EN ISO/IEC 80079-20-2:2016

SLOVENSKI STANDARD
01-julij-2016
1DGRPHãþD
SIST EN 13821:2003
Eksplozivne atmosfere - 20-2. del: Lastnosti materiala - Metode preskušanja
gorljivega prahu (ISO/IEC 80079-20-2:2016)
Explosive atmospheres - Part 20-2: Material characteristics - Combustible dusts test
methods (ISO/IEC 80079-20-2:2016)
Explosionsfähige Atmosphären - Teil 20-2: Werkstoffeigenschaften - Prüfverfahren für
brennbare Stäube (ISO/IEC 80079-20-2:2016)
Atmosphères explosives - Partie 20-2: Caractéristiques des produits - Méthodes d'essai
des poussières combustibles (ISO/IEC 80079-20-2:2016)
Ta slovenski standard je istoveten z: EN ISO/IEC 80079-20-2:2016
ICS:
13.220.40 Sposobnost vžiga in Ignitability and burning
obnašanje materialov in behaviour of materials and
proizvodov pri gorenju products
13.230 Varstvo pred eksplozijo Explosion protection
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO/IEC 80079-20-2
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2016
EUROPÄISCHE NORM
ICS 29.260.20 Supersedes EN 61241-2-2:1995
English Version
Explosive atmospheres - Part 20-2: Material
characteristics - Combustible dusts test methods (ISO/IEC
80079-20-2:2016)
Atmosphères explosives - Partie 20-2: Caractéristiques Explosionsfähige Atmosphären - Teil 20-2:
des produits - Méthodes d'essai des poussières Werkstoffeigenschaften - Prüfverfahren für brennbare
combustibles (ISO/IEC 80079-20-2:2016) Stäube (ISO/IEC 80079-20-2:2016)
This European Standard was approved by CEN on 18 February 2016.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO/IEC 80079-20-2:2016 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 2014/34/EU . 4
Annex ZB (informative) Significant changes with respect to IEC 61241-2-1:1994, EN 61241-
2-2:1993 and IEC 61241-2-3:1994 . 5

European foreword
This document (EN ISO/IEC 80079-20-2:2016) has been prepared by Technical Committee ISO/TMBG
"Technical Management Board - groups" in collaboration with Technical Committee CEN/TC 305
“Potentially explosive atmospheres - Explosion prevention and protection” the secretariat of which is
held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by September 2016, and conflicting national standards
shall be withdrawn at the latest by September 2016.
The significant changes with respect to EN 61241-2:1995 are included in Annex ZB “Significant changes
with respect to IEC 61241-2-1:1994, IEC 61241-2-2:1993 and IEC 61241-2-3:1994".
This document supersedes EN 61241-2-2:1995.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association, and supports essential requirements of 2014/34/EU.
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this
document.
Extensions to the marking scheme described in the Directive are found in the ATEX Guidelines
published by the European Commission. These are particularly useful for equipment that conforms to
more than one category.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent
rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO/IEC 80079-20-2:2016 has been approved by CEN as EN ISO/IEC 80079-20-2:2016
without any modification.
Annex ZA
(informative)
Relationship between this European Standard and the Essential
Requirements of EU Directive 2014/34/EU
This European Standard has been prepared under a mandate given to CEN by the European
Commission and the European Free Trade Association to provide a means of conforming to Essential
Requirements of the New Approach Directive 2014/34/EU.
Once this standard is cited in the Official Journal of the European Union under that Directive and has
been implemented as a national standard in at least one Member State, compliance with the clauses of
this standard given in table ZA confers, within the limits of the scope of this standard, a presumption of
conformity with the corresponding Essential Requirements of that Directive and associated EFTA
regulations.
Table ZA.1 — Correspondence between this European Standard and Directive 2014/34/EU
Clause(s)/sub-clause(s) of this Essential Requirements (ERs) Qualifying remarks/Notes
EN of Directive 2014/34/EU
5, 6, Annex G Annex II, Clause 1.01; 1.0.6a;
1.0.6b; 1.2.1; 1.2.4; 1.5.7
WARNING — Other requirements and other EU Directives may be applicable to the product(s) falling
within the scope of this standard.

