circuit current. Higher prospective
currents than 1 500 A could be present in some installations, for example at higher voltages.
If a current limiting device is necessary to limit the prospective short-circuit current to a value
not greater than the rated breaking capacity of the fuse, this device shall be a resistor
according to 4.8.3 a) and the rated values shall be:
– current rating 1,5 × 1,7 × I of the fuse;
n
– externally applied maximum voltage U ;
m
– power rating 1,5 × (1,7 × I of the fuse) × resistance of limiting device.
n
If the manufacturer does not provide a required short-circuit protective device, the certificate
number for the electrical equipment or parts of electrical equipment shall include the "X" suffix
in accordance with the marking requirements of IEC 60079-0 and the Specific Conditions of
Use listed on the certificate shall detail the short-circuit protective devices required.
5 Verifications and tests
5.1 Type verifications and tests
5.1.1 Pressure type test of container
The pressure tests shall be conducted on the samples subjected to the tests of enclosures in
IEC 60079-0. Irrespective of its volume, the container samples shall be subjected to a
pressure type test with an over-pressure of 50 kPa without the occurrence of permanent
deformation exceeding 0,5 mm in any of its dimensions. The pressure shall be applied for at
least 10 s.
For containers without breathing or degassing openings, which contain capacitors other than
plastic foil, paper or ceramic type and where the volume of the filling material is lower than
eight times the volume of the capacitors, the pressure type test with an overpressure of
1,5 MPa shall be applied for at least 10 s.
Where the reduced distances have been applied (4.3.1), the pressure test shall be conducted
hydraulically. There shall be no drops of water to blotting paper placed under the sample from
any of the joints of the sample not identified as a “gap” for the purposes of employing the
reduced distances.
NOTE 1 The test samples used for this test normally have the “gaps” sealed to allow the evaluation of the joints
without the drops of water expected to come from the “gaps”.
Tests may be conducted without the filling material present.

© IEC 2022
NOTE 2 When the container is also the external enclosure, the tests of enclosures requirements of IEC 60079-0
apply.
NOTE 3 The impact and drop tests of enclosures from IEC 60079-0 do not generally apply to Ex Components
intended to be mounted inside of another enclosure complying with IEC 60079-0, as the external enclosure
provides the protection against impact and drop.
5.1.2 Verification of the degree of protection of the enclosure
The degree of protection of the enclosure shall be verified in accordance with the method
specified in IEC 60529. Any breathing devices shall be in place. This test shall be carried out
after the pressure type test in 5.1.1 on any one of the samples.
NOTE 1 When the container is also the external enclosure, the tests of enclosures requirements of IEC 60079-0
apply.
NOTE 2 The impact and drop tests of enclosures from IEC 60079-0 do not generally apply to Ex Components
intended to be mounted inside of another enclosure complying with IEC 60079-0, as the external enclosure
provides the protection against impact and drop.
5.1.3 Dielectric strength Insulation resistance test of the filling material
The insulating properties of the filling material shall be tested prior to the filling process using
a sample of the filling material. For this purpose, the electrode arrangement shown in Figure 2
shall be used. The electrodes shall be covered by the filling material in all directions with a
thickness of at least 10 mm.
The sample shall be conditioned for at least 24 h at a temperature of (23 ± 2) °C and relative
+5
humidity of between 45 % and 55 %. A test voltage of 1 000 V d.c. % shall then be applied
to the electrodes.
The filling material complies with the requirements if the leakage current does not exceed
-6
10 A. If the material fails to comply, further conditioning and retesting are not permitted.
5.1.4 Maximum temperatures
Where current dependent fuses in accordance with IEC 60127 are used as protective devices
for temperature limitation, the maximum temperature under overload conditions shall be
measured with a continuous current of at least 1,7 times the fuse rating. If other fuses are
employed, the test current shall be based on the non-fusing current rating of the fuse.
Where items other than current dependent fuses are used as protective devices for
temperature limitation, the equipment shall be tested to verify that the temperature class is
not exceeded when those protective devices operate.
When required by 4.8.3 to consider a malfunction, any malfunction which could increase heat
dissipation but not cause a current dependant fuse to disconnect immediately shall be
considered. (Malfunctions that will cause immediate ruptu
...

IEC 60079-5 ®
Edition 4.0 2015-02
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 5: Equipment protection by powder filling “q”

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IEC 60079-5 ®
Edition 4.0 2015-02
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 5: Equipment protection by powder filling “q”

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.260.20 ISBN 978-2-8322-2270-6

– 2 – IEC 60079-5:2015 RLV © IEC 2015

CONTENTS
FOREWORD . 4
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Constructional requirements . 8
4.1 Enclosure Containers . 8
4.1.1 Closing and sealing . 8
4.1.2 Pressure test of container . 9
4.1.3 Degree of protection of the container . 9
4.1.4 Filling procedure . 10
4.1.5 Containers that are not external enclosures . 10
4.2 Filling material . 10
4.2.1 Material specification . 10
4.2.2 Documentation . 10
4.2.3 Testing . 10
4.3 Distances . 10
4.3.1 Distances through filling material . 10
4.3.2 Distances surrounding free space . 12
4.4 Materials used for support of energized parts Connections . 13
4.4.1 Equipment . 13
4.4.2 Ex Components . 13
4.5 External field-wiring connections .
4.5 Capacitors . 13
4.6 Cells and batteries . 13
4.7 Temperature limitations under overload conditions. 13
4.8 Temperature limitations under fault malfunction conditions . 14
4.8.1 General . 14
4.8.2 Fuse . 14
4.8.3 Malfunction exclusions . 14
4.8.4 Protective devices for temperature limitation. 17
4.8.5 Power supply prospective short-circuit current . 17
5 Verifications and tests . 17
5.1 Type verifications and tests . 17
5.1.1 Pressure type test of container . 17
5.1.2 Verification of the degree of protection of the enclosure . 18
5.1.3 Dielectric strength test of the filling material . 18
5.1.4 Maximum temperatures . 18
5.2 Routine verifications and tests . 19
5.2.1 Routine pressure test of container . 19
5.2.2 Dielectric strength test of the filling material . 20
6 Marking . 21
7 Instructions . 21

Annex A (informative) Introduction of an alternative risk assessment method
encompassing ‘equipment protection levels’ for Ex equipment .

Bibliography . 27

Figure 1 – Distances through filling material . 12
Figure 1 2 – Test arrangement for the dielectric strength test of the filling material . 20

Table 1 – Distances through the filling material . 11
Table 2 – Creepage distances and distances through filling material. 16
Table A.1 – Traditional relationship of EPLs to zones (no additional risk assessment) .
Table A.2 – Description of risk of ignition protection provided .

– 4 – IEC 60079-5:2015 RLV © IEC 2015

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 5: Equipment protection by powder filling “q”

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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Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
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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
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
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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.

This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.

International Standard IEC 60079-5 has been prepared by IEC technical committee 31:
Equipment for explosive atmospheres.
This fourth edition cancels and replaces the third edition, published in 2007, and constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
NOTE The technical changes referred to include the significant technical changes in the revised IEC standard, but
they do not form an exhaustive list of all modifications from the previous edition. More guidance may be found by
referring to the redline version of the IEC standard, if available.

Type
Significant changes Clause/subclause Minor and Extension Major
editorial technical
changes changes
Specific references to IEC 60079-0 have been
4.1.3 4.8 4.8.3 X
reworded so the references to IEC 60079-0 can
be non-dated references
The “housing” surrounding the powder filled
equipment or Ex Component has been
redefined as a “container” to avoid confusion 4.1 X
with the “enclosure” requirements of
IEC 60079-0
A relaxation has been introduced to permit
reduced distances through filling material for
4.3.1 X
instances where there is no adjacent gap in the
container
A relaxation has been introduced to permit the
use of creepage dimensions per IEC 60079-7 4.8.3 X
where CTI is better than 175
An evaluation of joints employed when the
5.1.1 X
reduced distances according to Table 1 are
applied, has been added.
Text for determination of maximum temperature
clarified with respect to overloads and 5.1.4 X
malfunctions
A batch routine test has been introduced 5.2.1 X

The text of this standard is based on the following documents:
FDIS Report on voting
31/1156/FDIS 31/1171/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.
The list of all parts of IEC 60079 series, under the general title Explosive atmospheres, can
be found on the IEC website.
– 6 – IEC 60079-5:2015 RLV © IEC 2015

The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website 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.
IMPORTANT – The “colour inside” logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this publication using a colour printer.

EXPLOSIVE ATMOSPHERES –
Part 5: Equipment protection by powder filling “q”

1 Scope
This part of IEC 60079 contains specific requirements for the construction, testing and
marking of electrical equipment, parts of electrical equipment and Ex components in the type
of protection powder filling “q”, intended for use in explosive gas atmospheres.
NOTE 1 Electrical equipment and Ex components protected by powder filling “q” may can contain electronic
circuits, transformers, protection fuses, relays, intrinsically safe electrical apparatus, associated electrical
apparatus, switches, etc.
NOTE 2 Type of protection powder filling “q” provides Equipment Protection Level (EPL) Gb or Mb. For further
information, see Annex A.
This standard supplements and modifies the general requirements of IEC 60079-0. Where a
requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of
this standard takes precedence.
This standard applies to electrical equipment, parts of electrical equipment and Ex
components with:
– a rated supply current less than or equal to 16 A;
– a rated supply voltage less than or equal to 1 000 V;
– a rated power consumption less than or equal to 1 000 W.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60079-0:2004, Explosive atmospheres – Part 0: Equipment – General requirements
IEC 60079-1, Electrical apparatus for explosive gas atmospheres – Part 1: Flameproof
enclosure “d”
IEC 60079-7, Explosive atmospheres – Part 7: Equipment protection by increased safety "e"
IEC 60079-11, Explosive atmospheres – Part 11: Equipment protection by intrinsic safety "i"
IEC 60127 (all parts), Miniature fuses
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 61558-1, Safety of power transformers, power supplies, reactors and similar products –
Part 1: General requirements and tests
IEC 61558-2-6, Safety of transformers, reactors, power supply units and similar products for
supply voltages up to 1 100 V – Part 2-6: Particular requirements and tests for safety isolating
transformers and power supply units incorporating safety isolating transformers

