IEC 60079-29-2:2015

IEC 60079-29-2 ®
Edition 2.0 2015-03
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 29-2: Gas detectors – Selection, installation, use and maintenance of
detectors for flammable gases and oxygen

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
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IEC 60079-29-2 ®
Edition 2.0 2015-03
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Explosive atmospheres –
Part 29-2: Gas detectors – Selection, installation, use and maintenance of

detectors for flammable gases and oxygen

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.260.20 ISBN 978-2-8322-2455-7

– 2 – IEC 60079-29-2:2015 RLV  IEC 2015

CONTENTS
FOREWORD . 8
INTRODUCTION . 11
1 Scope . 13
2 Normative references . 14
3 Terms and definitions . 15
3.1 Gas properties and other physics . 15
3.2 Types of equipment . 17
3.3 Sensors and detectors . 18
3.4 Supply of gas to instruments . 20
3.5 Signals and alarms . 20
3.6 Times, checks and equipment behaviour . 21
3.7 Terms exclusive to open path equipment . 22
4 Basic information on the properties, behaviour, and detection of gases and
vapours, and specific applications of gas detection . 24
4.1 Detecting gases and vapours – General . 24
4.1.1 General . 24
4.1.2 Safety when monitoring for flammable gases where personnel could be
present . 25
4.2 Some common properties of gases and vapours . 26
4.3 The differences between detecting gases and vapours . 27
4.3.1 General . 27
4.3.2 Detection of gases . 27
4.3.3 Detection of vapours . 29
4.4 Oxygen deficiency. 32
4.4.1 General . 32
4.4.2 Chemical reaction of oxygen, with solid products . 32
4.4.3 Chemical reaction of oxygen, with gaseous products . 33
4.4.4 Dilution of the air by displacement by some other gas or vapour . 33
4.5 Specific applications of gas detection . 34
4.5.1 Gas detection as means of reducing risk of explosion . 34
4.5.2 Gas free work permit . 36
4.5.3 Monitoring of air inlets . 37
4.6 Specific considerations for open path detection . 38
5 Measuring principles . 39
5.1 General . 39
5.2 Catalytic sensors . 41
5.2.1 General . 41
5.2.2 Common applications . 41
5.2.3 Limitations . 41
5.2.4 Interferences . 42
5.2.5 Poisoning . 42
5.3 Thermal conductivity sensors . 43
5.3.1 General . 43
5.3.2 Common applications . 43
5.3.3 Limitations . 44
5.3.4 Interferences . 44

5.3.5 Poisoning . 44
5.4 Infrared sensors . 44
5.4.1 General . 44
5.4.2 Common applications . 45
5.4.3 Limitations . 45
5.4.4 Interferences . 46
5.4.5 Poisoning . 46
5.5 Semiconductor sensors . 46
5.5.1 General . 46
5.5.2 Common applications . 46
5.5.3 Limitations . 47
5.5.4 Interferences . 47
5.5.5 Poisoning . 47
5.6 Electrochemical sensors . 48
5.6.1 General . 48
5.6.2 Common applications . 48
5.6.3 Limitations . 48
5.6.4 Interferences . 49
5.6.5 Poisoning . 49
5.7 Flame ionization detectors (FID) . 49
5.7.1 General . 49
5.7.2 Common applications . 49
5.7.3 Limitations . 50
5.7.4 Interferences . 50
5.7.5 Poisoning . 50
5.8 Flame temperature analysers (FTA) . 50
5.8.1 General . 50
5.8.2 Common applications . 50
5.8.3 Limitations . 50
5.8.4 Interferences . 51
5.8.5 Poisoning . 51
5.9 Photo ionisation detector (PID) . 51
5.9.1 General . 51
5.9.2 Common applications . 51
5.9.3 Limitations . 51
5.9.4 Interferences . 52
5.9.5 Poisoning . 52
5.10 Paramagnetic oxygen detector . 52
5.10.1 General . 52
5.10.2 Common applications . 52
5.10.3 Limitations . 53
5.10.4 Interference . 53
5.10.5 Poisoning . 53
6 Selection of apparatus equipment . 53
6.1 General . 53
6.2 Selection criteria . 54
6.2.1 General criteria . 54
6.2.2 Gases to be detected by the apparatus equipment . 55
6.2.3 Intended Application of the apparatus fixed equipment . 56