Annex ZB
(informative)
Significant changes with respect to IEC 61241-2-1:1994, EN 61241-2-2:1993
and IEC 61241-2-3:1994
This European Standard supersedes IEC 61241-2-1:1994, EN 61241-2-2:1993 and IEC 61241-2-3:1994
Table ZB.1 — Significant changes with respect to IEC 61241-2-1:1994, EN 61241-2-2:1993 and
IEC 61241-2-3:1994
Type
Explanation of the significance of the Clause Minor and Extension Major
changes editorial technical
changes changes
Normative references 2 X
Terms and Definitions 3 X
Dust sample Requirements 4 X
Combustible Dust Determination 5 X
Procedure for Characterisation of 6 X
combustible dust or combustible flying
Test methods for determination of a 7 X
combustible dust or a combustible flying
MIT of a dust cloud 8.1 X
MIT of a dust layer 8.2 X
MIE of a dust/air mixture 8.3 X
Tests on resistivity 8.4 X
Measurement of temperature Annex X
distribution on the surface of the hot A
plate
Godbert-Greenwald oven Annex X
B
Examples of spark-generating systems Annex X
C
Table ZB.1 (continued)
Type
Explanation of the significance Clause Minor and editorial Extension Major technical
of the changes changes changes
Vertical tube apparatus Annex X
D
20-litre sphere Annex X
E
BAM oven Annex X
F
Data for dust explosion Annex X
characteristics G
1m vessel Annex X
H
NOTE 1 The technical changes referred to include the significant technical changes from the revised EN but this
is not an exhaustive list of all modifications from the previous version.
Explanations:
A) Definitions
Minor and editorial changes clarification
decrease of technical requirements
minor technical change
editorial corrections
Changes in a standard classified as ‘Minor and editorial changes’ refer to changes regarding the
previous standard, which modify requirements in an editorial or a minor technical way. Also changes of
the wording to clarify technical requirements without any technical change are classified as ‘Minor and
editorial changes’.
A reduction in level of existing requirement is also classified as ‘Minor and editorial changes’
Extension addition of technical options
Changes in a standard classified as ‘extension’ refers to changes regarding the previous standard, which
add new or modify existing technical requirements, in a way that new options are given, but without
increasing requirements for equipment that was fully compliant with the previous standard. Therefore
these ‘extensions’ will not have to be considered for products in conformity with the preceding edition.
Major technical changes addition of technical requirements
increase of technical requirements
Changes in a standard classified as ‘Major technical change’ refer to changes regarding the previous
standard, which add new or increase the level of existing technical requirements, in a way that a
product in conformity with the preceding standard will not always be able to fulfil the requirements
given in the standard. ‘Major technical changes’ have to be considered for products in conformity with
the preceding edition. For every change classified as ‘Major Technical Change’ additional information is
provided in clause B) of the Annex ZB.
NOTE 2 These changes represent current technological knowledge . However, these changes should not
normally have an influence on equipment already placed on the market.
B) Information about the background of ‘Major Technical Changes’
None
see also ATEX Guideline 10.3 and Annex ZA
ISO/IEC 80079-20-2
Edition 1.0 2016-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 20-2: Material characteristics – Combustible dusts test methods

Atmosphères explosives –
Partie 20-2: Caractéristiques des produits – Méthodes d’essai des poussières

combustibles
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 13.230; 29.260.20 ISBN 978-2-8322-3179-1

– 2 – ISO/IEC 80079-20-2:2016
 ISO/IEC 2016
CONTENTS
FOREWORD . 5
1 Scope . 8
2 Normative references. 8
3 Terms and definitions . 8
4 Dust sample requirements . 9
4.1 Receipt of sample for testing . 9
4.2 Characterisation of sample . 9
4.3 Preparation of sample . 10
4.4 Test conditions . 10
5 Combustible dusts and combustible flyings determination . 10
5.1 Test sequence . 10
5.2 Tests to determine whether material is a combustible dust or combustible
flying . 10
5.2.1 Visual inspection . 10
5.2.2 Determine particle distribution . 11
5.2.3 Ignition test in the Hartmann tube . 11
5.2.4 Ignition test in the 20-litre sphere . 11
6 Procedure for characterisation of combustible dust or combustible flying . 11
7 Test methods for determination of whether a material is a combustible dust or a
combustible flying . 14
7.1 Modified Hartmann tube . 14
7.1.1 General . 14
7.1.2 Test equipment . 14
7.1.3 Test procedure . 15
7.2 20-litre sphere . 15
7.2.1 General . 15
7.2.2 Test equipment . 15
7.2.3 Test procedure . 16
7.3 Alternative method to 20-litre sphere for small test material quantities . 16
7.3.1 General . 16
7.3.2 Test equipment . 17
7.3.3 Test procedure . 17
8 Test methods for combustible dust determinations . 17
8.1 MIT of a dust cloud . 17
8.1.1 General . 17
8.1.2 GG furnace . 17
8.1.3 BAM furnace . 18
8.2 Test for MIT of dust layer . 19
8.2.1 General . 19
8.2.2 Heated surface . 19
8.2.3 Dust layers . 20
8.2.4 Dust layer temperature . 20
8.2.5 Ambient temperature measurements . 20
8.2.6 Dust layer temperature test method . 20
8.2.7 Recording of results . 21
8.3 Method for determining minimum ignition energy of dust/air mixtures . 22