– 8 – IEC 60079-5:2015 RLV © IEC 2015

ISO 2859-1, Sampling procedures for inspection by attributes – Part 1: Sampling schemes
indexed by acceptance quality limit (AQL) for lot-by-lot inspection
ISO 3310-1, Test sieves – Technical requirements and testing – Part 1: Test sieves of metal
wire cloth
ISO 3310-2, Test sieves – Technical requirements and testing – Part 2: Test sieves of
perforated metal plates
ISO 2591-1, Test sieving – Methods using test sieves of woven wire cloth and perforated
metal plate
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60079-0 as well as
the following apply.
NOTE Additional definitions applicable to explosive atmospheres can be found in IEC 60050-426.
3.1
powder filling “q”
type of protection in which the parts capable of igniting an explosive gas atmosphere are fixed
in position and completely surrounded by filling material to prevent the ignition of an external
explosive gas atmosphere
Note 1 to entry: The type of protection may not prevent the surrounding explosive gas atmosphere from
penetrating into the equipment and components and being ignited by the circuits. However, due to the small free
volumes in the filling material and due to the quenching of a flame which may propagate through the paths in the
filling material, an external explosion is prevented.
3.2
filling material
solid quartz or solid glass particles
3.3
distance through filling material
shortest distance through a filling material between two conductive parts
container (for filling material)
housing immediately surrounding the electrical equipment protected by and containing the
filling material
Note 1 to entry: The container may, in some cases, also be the external enclosure.
4 Constructional requirements
4.1 Enclosure Containers
In addition to the enclosure requirements of IEC 60079-0, the following requirements apply.
4.1.1 Closing and sealing
4.1.1.1 General
Enclosures Containers of electrical equipment, parts of electrical equipment or Ex
components protected by powder filling ”q” shall be filled and sealed at the time of
manufacture. The closing and sealing shall be the methods of 4.1.1.2 or 4.1.1.3.

4.1.1.2 Enclosures Containers permanently sealed at the time of manufacture
The enclosure container shall be permanently sealed at the time of manufacture and shall not
be capable of being opened without leaving visible evidence that the enclosure container has
been opened. The enclosure container shall be marked in accordance with Clause 6, item a).
NOTE Suitable techniques that can provide visible evidence of containers being opened are, for example,
welding, soldering, cemented joints, rivets, cementing of screws, or lead-seal safety-wiring of screws.
4.1.1.3 Enclosures Containers intended to be opened for repair
Electrical equipment, parts of electrical equipment, or Ex components that are designed to be
repaired shall incorporate sealing methods that are capable of being renewed without damage
to the enclosure container when the equipment is repaired, re-filled, and re-sealed. The
enclosure container shall be marked in accordance with Clause 6, item b).
NOTE Suitable techniques that may provide visible evidence of being opened are, for example, welding,
soldering, cemented joints, rivets, cementing of screws, or lead-seal safety-wiring of screws.
4.1.2 Pressure test of enclosure container
The electrical equipment, parts of electrical equipment or Ex components protected by powder
filling “q” shall meet the pressure test requirements specified in 5.1.1.
4.1.3 Degree of protection of the enclosure container
The enclosure container of the electrical equipment, parts of electrical equipment, or Ex
components protected by powder filling “q”, in their normal service condition, i.e. with all
openings closed as in normal use, shall comply at least with the degree of protection IP54 as
defined in IEC 60529. If the degree of protection is IP55 or higher, and the enclosure
container is not hermetically sealed, the container shall be provided with a breathing device.
The enclosure container with the breathing device in place shall comply at least with the
degree of protection IP54 according to IEC 60529. The test shall be conducted on an empty
enclosure container without the powder filling installed. At the end of any water ingress tests,
no water shall be visible inside the enclosure container.
NOTE 1 As the enclosure container may need to be destroyed in order to determine the entrance of dust or
water, two separate test samples may could be required for the two ingress tests.
NOTE 2 When the container is also the external enclosure, the tests of enclosures requirements of IEC 60079-0
apply.
The ingress protection of enclosures containers or parts of electrical equipment protected by
powder filling “q”, intended for use only in clean, dry rooms, may be reduced to degree of
protection IP43. These enclosures The certificate number of this equipment shall include the
symbol "X" suffix in accordance with 29.2 i) the marking requirements of IEC 60079-0, and the
Specific Conditions of Use listed on the certificate shall detail the restrictions of use.
When Ex components protected by powder filling “q” are intended to be mounted inside
another enclosure complying with IEC 60079-0, this outer enclosure shall have a degree of
protection of at least IP54. The IP rating of the inner enclosure container does not need to be
specified provided that the Ex component is mounted in a position where it is unlikely to be
contaminated by any small amounts of water that may enter the outer enclosure.
NOTE 3 The impact and drop tests of enclosures from IEC 60079-0 do not generally apply to Ex Components
intended to be mounted inside another enclosure complying with IEC 60079-0, as the external enclosure provides
the protection against impact and drop.
The maximum gap of an enclosure a container protected by powder filling “q” shall be at least
0,1 mm smaller than the specified smallest dimension of the filling material.
NOTE 4 The restriction on the size of the gap is intended to reduce the escape of filling material.

– 10 – IEC 60079-5:2015 RLV © IEC 2015

4.1.4 Filling procedure
Filling shall be carried out so as not to leave any void within the filling material (for example
by shaking down). The free space within electrical equipment, parts of electrical equipment or
Ex components protected by powder filling “q” shall be effectively filled with filling material
(see also 4.3.2).
4.1.5 Containers that are not external enclosures
The container of type of protection “q” equipment or Ex Component that is installed or
intended to be installed internal to another enclosure is considered the same as that of an Ex
Component.
4.2 Filling material
4.2.1 Requirements Material specification
The material shall be quartz or solid glass particles.
The material specification shall be tested dry state that, determined in accordance with the
ISO 2591-1 procedure for dry materials, the size of particles are within the following sieve
sizes using a:
– 1 mm nominal aperture sieve in accordance with ISO 3310-1 or ISO 3310-2
– 500 µm nominal aperture sieve in accordance with ISO 3310-1.
4.2.2 Documentation
The documents prepared by the manufacturer in accordance with IEC 60079-0 shall include
the specification of the particle material, the size range of the particles, as well as the filling
process and the measures taken to ensure proper filling.
NOTE It is not a requirement of this standard that conformity to the specification of the particle material and size
range of the particles needs to be verified.
4.2.3 Testing
The filling material shall be subjected to the dielectric strength test specified in 5.1.3.
4.3 Distances
4.3.1 Distances through filling material
Except where specified otherwise in this standard, the minimum distance through the filling
material between electrically conducting parts of the equipment and the inner surface of the
enclosure container shall comply with Table 1 and Figure 1. This does not apply to conductors
used for external field wiring connections which penetrate the wall of the enclosure container.
Such conductors shall comply with any requirements for the type of protection employed for
the external connections.
Table 1 – Distances through the filling material
a b
Voltage a.c. r.m.s. or d.c. Minimum distance Reduced distance
V mm mm
5 1,5
U ≤ 80
U ≤ 100 5 2
5 2
U ≤125
U ≤ 160 5 2
5 3
U ≤ 200
5 3
U ≤ 250
6,3 3
U ≤ 400
U ≤ 500 8 3
U ≤ 800 10 5
14 5
U ≤ 1 000
U ≤ 1 600 16 10
U ≤ 2 500 25 10
32 10
U ≤ 3 200
40 14
U ≤ 4 000
U ≤ 5 000 50 14
63 25
U ≤ 6 300
80 25
U ≤ 8 000
U ≤ 10 000 100 40
NOTE Voltages shown are derived from IEC 60664-1 and are based on the rationalization of supply voltages
given in Table 3b. When determining the required values for distance, the voltage value in the table may be
increased by a factor of 1.1 in order to recognize the range of rated voltages in common use.

a
When determining the required values for creepage and distance, the working voltage may be higher than
the voltage in the table by a factor of 1,1 (see Note).
NOTE The factor of 1,1 recognizes that at many places in a circuit, the working voltage equals the rated
voltage and that there are a number of rated voltages in common use that can be accommodated by the 1,1
factor.
b
To ensure that there is a sufficient path length through the filling material to provide quenching of a flame
from the inside to the outside of the container, the reduced distances shown are permitted only when there
is no adjacent gap in the container that could permit a flame to exit. See Figure 1.

– 12 – IEC 60079-5:2015 RLV © IEC 2015

top
t t
conductive (metallic) wall
a
c
gap
gap
b
c
solid
insulation
non-conductive non-conductive
wall wall
c
d
a d
conductive (metallic) wall
gap
bottom
IEC
Key
a
distance to conductive wall according Table 1, reduced distance
b
distance to non conductive wall with thickness t ; b ≥ (distance according Table 1) – t
c
distance to gap, minimum radius according Table 1, no reduced distance
d
creepage distance according Table 2
Figure 1 – Distances through filling material
Fault Malfunction conditions according to 4.8 shall be considered when determining the
working voltage.
NOTE While this standard is applicable to equipment with a rated supply voltage not exceeding 1 000 V, Table 1
takes into account working voltages greater than 1 000 V which may can be developed or generated within the
equipment or Ex Component. A typical example is a fluorescent luminaire ballast with a rated voltage of 240 V, but
with an arc initiation voltage of approximately 2 000 V.
4.3.2 Distances surrounding free space
If electrical equipment contains components which have an enclosed free space not filled with
the filling material (e.g. a relay), the following requirements apply:
– if the enclosed free space of the component is less than 3 cm , the minimum distance
through the filling material between the component wall and the inner surface of the
enclosure container shall comply with Table 1. The reduced distances are not permitted;
3 3
– if the enclosed free space of the component is between 3 cm and 30 cm , the minimum
distance through the filling material between the component wall and the inner surface of
the enclosure container shall comply with Table 1 but with a minimum of 15 mm;
– the component shall be fixed, so that movement nearer to the wall of the enclosure
container is not possible;
– the free volumes of more than shall not exceed 30 cm are not permitted;
– the enclosure of the component shall resist the thermal and mechanical stresses to which
it will be subjected even under fault malfunction conditions according to 4.8. There shall
be no damage or distortion which could reduce the protection provided by the filling
material.
4.4 Materials used for support of energized parts
Materials used between the electrically energized parts and the wall of the enclosure (except
for the insulation of external wiring and the filling material) in the region specified in shall
comply with the flammability requirements specified in .
4.5 External field-wiring connections
Terminations or Cables used for the entry of electrical conductors into a powder filled “q”
enclosure shall be an integral part of the enclosure and shall be protected and sealed as
specified in 4.1.1. When a cable provides the entry of conductors into a powder filled “q”
equipment or Ex component, The clamping means shall comply with the cable gland
requirements of IEC 60079-0 and shall not be capable of being removed without obvious
damage to the powder filled “q” enclosure.
4.4 Connections
4.4.1 Equipment
Cables used for the entry of electrical conductors into a powder filled “q” container shall be an
integral part of the equipment and shall be protected and sealed as specified in 4.1.1. The
clamping means shall comply with the cable gland requirements of IEC 60079-0 and shall not
be capable of being removed without obvious damage to the powder filled “q” container.
4.4.2 Ex Components
Connection to powder filled “q” Ex Components shall comply with the connection facilities and
termination compartments requirements of IEC 60079-0.
4.5 Capacitors
The total stored energy of all capacitors in an enclosure of electrical equipment, part of
electrical equipment or Ex component protected by powder filling “q” shall not exceed 20 J in
normal operation.
4.6 Cells and batteries
Enclosures for powder filled “q” electrical equipment, parts of electrical equipment or Ex
components that contain cells or batteries shall incorporate a breathing device to the
surrounding atmosphere (see 4.1.3) unless the batteries or cells:
a) have a capacity of 1,5 Ah or less, or
b) do not release gas under normal operating conditions, and comply with the requirements
for primary and secondary batteries with a capacity up to 25 Ah, of IEC 60079-7, for level
of protection “eb”.
NOTE Sealed gas-tight cells do not release gas under normal operating conditions.
NOTE 2 Consideration shall be given to the effect that a release from the breather may have on the surrounding
atmosphere.
4.7 Temperature limitations under overload conditions
Each electrical equipment, part of electrical equipment or Ex component protected by powder
filling “q” shall be protected against overload prescribed in the relevant product standard
specified by the manufacturer so that the permissible limit temperature of the applicable
temperature class is not exceeded at the wall of the enclosure and inside the filling material
up to at a depth of 5 mm from the wall of the enclosure container. If the reduced dimension of
Table 1 has been applied and results in a distance less than 5 mm, the reduced distance shall
be used in place of the 5 mm shown. The effectiveness of the protection shall be confirmed by
the test of 5.1.4.
– 14 – IEC 60079-5:2015 RLV © IEC 2015