– 4 – IEC 60079-29-2:2015 RLV  IEC 2015

6.2.4 Application of transportable and portable equipment . 60
6.3 Miscellaneous factors affecting selection of apparatus equipment . 61
6.3.1 Electromagnetic immunity . 61
6.3.2 Intended Zone(s) of use . 61
7 Behaviour of gas releases . 61
7.1 Nature of a release . 61
7.1.1 General . 61
7.1.2 Release rate of gas or vapour . 62
7.1.3 Flammable limits . 62
7.1.4 Ventilation . 63
7.1.5 Relative density of the released gas or vapour. 63
7.1.6 Temperature and/or pressure. 63
7.1.7 Other parameters to be considered . 63
7.1.8 Outdoor sites and open structures . 64
7.2 Buildings and enclosures . 64
7.2.1 General . 64
7.2.2   Unventilated buildings and enclosures . 64
7.2.3  Ventilated buildings and enclosures . 64
7.3 Environmental considerations . 65
8 Design and installation of fixed gas detection systems . 66
8.1 General . 66
8.2 Basic considerations for the installation of fixed systems . 66
8.2.1 General . 66
8.2.2 Point detection equipment and remote sensors . 67
8.2.3 Systems consisting of sampling equipment . 67
8.2.4 Open path (line of sight) equipment . 67
8.3 Location of detection points . 68
8.3.1 General . 68
8.3.2 General site considerations . 68
8.3.3 Environmental conditions . 69
8.4 Access for calibration and maintenance . 71
8.5 Additional considerations for sample lines . 72
8.6 Additional considerations for open path equipment . 73
8.7 Summary of considerations for the location of sensors or sampling
measuring points and open paths . 73
8.8 Installation of sensors measuring point and open path equipment . 74
8.9 Integrity and safety of fixed systems . 74
8.9.1 General . 74
8.9.2 Redundancy in fixed systems. 75
8.9.3 Protection against loss of main power supply . 75
8.10 Timing of installation during construction operations . 75
8.11 Commissioning . 75
8.11.1 Inspection . 75
8.11.2 Initial gas calibration . 76
8.11.3 Adjustment of alarm set points . 76
8.12 Operating instructions, plans and records . 77
9 Use of portable and transportable flammable gas detection apparatus equipment . 77
9.1 General . 77

9.2 Initial and periodic check procedures for portable and transportable
instrumentation . 79
9.2.1 General . 79
9.2.2 Inspection and field functional checks (response check) . 79
9.2.3 Routine checks tests and recalibration . 80
9.2.4 Maintenance and recalibration . 81
9.3 Guidance on the use of portable and transportable apparatus equipment . 81
9.3.1 Electrical safety in hazardous atmospheres . 81
9.3.2 Safety of personnel . 81
9.3.3 Spot tests and sampling . 82
9.3.4 Sampling above liquids . 82
9.3.5 Avoidance of condensation . 82
9.3.6 Poisoning of sensors . 83
9.3.7 Changes of temperature . 83
9.3.8 Accidental damage . 83
9.3.9 Minimalist operation, the “Read and run” concept . 83
10 Training of operational personnel . 84
10.1 General . 84
10.2 General training – Basic limitations and safety . 84
10.3 Operator training . 85
10.4 Maintenance training . 85
11 Maintenance, routine procedures and general administrative control . 85
11.1 General . 85
11.2 Operational checks . 87
11.2.1 General . 87
11.2.2 Fixed systems . 87
11.2.3 Portable and transportable gas detection apparatus equipment . 88
11.3 Maintenance . 89
11.3.1 General . 89
11.3.2 Fixed apparatus equipment . 89
11.3.3 Portable and transportable gas detection apparatus equipment . 89
11.3.4 Off-site maintenance, general . 89
11.3.5 Maintenance procedures. 90
11.4 Sensors . 90
11.4.1 General . 90
11.4.2 Flame arrestor . 90
11.5 Flow systems . 90
11.5.1 General . 90
11.5.2 Inspection . 91
11.5.3 Filters, traps and flame arrestors . 91
11.5.4 Flow system and sample chamber . 91
11.5.5 Flow connections . 91
11.5.6 Moving parts . 91
11.5.7 Automatic sample-draw systems . 91
11.5.8 Trouble Loss-of-flow signals . 91
11.6 Readout devices . 91
11.6.1 General . 91
11.6.2 Other readouts . 91
11.7 Alarms . 92

– 6 – IEC 60079-29-2:2015 RLV  IEC 2015

11.8 Workshop calibration test and equipment Calibration . 92
11.8.1 Calibration kits and test equipment . 92
11.8.2 Conduct of workshop calibration testing Calibration procedure . 93
Annex A (normative) Measuring principles . 95
A.1 General . 95
A.2 Catalytic sensors . 97
A.2.1 General . 97
A.2.2 Common applications . 98
A.2.3 Limitations . 98
A.2.4 Interferences . 99
A.2.5 Poisoning . 99
A.3 Thermal conductivity sensors . 100
A.3.1 General . 100
A.3.2 Common applications . 100
A.3.3 Limitations . 101
A.3.4 Interferences . 101
A.3.5 Poisoning . 101
A.4 Infrared sensors . 102
A.4.1 General . 102
A.4.2 Common applications . 104
A.4.3 Limitations . 105
A.4.4 Interferences . 105
A.4.5 Poisoning . 105
A.5 Semi-conductor sensors. 105
A.5.1 General . 105
A.5.2 Common applications . 106
A.5.3 Limitations . 106
A.5.4 Interferences . 107
A.5.5 Poisoning . 107
A.6 Electrochemical sensors . 107
A.6.1 General . 107
A.6.2 Common applications . 108
A.6.3 Limitations . 108
A.6.4 Interferences . 109
A.6.5 Poisoning . 109
A.7 Flame ionization detectors (FID) . 109
A.7.1 General . 109
A.7.2 Common applications . 110
A.7.3 Limitations . 111
A.7.4 Interferences . 111
A.7.5 Poisoning . 111
A.8 Flame temperature analysers (FTA) . 111
A.8.1 General . 111
A.8.2 Common applications . 112
A.8.3 Limitations . 112
A.8.4 Interferences . 112
A.8.5 Poisoning . 112
A.9 Photo ionisation detector (PID) . 112
A.9.1 General . 112