ISO/IEC 80079-20-2:2016 – 3 –
 ISO/IEC 2016
8.3.1 General . 22
8.3.2 Test equipment . 22
8.3.3 Test procedure . 23
8.3.4 Calibration for determination of minimum ignition energies (MIE) by
electrically generated high-voltage d.c. sparks . 24
8.3.5 Recording of test results . 24
8.4 Test on resistivity . 24
8.4.1 General . 24
8.4.2 Test equipment . 25
8.4.3 Test procedure . 25
8.4.4 Recording of test results . 26
9 Test report. 26
Annex A (normative) Measurement of temperature distribution on the surface of the
hot plate . 27
Annex B (informative) Godbert-Greenwald oven (GG) . 28
Annex C (informative) Examples of spark-generating systems . 29
C.1 General . 29
C.2 Triggering by auxiliary spark using three-electrode system . 30
C.3 Triggering by electrode movement . 31
C.4 Triggering by voltage increase (trickle-charging circuit) . 32
C.5 Triggering by auxiliary spark, using normal two-electrode system – Trigger
transformer in discharge circuit . 33
Annex D (normative) Vertical tube (modified Hartmann tube) apparatus . 34
Annex E (informative) 20-litre sphere . 35
Annex F (informative) BAM oven . 37
Annex G (informative) Data for dust explosion characteristics . 38
Annex H (informative) 1 m vessel . 39
H.1 Test principle . 39
H.2 Test apparatus . 39
H.3 Test conditions . 43
H.4 Test procedure . 43
Bibliography . 45

Figure 1 – Protocol for characterisation of combustible dust or combustible flying . 12
Figure 2 – Tests to define ability to form explosive dust atmosphere (combustible
dust/combustible flyings) . 13
Figure 3 – Tests to characterise combustible dust or combustible flying . 14
Figure 4 – Modified Hartmann tube . 23
Figure 5 – Measuring cell for powder resistivity . 25
Figure A.1 – Typical surface temperature distribution (method A) . 27
Figure B.1 – Vertical cross-section through the Godbert-Greenwald oven . 28
Figure C.1 – Circuit – Triggering by high-voltage relay, using a two-electrode system . 29
Figure C.2 – Apparatus for determining the minimum ignition energies of dust
(schematic) – Triggering by auxiliary spark using three-electrode system . 30
Figure C.3 – Apparatus for determining the minimum ignition energies of dust
(schematic) – Triggering by electrode movement . 31
Figure C.4 – Apparatus for determining the minimum ignition energies of dust
(schematic) – Triggering by voltage increase . 32

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 ISO/IEC 2016
Figure C.5 – Apparatus for determining the minimum ignition energies for dust
(schematic) – Trigger transformer in discharge circuit . 33
Figure D.1 – Vertical tube apparatus (modified Hartmann tube) . 34
Figure E.1 – Test equipment 20-litre sphere (schematic) . 35
Figure E.2 – Cross-sectional view of rebound nozzle . 36
Figure E.3 – Plan view of rebound nozzle . 36
Figure E.4 – Cross-sectional view of dispersion cup . 36
Figure F.1 – Cross-sectional arrangement of BAM oven . 37
Figure H.1 – 1 m vessel (schematic) . 40
Figure H.2 – Location of the 6 mm holes in the semicircular dust dispenser . 41
Figure H.3 – Rebound nozzle . 42
Figure H.4 – Dispersion cup . 43

Table 1 – Example of ignition test report . 21

ISO/IEC 80079-20-2:2016 – 5 –
 ISO/IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 20-2: Material characteristics –
Combustible dusts test methods

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard ISO/IEC 80079-20-2 has been prepared by subcommittee 31M: Non-
electrical equipment and protective systems for explosive atmospheres, of IEC 31: Equipment
for explosive atmospheres.
It is published as a double logo standard.
This first edition cancels and replaces the first edition of IEC 61241-2-1 published in 1994, the
first edition of IEC 61241-2-2 published in 1993 and the first edition of IEC 61241-2-3
published in 1994, combining the requirements into a single document, and is considered to
constitute a technical revision.