NOTE It is often difficult to limit the temperatures with only a fuse, and an internal thermal protective device may
be is often necessary to comply with the maximum temperature requirements of 5.1.4.
4.8 Temperature limitations under fault malfunction conditions
4.8.1 General
The enclosure container shall not be damaged and the limiting temperature class shall not be
exceeded even in the case of faults malfunctions as detailed in 4.8. The effectiveness of the
temperature protection shall be confirmed by the test in 5.1.4.
4.8.2 Fuse
Unless the equipment supply is protected by a fuse rated at not more than 170 % of the
maximum normal current, the equipment shall be subjected to any single internal electrical
fault malfunction which may cause either an overvoltage or overcurrent, for example:
– short-circuit of any component;
– open circuit due to any component failure;
– fault malfunction in the printed circuitry.
Over-current devices Fuses, if employed, shall have a voltage rating not less than that of the
circuit and shall have a breaking capacity not less than the prospective fault current of the
circuit.
If a fault malfunction can lead to one or more subsequent faults malfunctions, for example
overloading of a component, the primary and subsequent faults malfunctions are considered
to be a single fault malfunction.
Where there is no product standard, the overloads to be considered are those specified by the
manufacturer.
The voltage U shall be assumed to be applied to the supply terminals when considering fault
n
malfunction conditions and fault malfunction exclusions.
When the fuse is not integral to the electrical equipment or parts of electrical equipment, the
marking certificate number shall include the symbol "X" suffix in accordance with 29.2 i) the
marking requirements of IEC 60079-0 and the Specific Conditions of Use listed on the
certificate shall detail the required fuse.
When the fuse is not integral to an Ex component, the marking certificate number shall
include the symbol "U" in accordance with 29.5 g) of IEC 60079-0 and the schedule of
limitations shall detail the required fuse.
4.8.3 Fault Malfunction exclusions
The following faults malfunctions need not be considered.
a) Resistance values lower than the rated values for:
– film type resistors,
– wire wound resistors and coils with a single layer in helical form,
when they are used at no more than 2/3 of their rated voltage and rated power at the
maximum service temperature as specified by the manufacturer of the respective
components.
b) Short-circuit conditions for:
– plastic foil capacitors,
– ceramic capacitors,
– paper capacitors,
when they are used at no more than 2/3 of their rated voltage as specified by the
manufacturer of the respective components.
c) Insulation failure of:
– galvanically separating components (e.g. optocouplers and relays) designed for
segregation of different circuits,
when the sum U of the r.m.s. values of the maximum voltages of the two circuits is not
more than 1 000 V and the rated voltage of the component between the two different
circuits is at least 1,5 times U.
NOTE Galvanically separating components providing double or reinforced insulation according to a product
standard are considered to meet the requirements of IEC 61140, e.g. IEC 60747-5-5 for photo coupler.
d) Transformers, coils and windings, which:
– comply with Level of Protection “eb” in IEC 60079-7, or transformers which
– comply with the requirements for mains transformers, Level of Protection “ia” or “ib”, in
IEC 60079-11, or
– comply with IEC 61558-2-6, or
– provide a double or reinforced insulation between the circuit per IEC 61558-1.
It is not necessary to consider the possibility of a short circuit if the distances or creepage
distances between bare live parts or printed tracks are at least equal to the values of Table 2
(for methods of measuring creepage distances see IEC 60079-7 and IEC 60079-11).
The maximum voltage between the parts shall be used to determine the distances according
to Table 2. If the parts are electrically isolated, the sum of the maximum peak voltages of the
two circuits shall be considered as peak the voltage. The maximum peak voltage shall be
assessed taking into account normal operating conditions (transients being disregarded) and
fault malfunction conditions as specified in this standard.
For distance under a coating according to Table 2, the following conditions apply:
– a conformal coating shall have the effect of sealing the conductors in question against
ingress of moisture;
– it shall adhere to the conductive parts and to the insulation material;
– if the conformal coating is applied by spraying, then two separate coats are to be applied;
– other methods of application require only one coat, for example, dip coating, brushing,
vacuum impregnating, but the intention is to achieve an effective, lasting, unbroken seal;
– a solder mask is considered as one of the two coatings, provided it is not damaged during
soldering.
Conductive parts protruding from the insulation (including soldered component pins) shall not
be considered as coated unless special measures have been applied to obtain an effective
unbroken seal.
Where bare parts of energized circuits emerge from the coating, the comparative tracking
index (CTI) in Table 2 applies to both insulation and conformal coating.

– 16 – IEC 60079-5:2015 RLV © IEC 2015

Table 1 – Creepage distances and distances through filling material
a
Voltage Creepage Minimum Distance under Distance through
b
a.c. or d.c. distance value coating filling material
U
r.m.s.
See Note
V mm CTI mm mm
c
1,6 0,6 1,5
U ≤ 10
–
1,6 175 100 0,6 1,5
U ≤ 12,5
1,6 175 100 0,6 1,5
U ≤ 16
U≤ 20 1,6 175 100 0,6 1,5
1,7 175 100 0,6 1,5
U ≤ 25
1,8 175 100 0,7 1,5
U ≤ 32
U ≤ 40 3 175 100 0,7 1,5
U ≤ 50 3,4 175 100 0,7 1,5
3,4 175 100 1 1,5
U ≤ 63
U ≤ 80 3,6 175 100 1 1,5
U ≤ 100 3,8 175 100 1,3 2
4 175 1,3 2
U ≤ 125
5 175 1,3 2
U ≤ 160
U ≤ 200 6,3 175 2,6 3
U ≤ 250 8 175 2,6 3
10 175 2,6 3
U ≤ 320
U ≤ 400 12,5 175 3,3 3
U ≤ 500 16 175 5 3
20 175 6 5
U≤ 630
U ≤ 800 25 175 6 5
U ≤ 1 000 32 175 8,3 5
32 175 12 10
U ≤ 1 250
32 175 13,3 10
U ≤ 1 600
U ≤ 2 000 32 175 13,3 10
40 175 13,3 10
U≤ 2 500
50 175 16 14
U ≤ 3 200
U ≤ 4 000 63 175 21 14
U ≤ 5 000 80 175 27 14
100 175 33 25
U ≤ 6 300
U≤ 8 000 125 175 41 25
U ≤ 10 000 160 175 55 40
NOTE Voltages shown are derived from IEC 60664-1 and is based on the rationalization of supply voltages
given in Table 3b. When determining the required values for creepage and clearance, the voltage value in the
table may be increased by a factor of 1.1 in order to recognize the range of rated voltages in common use.
a
When determining the required values for creepage and distance, the working voltage may be higher than
the voltage in the table by a factor of 1,1 (see Note).
NOTE The factor of 1,1 recognizes that at many places in a circuit, the working voltage equals the rated
voltage and that there are a number of rated voltages in common use that can be accommodated by the 1,1
factor.
b
If material with higher CTI value is used, the use of the Level of Protection “eb” creepage distances given for
that CTI in IEC 60079-7 is permitted.
c
NOTE At 10 V and below, the value of CTI is not relevant.

4.8.4 Protective devices for temperature limitation
Temperature limitation may be achieved by an internal or external, electrical or thermal,
protective device. The device shall not be self-resetting.
Where integral fuses are used as protective devices, the fusing element shall be of the
enclosed type, for example, in glass or ceramic.
Over-current devices shall have a voltage rating not less than that of the circuit and shall have
a breaking capacity not less than the prospective fault current of the circuit.
4.8.5 Power supply prospective short-circuit current
Electrical equipment, parts of electrical equipment and Ex components protected by powder
filling “q” and designed to be connected to an external source of supply not exceeding with a
rated voltage of not greater than 250 V a.c., shall be suitable for operation from a supply
system with a prospective short-circuit current of 1 500 A unless the marking includes the
value of the permitted prospective short-circuit current. Higher prospective currents than 1
500 A could be present in some installations, for example at higher voltages.
If a current limiting device is necessary to limit the prospective short-circuit current to a value
not greater than the rated breaking capacity of the fuse, this device shall be a resistor
according to 4.8.3 a) and the rated values shall be:
of the fuse;
– current rating 1,5 × 1,7 × I
n
– externally applied maximum voltage U ;
m
– power rating 1,5 × (1,7 × I of the fuse) × resistance of limiting device.
n
If the manufacturer does not provide a required short-circuit protective device, the certificate
number for the electrical equipment or parts of electrical equipment shall include the symbol
"X" suffix in accordance with 29.2 i) the marking requirements of IEC 60079-0 and the
Specific Conditions of Use listed on the certificate shall detail the short-circuit protective
devices required.
5 Verifications and tests
5.1 Type verifications and tests
5.1.1 Pressure type test of enclosure container
The pressure tests shall be conducted on the samples subjected to the tests of enclosures in
IEC 60079-0. Irrespective of its volume, the enclosure container samples shall be subjected to
a pressure type test with an over-pressure of 50 kPa without the occurrence of permanent
deformation exceeding 0,5 mm in any of its dimensions. The pressure shall be applied for at
least 10 s.
...