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 ISO/IEC 2016
The text of this standard is based on the following documents:
FDIS Report on voting
31M/102/FDIS 31M/108/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. In ISO, the standard has been approved by 15 P-members
out of 21 having cast a vote.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
"A list of all parts in the IEC 60079 series, under the general title Explosive atmospheres, as
well as the International Standard 80079 series, 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 web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
ISO/IEC 80079-20-2:2016 – 7 –
 ISO/IEC 2016
Significant changes with respect to IEC 61241-2-1:1994, IEC 61241-2-2:1993 and
IEC 61241-2-3:1994
Type
Explanation of the significance of the Clause Minor and Extension Major technical
changes editorial changes changes
Normative references 2 X
Terms and Definitions 3 X
Dust sample Requirements 4 X
Combustible Dust Determination 5 X
Procedure for Characterisation of combustible 6 X
dust or combustible flying
Test methods for determination of a 7 X
combustible dust or a combustible flying
MIT of a dust cloud 8.1 X
MIT of a dust layer 8.2 X
MIE of a dust/air mixture 8.3 X
Tests on resistivity 8.4 X
Measurement of temperature distribution on Annex X
the surface of the hot plate A
Godbert-Greenwald oven Annex X
B
Examples of spark-generating systems Annex X
C
Vertical tube apparatus Annex X
D
20-litre sphere Annex X
E
BAM oven Annex F X
Data for dust explosion characteristics Annex X
G
1m vessel Annex X
H
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 ISO/IEC 2016
EXPLOSIVE ATMOSPHERES –
Part 20-2: Material characteristics –
Combustible dusts test methods

1 Scope
This part of ISO/IEC 80079 describes the test methods for the identification of combustible
dust and combustible dust layers in order to permit classification of areas where such
materials exist for the purpose of the proper selection and installation of electrical and
mechanical equipment for use in the presence of combustible dust.
The standard atmospheric conditions for determination of characteristics of combustible dusts
are:
• temperature –20 °C to +60 °C,
• pressure 80 kPa (0,8 bar) to 110 kPa (1,1 bar) and
• air with normal oxygen content, typically 21 % v/v.
The test methods defined do not apply to:
• recognized explosives, propellants (e.g. gunpowder, dynamite), or substances or mixtures
of substances which may, under some circumstances, behave in a similar manner or
• dusts of explosives and propellants that do not require atmospheric oxygen for
combustion, or to pyrophoric substances.
2 Normative references
None.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
combustible dust
finely divided solid particles, 500 µm or less in nominal size, which may form explosive
mixtures with air at standard atmospheric pressure and temperatures
Note 1 to entry: This includes dust and grit as defined in ISO 4225.
Note 2 to entry: The term 'solid particles' is intended to address particles in the solid phase but does not preclude
a hollow particle.
3.1.1
conductive dust
combustible metal dusts and other combustible dusts with electrical resistivity equal to or less
than 1 × 10 Ω⋅m
Note 1 to entry: Metal dust is treated as conductive dust because it is assumed that surface oxidation cannot be
depended upon to always ensure electrical resistivity greater than 1 × 10 Ω⋅m

ISO/IEC 80079-20-2:2016 – 9 –
 ISO/IEC 2016
3.1.2
non-conductive dust
combustible dust with electrical resistivity greater than 1 × 10 Ω⋅m
3.2
combustible flyings
solid particles, including fibres, where one dimension is greater than 500 µm in nominal size,
which may form an explosive mixture with air at standard atmospheric pressure and
temperature
Note 1 to entry: The ratio of length to width is 3 or more.
Note 2 to entry: Examples of flyings include carbon fibre, rayon, cotton (including cotton linters and cotton waste),
sisal, jute, hemp, cocoa fibre, oakum and baled waste kapok.
3.3
explosive dust atmosphere
mixture with air, under atmospheric conditions, of combustible substances in the form of dust,
fibres, or flyings which, after ignition, permits self-sustaining propagation
3.4
minimum ignition temperature of a dust layer
lowest temperature of a hot surface at which ignition occurs in a dust layer under specified
test conditions
3.5
minimum ignition temperature of a dust cloud
lowest temperature of a hot surface on which the most ignitable mixture of the dust with air is
ignited under specified test conditions
3.6
minimum ignition energy (of a combustible dust/air mixture)
lowest electrical energy stored in a capacitor which upon discharge is sufficient to effect
ignition of the most sensitive dust/air mixture under specified test conditions
4 Dust sample requirements
4.1 Receipt of sample for testing
A material safety data sheet or equivalent with the sample.
The test material shall be provided in suitable packaging, labelled according to relevant
guidelines labelled according to relevant guidelines, and appropriate transportation.
NOTE It is usual to provide a quantity of at least 0,5 kg for testing. If sample preparation is required this may be
insufficient. If only a smaller volume of material is available then the full range of testing may not be possible.
4.2 Characterisation of sample
The sample shall be representative of the material as it appears in the entire process
operated.
NOTE Many unit operations such as extract systems will separate dust into finer fractions than seen in the main
processing equipment and this is accounted for when taking the sample.
If the sample is not representative of the material as found in the process then sample
preparation shall be carried out to apply the worst case conditions.
At least the following information about the sample shall be provided:

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 ISO/IEC 2016
– minimum particle size,
– median particle size,
– maximum particle size,
– particle distribution,
– moisture content, and
– method of determination (e.g. optical methods or sieving).
If the applicant cannot provide usable data then this shall be determined separately.
4.3 Preparation of sample
If it is not possible to test the sample as received, or if the sample is no longer representative
of the process material then it may be necessary to condition or alter the sample for testing.
This may include
– grinding/sieving,
– drying and
– humidifying.
Any apparent changes noted in the properties of the dust during preparation of the sample, for
example, by sieving or owing to temperature or humidity conditions, shall be stated in the test
report.
NOTE 1 Sample preparation such as grinding and sieving, or drying can alter the material characteristics. Where
finer fractions are present in a facility it is appropriate to take fractions of less than 63 µm to give the most easily
ignitable mixtures. When the sample is a mixture of substances, the sample preparation can result in a change to
the sample’s composition.
NOTE 2 The presence of solvents can become altered in the sample preparation process.
4.4 Test conditions
+10
The tests shall be carried out at standard atmospheric temperature of 20 °C and standard
−10
atmospheric pressure of 80 kPa to 110 kPa (0,8 bar to 1,1 bar) unless otherwise specified.
5 Combustible dusts and combustible flyings determination
5.1 Test sequence
The sequence followed for the determination of the material properties of combustible dust
and combustible flyings is given in 5.2, Clause 6 and Figure 1, Figure 2 and Figure 3.
NOTE 1 Refer also to the information referenced in Annex G.
NOTE 2 Testing in the Hartman tube is a screening method. The test procedure can be directly started with the
20 litre sphere or the GG Oven.
5.2 Tests to determine whether material is a combustible dust or combustible flying
5.2.1 Visual inspection
Make a visual inspection of the test material (by microscope if necessary) to determine
whether the material consists of combustible flyings:
• If the material consists of combustible flyings with dust then continue the test procedure in
a Hartmann tube (see 5.2.3) to determine whether the combination of the two is
combustible dust.
• If the material consists only of combustible flyings then continue the test procedure in a
Hartmann tube (see 5.2.3) to determine whether it is combustible flyings.