IEC 60079-5 ®
Edition 4.0 2015-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 5: Equipment protection by powder filling “q”

Atmosphères explosives –
Partie 5: Protection du matériel par remplissage pulvérulent “q”

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IEC 60079-5 ®
Edition 4.0 2015-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 5: Equipment protection by powder filling “q”

Atmosphères explosives –
Partie 5: Protection du matériel par remplissage pulvérulent “q”

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-2249-2

– 2 – IEC 60079-5:2015 © IEC 2015
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references. 6
3 Terms and definitions . 7
4 Constructional requirements . 7
4.1 Containers . 7
4.1.1 Closing and sealing . 7
4.1.2 Pressure test of container . 8
4.1.3 Degree of protection of the container . 8
4.1.4 Filling procedure . 8
4.1.5 Containers that are not external enclosures . 8
4.2 Filling material . 9
4.2.1 Material specification . 9
4.2.2 Documentation . 9
4.2.3 Testing . 9
4.3 Distances . 9
4.3.1 Distances through filling material . 9
4.3.2 Distances surrounding free space . 11
4.4 Connections . 12
4.4.1 Equipment . 12
4.4.2 Ex Components . 12
4.5 Capacitors . 12
4.6 Cells and batteries . 12
4.7 Temperature limitations under overload conditions . 12
4.8 Temperature limitations under malfunction conditions . 12
4.8.1 General . 12
4.8.2 Fuse . 12
4.8.3 Malfunction exclusions . 13
4.8.4 Protective devices for temperature limitation . 16
4.8.5 Power supply prospective short-circuit current . 16
5 Verifications and tests . 16
5.1 Type verifications and tests . 16
5.1.1 Pressure type test of container . 16
5.1.2 Verification of the degree of protection of the enclosure . 17
5.1.3 Dielectric strength test of the filling material . 17
5.1.4 Maximum temperatures . 17
5.2 Routine verifications and tests . 18
5.2.1 Routine pressure test of container . 18
5.2.2 Dielectric strength test of the filling material . 18
6 Marking . 19
7 Instructions. 20
Bibliography . 21

Figure 1 – Distances through filling material . 11
Figure 2 – Test arrangement for the dielectric strength test of the filling material . 19

Table 1 – Distances through the filling material. 10
Table 2 – Creepage distances and distances through filling material . 15

– 4 – IEC 60079-5:2015 © IEC 2015
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 5: Equipment protection by powder filling “q”

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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International Standard IEC 60079-5 has been prepared by IEC technical committee 31:
Equipment for explosive atmospheres.
This fourth edition cancels and replaces the third edition, published in 2007, and constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
NOTE The technical changes referred to include the significant technical changes in the revised IEC standard, but
they do not form an exhaustive list of all modifications from the previous edition. More guidance may be found by
referring to the redline version of the IEC standard, if available.

Type
Significant changes Clause/subclause Minor and Extension Major
editorial technical
changes changes
Specific references to IEC 60079-0 have been
4.1.3 4.8 4.8.3 X
reworded so the references to IEC 60079-0 can
be non-dated references
The “housing” surrounding the powder filled
equipment or Ex Component has been
redefined as a “container” to avoid confusion 4.1 X
with the “enclosure” requirements of
IEC 60079-0
A relaxation has been introduced to permit
reduced distances through filling material for
4.3.1 X
instances where there is no adjacent gap in the
container
A relaxation has been introduced to permit the
use of creepage dimensions per IEC 60079-7 4.8.3 X
where CTI is better than 175
An evaluation of joints employed when the
5.1.1 X
reduced distances according to Table 1 are
applied, has been added.
Text for determination of maximum temperature
clarified with respect to overloads and 5.1.4 X
malfunctions
A batch routine test has been introduced 5.2.1 X

The text of this standard is based on the following documents:
FDIS Report on voting
31/1156/FDIS 31/1171/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.
The list of all parts of 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 website 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.
– 6 – IEC 60079-5:2015 © IEC 2015
EXPLOSIVE ATMOSPHERES –
Part 5: Equipment protection by powder filling “q”

1 Scope
This part of IEC 60079 contains specific requirements for the construction, testing and
marking of electrical equipment, parts of electrical equipment and Ex components in the type
of protection powder filling “q”, intended for use in explosive gas atmospheres.
NOTE 1 Electrical equipment and Ex components protected by powder filling “q” can contain electronic circuits,
transformers, protection fuses, relays, intrinsically safe electrical apparatus, associated electrical apparatus,
switches, etc.
NOTE 2 Type of protection powder filling “q” provides Equipment Protection Level (EPL) Gb or Mb.
This standard supplements and modifies the general requirements of IEC 60079-0. Where a
requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of
this standard takes precedence.
This standard applies to electrical equipment, parts of electrical equipment and Ex
components with:
– a rated supply current less than or equal to 16 A;
– a rated supply voltage less than or equal to 1 000 V;
– a rated power consumption less than or equal to 1 000 W.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60079-0, Explosive atmospheres – Part 0: Equipment – General requirements
IEC 60079-7, Explosive atmospheres – Part 7: Equipment protection by increased safety "e"
IEC 60079-11, Explosive atmospheres – Part 11: Equipment protection by intrinsic safety "i"
IEC 60127 (all parts), Miniature fuses
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 61558-1, Safety of power transformers, power supplies, reactors and similar products –
Part 1: General requirements and tests
IEC 61558-2-6, Safety of transformers, reactors, power supply units and similar products for
supply voltages up to 1 100 V – Part 2-6: Particular requirements and tests for safety isolating
transformers and power supply units incorporating safety isolating transformers
ISO 2859-1, Sampling procedures for inspection by attributes – Part 1: Sampling schemes
indexed by acceptance quality limit (AQL) for lot-by-lot inspection

ISO 3310-1, Test sieves – Technical requirements and testing – Part 1: Test sieves of metal
wire cloth
ISO 3310-2, Test sieves – Technical requirements and testing – Part 2: Test sieves of
perforated metal plate
ISO 2591-1, Test sieving – Methods using test sieves of woven wire cloth and perforated
metal plate
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60079-0 as well as
the following apply.
NOTE Additional definitions applicable to explosive atmospheres can be found in IEC 60050-426.
3.1
powder filling “q”
type of protection in which the parts capable of igniting an explosive gas atmosphere are fixed
in position and completely surrounded by filling material to prevent the ignition of an external
explosive gas atmosphere
Note 1 to entry: The type of protection may not prevent the surrounding explosive gas atmosphere from
penetrating into the equipment and components and being ignited by the circuits. However, due to the small free
volumes in the filling material and due to the quenching of a flame which may propagate through the paths in the
filling material, an external explosion is prevented.
3.2
filling material
solid quartz or solid glass particles
3.3
container (for filling material)
housing immediately surrounding the electrical equipment protected by and containing the
filling material
Note 1 to entry: The container may, in some cases, also be the external enclosure.
4 Constructional requirements
4.1 Containers
4.1.1 Closing and sealing
4.1.1.1 General
Containers of electrical equipment, parts of electrical equipment or Ex components protected
by powder filling ”q” shall be filled and sealed at the time of manufacture. The closing and
sealing shall be the methods of 4.1.1.2 or 4.1.1.3.
4.1.1.2 Containers permanently sealed at the time of manufacture
The container shall be permanently sealed at the time of manufacture and shall not be
capable of being opened without leaving visible evidence that the container has been opened.
The container shall be marked in accordance with Clause 6, item a).
NOTE Suitable techniques that can provide visible evidence of containers being opened are, for example,
welding, soldering, cemented joints, rivets, cementing of screws, or lead-seal safety-wiring of screws.

– 8 – IEC 60079-5:2015 © IEC 2015
4.1.1.3 Containers intended to be opened for repair
Electrical equipment, parts of electrical equipment, or Ex components that are designed to be
repaired shall incorporate sealing methods that are capable of being renewed without damage
to the container when the equipment is repaired, re-filled, and re-sealed. The container shall
be marked in accordance with Clause 6, item b).
4.1.2 Pressure test of container
The electrical equipment, parts of electrical equipment or Ex components protected by powder
filling “q” shall meet the pressure test requirements specified in 5.1.1.
4.1.3 Degree of protection of the container
The container of the electrical equipment, parts of electrical equipment, or Ex components
protected by powder filling “q”, in their normal service condition, i.e. with all openings closed
as in normal use, shall comply at least with the degree of protection IP54 as defined in
IEC 60529. If the degree of protection is IP55 or higher, and the container is not hermetically
sealed, the container shall be provided with a breathing device. The container with the
breathing device in place shall comply at least with the degree of protection IP54 according to
IEC 60529. The test shall be conducted on an empty container without the powder filling
installed. At the end of any water ingress tests, no water shall be visible inside the container.
NOTE 1 As the container may need to be destroyed in order to determine the entrance of dust or water, two
separate test samples could be required for the two ingress tests.
NOTE 2 When the container is also the external enclosure, the tests of enclosures requirements of IEC 60079-0
apply.
The ingress protection of containers or parts of electrical equipment protected by powder
filling “q”, intended for use only in clean, dry rooms, may be reduced to degree of protection
IP43. The certificate number of this equipment shall include the "X" suffix in accordance with
the marking requirements of IEC 60079-0, and the Specific Conditions of Use listed on the
certificate shall detail the restrictions of use.
When Ex components protected by powder filling “q” are intended to be mounted inside
another enclosure complying with IEC 60079-0, this outer enclosure shall have a degree of
protection of at least IP54. The IP rating of the inner container does not need to be specified
provided that the Ex component is mounted in a position where it is unlikely to be
contaminated by any small amounts of water that may enter the outer enclosure.
NOTE 3 The impact and drop tests of enclosures from IEC 60079-0 do not generally apply to Ex Components
intended to be mounted inside another enclosure complying with IEC 60079-0, as the external enclosure provides
the protection against impact and drop.
The maximum gap of a container protected by powder filling “q” shall be at least 0,1 mm
smaller than the specified smallest dimension of the filling material.
NOTE 4 The restriction on the size of the gap is intended to reduce the escape of filling material.
4.1.4 Filling procedure
Filling shall be carried out so as not to leave any void within the filling material (for example
by shaking down). The free space within electrical equipment, parts of electrical equipment or
Ex components protected by powder filling “q” shall be effectively filled with filling material
(see also 4.3.2).
4.1.5 Containers that are not external enclosures
The container of type of protection “q” equipment or Ex Component that is installed or
intended to be installed internal to another enclosure is considered the same as that of an Ex
Component.
4.2 Filling material
4.2.1 Material specification
The material shall be quartz or solid glass particles.
The material specification shall state that, determined in accordance with the ISO 2591-1
procedure for dry materials, the size of particles are within the following sieve sizes:
– 1 mm nominal aperture sieve in accordance with ISO 3310-1 or ISO 3310-2
– 500 µm nominal aperture sieve in accordance with ISO 3310-1.
4.2.2 Documentation
The documents prepared by the manufacturer in accordance with IEC 60079-0 shall include
the specification of the particle material, the size range of the particles, as well as the filling
process and the measures taken to ensure proper filling.
NOTE It is not a requirement of this standard that conformity to the specification of the particle material and size
range of the particles needs to be verified.
4.2.3 Testing
The filling material shall be subjected to the dielectric strength test specified in 5.1.3.
4.3 Distances
4.3.1 Distances through filling material
Except where specified otherwise in this standard, the minimum distance through the filling
material between electrically conducting parts of the equipment and the container shall
comply with Table 1 and Figure 1. This does not apply to conductors used for field wiring
connections which penetrate the wall of the container.

– 10 – IEC 60079-5:2015 © IEC 2015
Table 1 – Distances through the filling material
a b
Voltage a.c. r.m.s. or d.c. Minimum distance Reduced distance
V mm mm
5 1,5
U ≤ 80
5 2
U ≤ 100
U ≤125 5 2
5 2
U ≤ 160
5 3
U ≤ 200
U ≤ 250 5 3
U ≤ 400 6,3 3
8 3
U ≤ 500
U ≤ 800 10 5
U ≤ 1 000 14 5
16 10
U ≤ 1 600
25 10
U ≤ 2 500
U ≤ 3 200 32 10
40 14
U ≤ 4 000
50 14
U ≤ 5 000
U ≤ 6 300 63 25
U ≤ 8 000 80 25
100 40
U ≤ 10 000
a
When determining the required values for creepage and distance, the working voltage may be higher than
the voltage in the table by a factor of 1,1 (see Note).
NOTE The factor of 1,1 recognizes that at many places in a circuit, the working voltage equals the rated
voltage and that there are a number of rated voltages in common use that can be accommodated by the 1,1
factor.
b
To ensure that there is a sufficient path length through the filling material to provide quenching of a flame
from the inside to the outside of the container, the reduced distances shown are permitted only when there
is no adjacent gap in the container that could permit a flame to exit. See Figure 1.

top
t
t
conductive (metallic) wall
a
c
gap
gap
b
c
solid
insulation
non-conductive non-conductive
wall wall
c
d
a d
conductive (metallic) wall
gap
bottom
IEC
Key
a
distance to conductive wall according Table 1, reduced distance
b
distance to non conductive wall with thickness t ; b ≥ (distance according Table 1) – t
c
distance to gap, minimum radius according Table 1, no reduced distance
d
creepage distance according Table 2
Figure 1 – Distances through filling material
Malfunction conditions according to 4.8 shall be considered when determining the working
voltage.
NOTE While this standard is applicable to equipment with a rated supply voltage not exceeding 1 000 V, Table 1
takes into account working voltages greater than 1 000 V which can be developed or generated within the
equipment or Ex Component. A typical example is a fluorescent luminaire ballast with a rated voltage of 240 V, but
with an arc initiation voltage of approximately 2 000 V.
4.3.2 Distances surrounding free space
If electrical equipment contains components which have an enclosed free space not filled with
the filling material (e.g. a relay), the following requirements apply:
– if the enclosed free space of the component is less than 3 cm , the minimum distance
through the filling material between the component wall and the inner surface of the
container shall comply with Table 1. The reduced distances are not permitted;
3 3
– if the enclosed free space of the component is between 3 cm and 30 cm , the minimum
distance through the filling material between the component wall and the inner surface of
the container shall comply with Table 1 but with a minimum of 15 mm;
– the component shall be fixed, so that movement nearer to the wall of the container is not
possible;
– the free volume shall not exceed 30 cm ;
– the enclosure of the component shall resist the thermal and mechanical stresses to which
it will be subjected even under malfunction conditions according to 4.8. There shall be no
damage or distortion which could reduce the protection provided by the filling material.

– 12 – IEC 60079-5:2015 © IEC 2015
4.4 Connections
4.4.1 Equipment
Cables used for the entry of electrical conductors into a powder filled “q” container shall be an
integral part of the equipment and shall be protected and sealed as specified in 4.1.1. The
clamping means shall comply with the cable gland requirements of IEC 60079-0 and shall not
be capable of being removed without obvious damage to the powder filled “q” container.
4.4.2 Ex Components
Connection to powder filled “q” Ex Components shall comply with the connection facilities and
termination compartments requirements of IEC 60079-0.
4.5 Capacitors
The total stored energy of all capacitors in an enclosure of electrical equipment, part of
electrical equipment or Ex component protected by powder filling “q” shall not exceed 20 J in
normal operation.
4.6 Cells and batteries
Enclosures for powder filled “q” electrical equipment, parts of electrical equipment or Ex
components that contain cells or batteries shall incorporate a breathing device to the
surrounding atmosphere (see 4.1.3) unless the batteries or cells:
a) have a capacity of 1,5 Ah or less, or
b) do not release gas under normal operating conditions, and comply with the requirements
for primary and secondary batteries with a capacity up to 25 Ah, of IEC 60079-7, for level
of protection “eb”.
NOTE Sealed gas-tight cells do not release gas under normal operating conditions.
4.7 Temperature limitations under overload conditions
Each electrical equipment, part of electrical equipment or Ex component protected by powder
filling “q” shall be protected against overload prescribed in the relevant product standard
specified by the manufacturer so that the temperature class is not exceeded inside the filling
material at a depth of 5 mm from the wall of the container. If the reduced dimension of Table 1
has been applied and results in a distance less than 5 mm, the reduced distance shall be
used in place of the 5 mm shown. The effectiveness of the protection shall be confirmed by
the test of 5.1.4.
NOTE It is often difficult to limit the temperatures with only a fuse, and an internal thermal protective device is
often necessary to comply with the maximum temperature requirements of 5.1.4.
4.8 Temperature limitations under malfunction conditions
4.8.1 General
The container shall not be damaged and the temperature class shall not be exceeded even in
the case of malfunctions as detailed in 4.8. The effectiveness of the temperature protection
shall be confirmed by the test in 5.1.4.
4.8.2 Fuse
Unless the equipment supply is protected by a fuse rated at not more than 170 % of the
maximum normal current, the equipment shall be subjected to any single internal electrical
malfunction which may cause either an overvoltage or overcurrent, for example:
– short-circuit of any component;
– open circuit due to any component failure;

– malfunction in the printed circuitry.
Fuses, if employed, shall have a voltage rating not less than that of the circuit and shall have
a breaking capacity not less than the prospective fault current of the circuit.
If a malfunction can lead to one or more subsequent malfunctions, for example overloading of
a component, the primary and subsequent malfunctions are considered to be a single
malfunction.
Where there is no product standard, the overloads to be considered are those specified by the
manufacturer.
The voltage U shall be assumed to be applied to the supply terminals when considering
n
malfunction conditions and malfunction exclusions.
When the fuse is not integral to the electrical equipment or parts of electrical equipment, the
certificate number shall include the "X" suffix in accordance with the marking requirements of
IEC 60079-0 and the Specific Conditions of Use listed on the certificate shall detail the
required fuse.
When the fuse is not integral to an Ex component, the certificate number shall include the
symbol "U" in accordance with IEC 60079-0 and the schedule of limitations shall detail the
required fuse.
4.8.3 Malfunction exclusions
The following malfunctions need not be considered.
a) Resistance values lower than the rated values for:
– film type resistors,
– wire wound resistors and coils with a single layer in helical form,
when they are used at no more than 2/3 of their rated voltage and rated power at the
maximum service temperature as specified by the manufacturer of the respective
components.
b) Short-circuit conditions for:
– plastic foil capacitors,
– ceramic capacitors,
– paper capacitors,
when they are used at no more than 2/3 of their rated voltage as specified by the
manufacturer of the respective components.
c) Insulation failure of:
– galvanically separating components (e.g. optocouplers and relays) designed for
segregation of different circuits,
when the sum U of the r.m.s. values of the maximum voltages of the two circuits is not
more than 1 000 V and the rated voltage of the component between the two different
circuits is at least 1,5 times U.
NOTE Galvanically separating components providing double or reinforced insulation according to a product
standard are considered to meet the requirements of IEC 61140, e.g. IEC 60747-5-5 for photo coupler.
d) Transformers, coils and windings, which:
– comply with Level of Protection “eb” in IEC 60079-7, or
– comply with the requirements for mains transformers, Level of Protection “ia” or “ib”, in
IEC 60079-11, or
– comply with IEC 61558-2-6, or

– 14 – IEC 60079-5:2015 © IEC 2015
– provide a double or reinforced insulation between the circuit per IEC 61558-1.
It is not necessary to consider the possibility of a short circuit if the distances or creepage
distances between bare live parts or printed tracks are at least equal to the values of Table 2
(for methods of measuring creepage distances see IEC 60079-7 and IEC 60079-11).
The maximum voltage between the parts shall be used to determine the distances according
to Table 2. If the parts are electrically isolated, the sum of the maximum voltages of the two
circuits shall be considered as the voltage. The maximum voltage shall be assessed taking
into account normal operating conditions (transients being disregarded) and malfunction
conditions as specified in this standard.
For distance under a coating according to Table 2, the following conditions apply:
– a conformal coating shall have the effect of sealing the conductors in question against
ingress of moisture;
– it shall adhere to the conductive parts and to the insulation material;
– if the conformal coating is applied by spraying, then two separate coats are to be applied;
– other methods of application require only one coat, for example, dip coating, brushing,
vacuum impregnating, but the intention is to achieve an effective, lasting, unbroken seal;
– a solder mask is considered as one of the two coatings, provided it is not damaged during
soldering.
Conductive parts protruding from the insulation (including soldered component pins) shall not
be considered as coated unless special measures have been applied to obtain an effective
unbroken seal.
Where bare parts of energized circuits emerge from the coating, the comparative tracking
index (CTI) in Table 2 applies to both insulation and conformal coating.