ISO/IEC 80079-20-2:2016 – 11 –
 ISO/IEC 2016
5.2.2 Determine particle distribution
For material which does not contain combustible flyings check the particle size distribution:
• If there are no particles less than 500 µm in size then the material is not a combustible
dust.
• If there are any particles less than 500 µm in size then continue the test procedure in a
Hartmann tube to determine whether it is a combustible dust.
5.2.3 Ignition test in the Hartmann tube
5.2.3.1 Test in a Hartmann tube with a spark (see 7.1):
1) If ignition occurs, the material is a combustible dust or a combustible flying (proceed to the
procedure for characterisation of combustible dust or combustible flying (see Clause 6)).
2) If no ignition occurs:
a) proceed to a Hartmann tube with a hot coil ignition source (see 7.1);
b) it can be assumed that the minimum ignition energy is greater than 1 J and the test
material is hard to ignite.
5.2.3.2 Test in a Hartmann tube with a hot coil ignition source (see 7.1):
1) If ignition occurs, the material is a combustible dust or a combustible flying, (proceed to
the procedure for the characterisation of combustible dust or combustible flying (see
Clause 6).
2) If no ignition occurs:
a) proceed to the test in the 20-litre sphere (see 7.2);
b) it can be assumed that the minimum ignition energy is greater than 10 J.
5.2.4 Ignition test in the 20-litre sphere
Test in the 20-litre sphere (see 7.2):
• If ignition occurs the material is a combustible dust or a combustible flying (proceed to
procedure for characterisation of combustible dust or combustible flying (see Clause 6)).
• If no ignition occurs then the material is not a combustible dust or a combustible flying and
the testing procedure is completed.
NOTE Although the material does not form explosive mixtures with air, it can still ignite as a combustible dust
layer.
If there is insufficient material available for testing in a 20-litre sphere then testing in the
Godbert-Greenwald (GG) oven at 1 000 °C is an acceptable alternative (see 7.3):
• If no ignition occurs at 1 000 °C then the material is not a combustible dust or a
combustible flying.
• If there is an ignition at 1 000 °C then the material should be subject to further verification
in the 20-litre sphere before declaring it combustible or non-combustible.
6 Procedure for characterisation of combustible dust or combustible flying
The following is the procedure for the characterisation of combustible dust or combustible
flying:
– test for dust cloud minimum ignition temperature (MIT) (see Clause 8):
a) GG oven (see 8.1.2) or
b) BAM oven (see 8.1.3)
– test for dust layer MIT (see 8.2);

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 ISO/IEC 2016
– test for minimum ignition energy (MIE) of dust cloud (see 8.3);
– test for resistivity of bulk dust (see 8.4).

IEC
Figure 1 – Protocol for characterisation of combustible dust or combustible flying

ISO/IEC 80079-20-2:2016 – 13 –
 ISO/IEC 2016
IEC
Figure 2 – Tests to define ability to form explosive dust atmosphere
(combustible dust/combustible flyings)

– 14 – ISO/IEC 80079-20-2:2016
 ISO/IEC 2016
IEC
Figure 3 – Tests to characterise combustible dust or combustible flying
7 Test methods for determination of whether a material is a combustible dust
or a combustible flying
7.1 Modified Hartmann tube
7.1.1 General
Dust is dispersed in a tube to form a dust cloud, and ignition trials are attempted with two
different ignition sources.
7.1.2 Test equipment
The test equipment consists of a vertical tube closed at the bottom with a dispersion cup
(volume approximately 1,2 l, internal diameter (70 ± 5) mm).
As ignition sources
ISO/IEC 80079-20-2:2016 – 15 –
 ISO/IEC 2016
– a continuous induction spark (electrode gap of approximately 4 mm, with a transformer
rated approximately 15 kV, and approximately 0,2 kVA),
– a glowing coil (wire diameter approximately 1,2 mm, wire length approximately 470 mm,
coil diameter approximately 11 mm and wire temperature at least 1 000 °C)
The vertical separation between the bottom of the dispersion cup and the ignition source is
approximately 100 mm.
A detailed description of suitable equipment can be found in Annex D.
7.1.3 Test procedure
The test sample is deposited in the dispersion cup and dispersed with a blast of air (50 cm ,
700 kPa to 800 kPa gauge). The dust concentration is varied over a wide range from 250 g/m
3 3 3 3 3 3
to 1500 g/m (typically 250 g/m , 500 g/m , 750 g/m , 1 000 g/m and 1 500 g/m ) and the
behaviour is visually observed. The different quantities are each tested once, but repeated
dispersions are made for at least 3 attempts.
If a flame propagates from the ignition source, the test material is a combustible dust or
combustible flying.
If no ignitions are observed with the spark ignition source, then the coil ignition source is
used. Testing may be stopped immediately after an ignition is observed.
If it is unclear, whether ignition has been observed then the 20-litre sphere test shall be used.
NOTE 1 In the case of high density materials such as metals higher concentrations (e.g. up to 2 500 g/m ) are
used.
NOTE 2 Deposits on the coil can result in localised smouldering or burning, which is not considered as ignition.
7.2 20-litre sphere
7.2.1 General
Dust is dispersed in a pressure resistant closed apparatus (20-litre sphere) to form a dust
cloud under standard conditions of pressure and temperature. Ignition trials are attempted
with pyrotechnic igniters.
As an alternative method, the 1 m vessel can be used (see Annex H).
7.2.2 Test equipment
The standard
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