Table 2 – Creepage distances and distances through filling material
a
Voltage Creepage Minimum Distance under Distance through
b
a.c. or d.c. distance value coating filling material
U
r.m.s.
V mm CTI mm mm
c
U  10 1,6 0,6 1,5
–
U 12,5 1,6 100 0,6 1,5
U  16 1,6 100 0,6 1,5
1,6 100 0,6 1,5
U 20
1,7 100 0,6 1,5
U  25
U  32 1,8 100 0,7 1,5
U  40 3 100 0,7 1,5
3,4 100 0,7 1,5
U  50
U  63 3,4 100 1 1,5
U  80 3,6 100 1 1,5
3,8 100 1,3 2
U  100
U  125 4 175 1,3 2
U  160 5 175 1,3 2
6,3 175 2,6 3
U  200
8 175 2,6 3
U  250
U  320 10 175 2,6 3
12,5 175 3,3 3
U  400
16 175 5 3
U  500
U 630 20 175 6 5
U  800 25 175 6 5
32 175 8,3 5
U  1 000
U  1 250 32 175 12 10
U  1 600 32 175 13,3 10
32 175 13,3 10
U  2 000
40 175 13,3 10
U 2 500
U  3 200 50 175 16 14
U  4 000 63 175 21 14
80 175 27 14
U  5 000
U  6 300 100 175 33 25
U 8 000 125 175 41 25
160 175 55 40
U 10 000
a
When determining the required values for creepage and distance, the working voltage may be higher than
the voltage in the table by a factor of 1,1 (see Note).
NOTE The factor of 1,1 recognizes that at many places in a circuit, the working voltage equals the rated
voltage and that there are a number of rated voltages in common use that can be accommodated by the 1,1
factor.
b
If material with higher CTI value is used, the use of the Level of Protection “eb” creepage distances given for
that CTI in IEC 60079-7 is permitted.
c
At 10 V and below, the value of CTI is not relevant.

– 16 – IEC 60079-5:2015 © IEC 2015
4.8.4 Protective devices for temperature limitation
Temperature limitation may be achieved by an internal or external, electrical or thermal,
protective device. The device shall not be self-resetting.
Where integral fuses are used as protective devices, the fusing element shall be of the
enclosed type, for example, in glass or ceramic.
Over-current devices shall have a voltage rating not less than that of the circuit and shall have
a breaking capacity not less than the prospective fault current of the circuit.
4.8.5 Power supply prospective short-circuit current
Electrical equipment, parts of electrical equipment and Ex components protected by powder
filling “q”, with a rated voltage of not greater than 250 V a.c., shall be suitable for operation
from a supply system with a prospective short-circuit current of 1 500 A unless the marking
includes the value of the permitted prospective short-circuit current. Higher prospective
currents than 1 500 A could be present in some installations, for example at higher voltages.
If a current limiting device is necessary to limit the prospective short-circuit current to a value
not greater than the rated breaking capacity of the fuse, this device shall be a resistor
according to 4.8.3 a) and the rated values shall be:
– current rating 1,5 × 1,7 × I of the fuse;
n
– externally applied maximum voltage U ;
m
– power rating 1,5 × (1,7 × I of the fuse) × resistance of limiting device.
n
If the manufacturer does not provide a required short-circuit protective device, the certificate
number for the electrical equipment or parts of electrical equipment shall include the "X" suffix
in accordance with the marking requirements of IEC 60079-0 and the Specific Conditions of
Use listed on the certificate shall detail the short-circuit protective devices required.
5 Verifications and tests
5.1 Type verifications and tests
5.1.1 Pressure type test of container
The pressure tests shall be conducted on the samples subjected to the tests of enclosures in
IEC 60079-0. Irrespective of its volume, the container samples shall be subjected to a
pressure type test with an over-pressure of 50 kPa without the occurrence of permanent
deformation exceeding 0,5 mm in any of its dimensions. The pressure shall be applied for at
least 10 s.
For containers without breathing or degassing openings, which contain capacitors other than
plastic foil, paper or ceramic type and where the volume of the filling material is lower than
eight times the volume of the capacitors, the pressure type test with an overpressure of
1,5 MPa shall be applied for at least 10 s.
Where the reduced distances have been applied (4.3.1), the pressure test shall be conducted
hydraulically. There shall be no drops of water to blotting paper placed under the sample from
any of the joints of the sample not identified as a “gap” for the purposes of employing the
reduced distances.
NOTE 1 The test samples used for this test normally have the “gaps” sealed to allow the evaluation of the joints
without the drops of water expected to come from the “gaps”.
Tests may be conducted without the filling material present.

NOTE 2 When the container is also the external enclosure, the tests of enclosures requirements of IEC 60079-0
apply.
NOTE 3 The impact and drop tests of enclosures from IEC 60079-0 do not generally apply to Ex Components
intended to be mounted inside of another enclosure complying with IEC 60079-0, as the external enclosure
provides the protection against impact and drop.
5.1.2 Verification of the degree of protection of the enclosure
The degree of
...

IEC 60079-5 ®
Edition 4.1 2022-05
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 5: Equipment protection by powder filling "q"

Atmosphères explosives –
Partie 5: Protection du matériel par remplissage pulvérulent "q"

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IEC 60079-5 ®
Edition 4.1 2022-05
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 5: Equipment protection by powder filling "q"
Atmosphères explosives –
Partie 5: Protection du matériel par remplissage pulvérulent "q"
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-5711-1

IEC 60079-5 ®
Edition 4.1 2022-05
CONSOLIDATED VERSION
REDLINE VERSION
VERSIO N REDLINE
colour
inside
Explosive atmospheres –
Part 5: Equipment protection by powder filling "q"

Atmosphères explosives –
Partie 5: Protection du matériel par remplissage pulvérulent "q"

– 2 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Constructional requirements . 7
4.1 Containers . 7
4.1.1 Closing and sealing . 7
4.1.2 Pressure test of container . 8
4.1.3 Degree of protection of the container . 8
4.1.4 Filling procedure . 8
4.1.5 Containers that are not external enclosures . 8
4.2 Filling material . 9
4.2.1 Material specification . 9
4.2.2 Documentation . 9
4.2.3 Testing . 9
4.3 Distances . 9
4.3.1 Distances through filling material . 9
4.3.2 Distances surrounding free space . 11
4.4 Connections . 12
4.4.1 Equipment . 12
4.4.2 Ex Components . 12
4.5 Capacitors . 12
4.6 Cells and batteries . 12
4.7 Temperature limitations under overload conditions. 12
4.8 Temperature limitations under malfunction conditions . 12
4.8.1 General . 12
4.8.2 Fuse . 12
4.8.3 Malfunction exclusions . 13
4.8.4 Protective devices for temperature limitation. 16
4.8.5 Power supply prospective short-circuit current . 16
5 Verifications and tests . 16
5.1 Type verifications and tests . 16
5.1.1 Pressure type test of container . 16
5.1.2 Verification of the degree of protection of the enclosure . 17
5.1.3 Dielectric strength Insulation resistance test of the filling material . 17
5.1.4 Maximum temperatures . 17
5.2 Routine verifications and tests . 18
5.2.1 Routine pressure test of container . 18
5.2.2 Dielectric strength Insulation resistance test of the filling material . 18
6 Marking . 19
7 Instructions . 20
Bibliography . 21

Figure 1 – Distances through filling material . 11

© IEC 2022
Figure 2 – Test arrangement for the dielectric strength insulation resistance test of the
filling material . 19

Table 1 – Distances through the filling material . 10
Table 2 – Creepage distances and distances through filling material. 15

– 4 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 5: Equipment protection by powder filling “q”

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.
This consolidated version of the official IEC Standard and its amendment has been
prepared for user convenience.
IEC 60079-5 edition 4.1 contains the fourth edition (2015-02) [documents 31/1156/FDIS
and 31/1171/RVD] and its amendment 1 (2022-05) [documents 31/1601/CDV and
31/1171/RVD].
In this Redline version, a vertical line in the margin shows where the technical content
is modified by amendment 1. Additions are in green text, deletions are in strikethrough
red text. A separate Final version with all changes accepted is available in this
publication.
© IEC 2022
International Standard IEC 60079-5 has been prepared by IEC technical committee 31:
Equipment for explosive atmospheres.
This fourth edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
NOTE The technical changes referred to include the significant technical changes in the revised IEC standard, but
they do not form an exhaustive list of all modifications from the previous edition. More guidance may be found by
referring to the redline version of the IEC standard, if available.
Type
Minor and Major
Significant changes Clause/subclause Extension
editorial technical
changes changes
Specific references to IEC 60079-0 have been
reworded so the references to IEC 60079-0 can 4.1.3 4.8 4.8.3 X
be non-dated references
The “housing” surrounding the powder filled
equipment or Ex Component has been
redefined as a “container” to avoid confusion 4.1 X
with the “enclosure” requirements of
IEC 60079-0
A relaxation has been introduced to permit
reduced distances through filling material for
4.3.1 X
instances where there is no adjacent gap in the
container
A relaxation has been introduced to permit the
use of creepage dimensions per IEC 60079-7 4.8.3 X
where CTI is better than 175
An evaluation of joints employed when the
reduced distances according to Table 1 are 5.1.1 X
applied, has been added.
Text for determination of maximum temperature
clarified with respect to overloads and 5.1.4 X
malfunctions
A batch routine test has been introduced 5.2.1 X

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The list of all parts of IEC 60079 series, under the general title Explosive atmospheres, can
be found on the IEC website.
The committee has decided that the contents of the base publication and its amendment will
remain unchanged until the stability date indicated on the IEC web site under 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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
EXPLOSIVE ATMOSPHERES –
Part 5: Equipment protection by powder filling “q”

1 Scope
This part of IEC 60079 contains specific requirements for the construction, testing and
marking of electrical equipment, parts of electrical equipment and Ex components in the type
of protection powder filling “q”, intended for use in explosive gas atmospheres.
NOTE 1 Electrical equipment and Ex components protected by powder filling “q” can contain electronic circuits,
transformers, protection fuses, relays, intrinsically safe electrical apparatus, associated electrical apparatus,
switches, etc.
NOTE 2 Type of protection powder filling “q” provides Equipment Protection Level (EPL) Gb or Mb.
This standard supplements and modifies the general requirements of IEC 60079-0. Where a
requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of
this standard takes precedence.
This standard applies to electrical equipment, parts of electrical equipment and Ex
components with:
– a rated supply current less than or equal to 16 A;
– a rated supply voltage less than or equal to 1 000 V;
– a rated power consumption less than or equal to 1 000 W.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60079-0, Explosive atmospheres – Part 0: Equipment – General requirements
IEC 60079-7, Explosive atmospheres – Part 7: Equipment protection by increased safety "e"
IEC 60079-11, Explosive atmospheres – Part 11: Equipment protection by intrinsic safety "i"
IEC 60127 (all parts), Miniature fuses
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 61558-1, Safety of power transformers, power supplies, reactors and similar products –
Part 1: General requirements and tests
IEC 61558-2-6, Safety of transformers, reactors, power supply units and similar products for
supply voltages up to 1 100 V – Part 2-6: Particular requirements and tests for safety isolating
transformers and power supply units incorporating safety isolating transformers
ISO 2859-1, Sampling procedures for inspection by attributes – Part 1: Sampling schemes
indexed by acceptance quality limit (AQL) for lot-by-lot inspection

© IEC 2022
ISO 3310-1, Test sieves – Technical requirements and testing – Part 1: Test sieves of metal
wire cloth
ISO 3310-2, Test sieves – Technical requirements and testing – Part 2: Test sieves of
perforated metal plate
ISO 2591-1, Test sieving – Methods using test sieves of woven wire cloth and perforated
metal plate
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60079-0 as well as
the following apply.
NOTE Additional definitions applicable to explosive atmospheres can be found in IEC 60050-426.
3.1
powder filling “q”
type of protection in which the parts capable of igniting an explosive gas atmosphere are fixed
in position and completely surrounded by filling material to prevent the ignition of an external
explosive gas atmosphere
Note 1 to entry: The type of protection may not prevent the surrounding explosive gas atmosphere from
penetrating into the equipment and components and being ignited by the circuits. However, due to the small free
volumes in the filling material and due to the quenching of a flame which may propagate through the paths in the
filling material, an external explosion is prevented.
3.2
filling material
solid quartz or solid glass particles
3.3
container (for filling material)
housing immediately surrounding the electrical equipment protected by and containing the
filling material
Note 1 to entry: The container may, in some cases, also be the external enclosure.
4 Constructional requirements
4.1 Containers
4.1.1 Closing and sealing
4.1.1.1 General
Containers of electrical equipment, parts of electrical equipment or Ex components protected
by powder filling ”q” shall be filled and sealed at the time of manufacture. The closing and
sealing shall be the methods of 4.1.1.2 or 4.1.1.3.
4.1.1.2 Containers permanently sealed at the time of manufacture
The container shall be permanently sealed at the time of manufacture and shall not be
capable of being opened without leaving visible evidence that the container has been opened.
The container shall be marked in accordance with Clause 6, item a).
NOTE Suitable techniques that can provide visible evidence of containers being opened are, for example,
welding, soldering, cemented joints, rivets, cementing of screws, or lead-seal safety-wiring of screws.

– 8 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
4.1.1.3 Containers intended to be opened for repair
Electrical equipment, parts of electrical equipment, or Ex components that are designed to be
repaired shall incorporate sealing methods that are capable of being renewed without damage
to the container when the equipment is repaired, re-filled, and re-sealed. The container shall
be marked in accordance with Clause 6, item b).
4.1.2 Pressure test of container
The electrical equipment, parts of electrical equipment or Ex components protected by powder
filling “q” shall meet the pressure test requirements specified in 5.1.1.
4.1.3 Degree of protection of the container
The container of the electrical equipment, parts of electrical equipment, or Ex components
protected by powder filling “q”, in their normal service condition, i.e. with all openings closed
as in normal use, shall comply at least with the degree of protection IP54 as defined in
IEC 60529. If the degree of protection is IP55 or higher, and the container is not hermetically
sealed, the container shall be provided with a breathing device. The container with the
breathing device in place shall comply at least with the degree of protection IP54 according to
IEC 60529. The test shall be conducted on an empty container without the powder filling
installed. At the end of any water ingress tests, no water shall be visible inside the container.
NOTE 1 As the container may need to be destroyed in order to determine the entrance of dust or water, two
separate test samples could be required for the two ingress tests.
NOTE 2 When the container is also the external enclosure, the tests of enclosures requirements of IEC 60079-0
apply.
The ingress protection of containers or parts of electrical equipment protected by powder
filling “q”, intended for use only in clean, dry rooms, may be reduced to degree of protection
IP43. The certificate number of this equipment shall include the "X" suffix in accordance with
the marking requirements of IEC 60079-0, and the Specific Conditions of Use listed on the
certificate shall detail the restrictions of use.
When Ex components protected by powder filling “q” are intended to be mounted inside
another enclosure complying with IEC 60079-0, this outer enclosure shall have a degree of
protection of at least IP54. The IP rating of the inner container does not need to be specified
provided that the Ex component is mounted in a position where it is unlikely to be
contaminated by any small amounts of water that may enter the outer enclosure.
NOTE 3 The impact and drop tests of enclosures from IEC 60079-0 do not generally apply to Ex Components
intended to be mounted inside another enclosure complying with IEC 60079-0, as the external enclosure provides
the protection against impact and drop.
The maximum gap of a container protected by powder filling “q” shall be at least 0,1 mm
smaller than the specified smallest dimension of the filling material.
NOTE 4 The restriction on the size of the gap is intended to reduce the escape of filling material.
4.1.4 Filling procedure
Filling shall be carried out so as not to leave any void within the filling material (for example
by shaking down). The free space within electrical equipment, parts of electrical equipment or
Ex components protected by powder filling “q” shall be effectively filled with filling material
(see also 4.3.2).
4.1.5 Containers that are not external enclosures
The container of type of protection “q” equipment or Ex Component that is installed or
intended to be installed internal to another enclosure is considered the same as that of an Ex
Component.
© IEC 2022
4.2 Filling material
4.2.1 Material specification
The material shall be quartz or solid glass particles.
The material specification shall state that, determined in accordance with the ISO 2591-1
procedure for dry materials, the size of particles are within the following sieve sizes:
– 1 mm nominal aperture sieve in accordance with ISO 3310-1 or ISO 3310-2
– 500 µm nominal aperture sieve in accordance with ISO 3310-1.
4.2.2 Documentation
The documents prepared by the manufacturer in accordance with IEC 60079-0 shall include
the specification of the particle material, the size range of the particles, as well as the filling
process and the measures taken to ensure proper filling.
NOTE It is not a requirement of this standard that conformity to the specification of the particle material and size
range of the particles needs to be verified.
4.2.3 Testing
The filling material shall be subjected to the dielectric strength test specified in 5.1.3.
4.3 Distances
4.3.1 Distances through filling material
Except where specified otherwise in this standard, the minimum distance through the filling
material between electrically conducting parts of the equipment and the container shall
comply with Table 1 and Figure 1. This does not apply to conductors used for field wiring
connections which penetrate the wall of the container.

– 10 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
Table 1 – Distances through the filling material
a b
Voltage a.c. r.m.s. or d.c. Minimum distance Reduced distance
V mm mm
5 1,5
U ≤ 80
U ≤ 100 5 2
U ≤125 5 2
5 2
U ≤ 160
U ≤ 200 5 3
U ≤ 250 5 3
6,3 3
U ≤ 400
8 3
U ≤ 500
U ≤ 800 10 5
U ≤ 1 000 14 5
16 10
U ≤ 1 600
U ≤ 2 500 25 10
U ≤ 3 200 32 10
40 14
U ≤ 4 000
50 14
U ≤ 5 000
U ≤ 6 300 63 25
80 25
U ≤ 8 000
100 40
U ≤ 10 000
a
When determining the required values for creepage and distance, the working voltage may be higher than
the voltage in the table by a factor of 1,1 (see Note).
NOTE The factor of 1,1 recognizes that at many places in a circuit, the working voltage equals the rated
voltage and that there are a number of rated voltages in common use that can be accommodated by the 1,1
factor.
b
To ensure that there is a sufficient path length through the filling material to provide quenching of a flame
from the inside to the outside of the container, the reduced distances shown are permitted only when there
is no adjacent gap in the container that could permit a flame to exit. See Figure 1.

© IEC 2022
top
t
t
conductive (metallic) wall
a
c
gap
gap
b
c
solid
insulation
non-conductive non-conductive
wall wall
c
d
a d
conductive (metallic) wall
gap
bottom
IEC
Key
a
distance to conductive wall according Table 1, reduced distance
b
distance to non conductive wall with thickness t ; b ≥ (distance according Table 1) – t
c
distance to gap, minimum radius according Table 1, no reduced distance
d
creepage distance according Table 2
Figure 1 – Distances through filling material
Malfunction conditions according to 4.8 shall be considered when determining the working
voltage.
NOTE While this standard is applicable to equipment with a rated supply voltage not exceeding 1 000 V, Table 1
takes into account working voltages greater than 1 000 V which can be developed or generated within the
equipment or Ex Component. A typical example is a fluorescent luminaire ballast with a rated voltage of 240 V, but
with an arc initiation voltage of approximately 2 000 V.
4.3.2 Distances surrounding free space
If electrical equipment contains components which have an enclosed free space not filled with
the filling material (e.g. a relay), the following requirements apply:
– if the enclosed free space of the component is less than 3 cm , the minimum distance
through the filling material between the component wall and the inner surface of the
container shall comply with Table 1. The reduced distances are not permitted;
3 3
– if the enclosed free space of the component is between 3 cm and 30 cm , the minimum
distance through the filling material between the component wall and the inner surface of
the container shall comply with Table 1 but with a minimum of 15 mm;
– the component shall be fixed, so that movement nearer to the wall of the container is not
possible;
– the free volume shall not exceed 30 cm ;
– the enclosure of the component shall resist the thermal and mechanical stresses to which
it will be subjected even under malfunction conditions according to 4.8. There shall be no
damage or distortion which could reduce the protection provided by the filling material.

– 12 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
4.4 Connections
4.4.1 Equipment
Cables used for the entry of electrical conductors into a powder filled “q” container shall be an
integral part of the equipment and shall be protected and sealed as specified in 4.1.1. The
clamping means shall comply with the cable gland requirements of IEC 60079-0 and shall not
be capable of being removed without obvious damage to the powder filled “q” container.
4.4.2 Ex Components
Connection to powder filled “q” Ex Components shall comply with the connection facilities and
termination compartments requirements of IEC 60079-0.
4.5 Capacitors
The total stored energy of all capacitors in an enclosure of electrical equipment, part of
electrical equipment or Ex component protected by powder filling “q” shall not exceed 20 J in
normal operation.
4.6 Cells and batteries
Enclosures for powder filled “q” electrical equipment, parts of electrical equipment or Ex
components that contain cells or batteries shall incorporate a breathing device to the
surrounding atmosphere (see 4.1.3) unless the batteries or cells:
a) have a capacity of 1,5 Ah or less, or
b) do not release gas under normal operating conditions, and comply with the requirements
for primary and secondary batteries with a capacity up to 25 Ah, of IEC 60079-7, for level
of protection “eb”.
NOTE Sealed gas-tight cells do not release gas under normal operating conditions.
4.7 Temperature limitations under overload conditions
Each electrical equipment, part of electrical equipment or Ex component protected by powder
filling “q” shall be protected against overload prescribed in the relevant product standard
specified by the manufacturer so that the temperature class is not exceeded inside the filling
material at a depth of 5 mm from the wall of the container. If the reduced dimension of Table 1
has been applied and results in a distance less than 5 mm, the reduced distance shall be
used in place of the 5 mm shown. The effectiveness of the protection shall be confirmed by
the test of 5.1.4.
NOTE It is often difficult to limit the temperatures with only a fuse, and an internal thermal protective device is
often necessary to comply with the maximum temperature requirements of 5.1.4.
4.8 Temperature limitations under malfunction conditions
4.8.1 General
The container shall not be damaged and the temperature class shall not be exceeded even in
the case of malfunctions as detailed in 4.8. The effectiveness of the temperature protection
shall be confirmed by the test in 5.1.4.
4.8.2 Fuse
Unless the equipment supply is protected by a fuse rated at not more than 170 % of the
maximum normal current, the equipment shall be subjected to any single internal electrical
malfunction which may cause either an overvoltage or overcurrent, for example:
– short-circuit of any component;
– open circuit due to any component failure;

© IEC 2022
– malfunction in the printed circuitry.
Fuses, if employed, shall have a voltage rating not less than that of the circuit and shall have
a breaking capacity not less than the prospective fault current of the circuit.
If a malfunction can lead to one or more subsequent malfunctions, for example overloading of
a component, the primary and subsequent malfunctions are considered to be a single
malfunction.
Where there is no product standard, the overloads to be considered are those specified by the
manufacturer.
The voltage U shall be assumed to be applied to the supply terminals when considering
n
malfunction conditions and malfunction exclusions.
When the fuse is not integral to the electrical equipment or parts of electrical equipment, the
certificate number shall include the "X" suffix in accordance with the marking requirements of
IEC 60079-0 and the Specific Conditions of Use listed on the certificate shall detail the
required fuse.
When the fuse is not integral to an Ex component, the certificate number shall include the
symbol "U" in accordance with IEC 60079-0 and the schedule of limitations shall detail the
required fuse.
4.8.3 Malfunction exclusions
The following malfunctions need not be considered.
a) Resistance values lower than the rated values for:
– film type resistors,
– wire wound resistors and coils with a single layer in helical form,
when they are used at no more than 2/3 of their rated voltage and rated power at the
maximum service temperature as specified by the manufacturer of the respective
components.
b) Short-circuit conditions for:
– plastic foil capacitors,
– ceramic capacitors,
– paper capacitors,
when they are used at no more than 2/3 of their rated voltage as specified by the
manufacturer of the respective components.
c) Insulation failure of:
– galvanically separating components (e.g. optocouplers and relays) designed for
segregation of different circuits,
when the sum U of the r.m.s. values of the maximum voltages of the two circuits is not
more than 1 000 V and the rated voltage of the component between the two different
circuits is at least 1,5 times U.
NOTE Galvanically separating components providing double or reinforced insulation according to a product
standard are considered to meet the requirements of IEC 61140, e.g. IEC 60747-5-5 for photo coupler.
d) Transformers, coils and windings, which:
– comply with Level of Protection “eb” in IEC 60079-7, or
– comply with the requirements for mains transformers, Level of Protection “ia” or “ib”, in
IEC 60079-11, or
– comply with IEC 61558-2-6, or

– 14 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
– provide a double or reinforced insulation between the circuit per IEC 61558-1.
It is not necessary to consider the possibility of a short circuit if the distances or creepage
distances between bare live parts or printed tracks are at least equal to the values of Table 2
(for methods of measuring creepage distances see IEC 60079-7 and IEC 60079-11).
The maximum voltage between the parts shall be used to determine the distances according
to Table 2. If the parts are electrically isolated, the sum of the maximum voltages of the two
circuits shall be considered as the voltage. The maximum voltage shall be assessed taking
into account normal operating conditions (transients being disregarded) and malfunction
conditions as specified in this standard.
For distance under a coating according to Table 2, the following conditions apply:
– a conformal coating shall have the effect of sealing the conductors in question against
ingress of moisture;
– it shall adhere to the conductive parts and to the insulation material;
– if the conformal coating is applied by spraying, then two separate coats are to be applied;
– other methods of application require only one coat, for example, dip coating, brushing,
vacuum impregnating, but the intention is to achieve an effective, lasting, unbroken seal;
– a solder mask is considered as one of the two coatings, provided it is not damaged during
soldering.
Conductive parts protruding from the insulation (including soldered component pins) shall not
be considered as coated unless special measures have been applied to obtain an effective
unbroken seal.
Where bare parts of energized circuits emerge from the coating, the comparative tracking
index (CTI) in Table 2 applies to both insulation and conformal coating.

© IEC 2022
Table 2 – Creepage distances and distances through filling material
a
Voltage Creepage Minimum Distance under Distance through
b
a.c. or d.c. distance value coating filling material
U
r.m.s.
V mm CTI mm mm
c
U ≤ 10 1,6 0,6 1,5
–
U≤ 12,5 1,6 100 0,6 1,5
1,6 100 0,6 1,5
U ≤ 16
1,6 100 0,6 1,5
U≤ 20
U ≤ 25 1,7 100 0,6 1,5
U ≤ 32 1,8 100 0,7 1,5
3 100 0,7 1,5
U ≤ 40
U ≤ 50 3,4 100 0,7 1,5
U ≤ 63 3,4 100 1 1,5
3,6 100 1 1,5
U ≤ 80
3,8 100 1,3 2
U ≤ 100
U ≤ 125 4 175 1,3 2
U ≤ 160 5 175 1,3 2
6,3 175 2,6 3
U ≤ 200
U ≤ 250 8 175 2,6 3
U ≤ 320 10 175 2,6 3
12,5 175 3,3 3
U ≤ 400
U ≤ 500 16 175 5 3
U≤ 630 20 175 6 5
25 175 6 5
U ≤ 800
32 175 8,3 5
U ≤ 1 000
U ≤ 1 250 32 175 12 10
32 175 13,3 10
U ≤ 1 600
32 175 13,3 10
U ≤ 2 000
U≤ 2 500 40 175 13,3 10
U ≤ 3 200 50 175 16 14
63 175 21 14
U ≤ 4 000
U ≤ 5 000 80 175 27 14
U ≤ 6 300 100 175 33 25
125 175 41 25
U≤ 8 000
160 175 55 40
U≤ 10 000
a
When determining the required values for creepage and distance, the working voltage may be higher than
the voltage in the table by a factor of 1,1 (see Note).
NOTE The factor of 1,1 recognizes that at many places in a circuit, the working voltage equals the rated
voltage and that there are a number of rated voltages in common use that can be accommodated by the 1,1
factor.
b
If material with higher CTI value is used, the use of the Level of Protection “eb” creepage distances given for
that CTI in IEC 60079-7 is permitted.
c
At 10 V and below, the value of CTI is not relevant.

– 16 – IEC 60079-5:2015+AMD1:2022 CSV
© IEC 2022
4.8.4 Protective devices for temperature limitation
Temperature limitation may be achieved by an internal or external, electrical or thermal,
protective device. The device shall not be self-resetting.
Where integral fuses are used as protective devices, the fusing element shall be of the
enclosed type, for example, in glass or ceramic.
Over-current devices shall have a voltage rating not less than that of the circuit and shall have
a breaking capacity not less than the prospective fault current of the circuit.
4.8.5 Power supply prospective short-circuit current
Electrical equipment, parts of electrical equipment and Ex components protected by powder
filling “q”, with a rated voltage of not greater than 250 V a.c., shall be suitable for operation
from a supply system with a prospective short-circuit current of 1 500 A unless the marking
includes the value of the permitted prospective short-circuit current. Higher prospective
currents than 1 500 A could be present in some installations, for example at higher voltages.
If a current limiting device is necessary to limit the prospective short-circuit current to a value
not greater than the rated breaking capacity of the fuse, this device shall be a resistor
according to 4.8.3 a) and the rated values shall be:
– current rating 1,5 × 1,7 × I of the fuse;
n
– externally applied maximum voltage U ;
m
– power rating 1,5 × (1,7 × I of the fuse) × resistance of limiting device.
n
If the manufacturer does not provide a required short-circuit protective device, the certificate
number for the electrical equipment or parts of electrical equipment shall include the "X" suffix
in accordance with the marking requirements of IEC 60079-0 and the Specific Conditions of
Use listed on the certificate shall detail the short-circuit protective devices required.
5 Verifications and tests
5.1 Type verifications and tests
5.1.1 Pressure type test of container
The pressure tests shall be conducted on the samples subjected to the tests of enclosures in
IEC 60079-0. Irrespective of its volume, the container samples shall be subjected to a
pressure type test with an over-pressure of 50 kPa without the occurrence of permanent
deformation exceeding 0,5 mm in any of its dimensions. The pressure shall be applied for at
least 10 s.
For containers without breathing or degassing openings, which contain capacitors other than
plastic foil, paper or ceramic type and where the volume of the filling material is lower than
eight times the volume of the capacitors, the pressure type test with an overpressure of
1,5 MPa shall be applied for at least 10 s.
Where the reduced distances have been applied (4.3.1), the pressure test shall be conducted
hydraulically. There shall be no drops of water to blotting paper placed under the sample from
any of the joints of the sample not identified as a “gap” for the purposes of employing the
reduced distances.
NOTE 1 The test samples used for this test normally have the “gaps” sealed to allow the evaluation of the joints
without the drops of water expected to come from the “gaps”.
Tests may be conducted without the filling mater
...