A.9.2 Common applications . 113
A.9.3 Limitations . 113
A.9.4 Interferences . 114
A.9.5 Poisoning . 114
A.10 Paramagnetic oxygen detector . 114
A.10.1 General . 114
A.10.2 Common applications . 115
A.10.3 Limitations . 115
A.10.4 Interference . 115
A.10.5 Poisoning . 115
Annex B (informative) Environmental parameters . 116
Annex C (informative) Typical environmental and application check-list for flammable
gas detectors (for both Group I and Group II equipment) . 117
Annex D (informative) Typical instrument maintenance record for flammable gas
detectors . 119
Annex E (informative) Atmospheric visibility (applicable to open path equipment) . 121
Bibliography . 122

Figure 1 – Integral concentration over the path length. 38
Figure 2 – Average concentration over the path length . 39

Table 1 – Typical Tasks and Most Relevant Causes . 12
Table 2 – Overview of gas detection apparatus equipment with different measuring
principles . 40
Table A.1 – Overview of gas detection apparatus equipment with different measuring
principles . 96
Table B.1 – Environmental parameters . 116

– 8 – IEC 60079-29-2:2015 RLV  IEC 2015

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 29-2: Gas detectors – Selection, installation, use
and maintenance of detectors for flammable gases and oxygen

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,
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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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.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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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 60079-29-2 has been prepared by IEC technical committee 31:
Equipment for explosive atmospheres.
This second edition cancels and replaces the first edition published in 2007. This edition
constitutes a technical revision.
This edition includes the following significant changes with respect to the previous edition:
Type
Changes Clause Minor and Extension Major technical
editorial changes
changes
Addition of group 1 to scope 1 x
Addition of Open Path Gas Detection 3, 4.6, 5.4, x
6.2.3.5, 8.2,
8.6, 8.7. 8.8,
11, A4
Changed “combustible” to “flammable” Throughout x
Addition of specific applications 4.5 x
Improvements to sampling systems 6.2.3.4, 8.2.3, x
8.5, 11.2.2
NOTE The technical changes referred to include the significance of technical changes in the revised IEC
Standard, but they do not form an exhaustive list of all modifications from the previous version. More guidance may
be found by referring to the Redline Version of the standard.
Explanations:
1) Minor and editorial changes clarification
decrease of technical requirements
minor technical change
editorial corrections
These are changes which modify requirements in an editorial or a minor technical way.
They include changes of the wording to clarify technical requirements without any
technical change, or a reduction in level of existing requirement.
2) Extension addition of technical options
These are changes 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 will not have to be considered for
products in conformity with the preceding edition.
NOTE These changes represent current technological knowledge. However, these changes should not
normally have an influence on equipment already placed on the market.
3) Major technical changes addition of technical requirements
increase of technical requirements
These are changes to technical requirements (addition, increase of the level or removal)
made in a way that a product in conformity with the preceding edition will not always be
able to fulfil the requirements given in the later edition. These changes have to be
considered for products in conformity with the preceding edition.
NOTE These changes represent current technological knowledge. However, these changes should not
normally have an influence on equipment already placed on the market.

– 10 – IEC 60079-29-2:2015 RLV  IEC 2015

The text of this standard is based on the following documents:
FDIS Report on voting
31/1169/FDIS 31/1179/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60079 series, published 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.
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.

INTRODUCTION
Flammable gas detection apparatus equipment may be used whenever there is the possibility
of a hazard to life or property caused by the accumulation of a flammable gas-air mixture.
Such apparatus equipment can provide a means of reducing the hazard by detecting the
presence of a flammable gas and issuing suitable audible or visual warnings. Gas detectors
may also be used to initiate precautionary steps (for example plant shutdown, evacuation, and
operation of fire extinguishing procedures).
Apparatus Equipment may be used to monitor a gas atmosphere below the lower flammable
limit in circumstances where accumulation of gas may result in a concentration of the gas/air
mixture to potentially explosive levels. Performance requirements for gas detecting apparatus
equipment for such purposes are set out in IEC 60079-29-1 and IEC 60079-29-4. Guidance
for functional safety of fixed gas detection systems are set out in IEC 60079-29-3.
However performance capability alone cannot ensure that the use of such apparatus
equipment will properly safeguard life or property where flammable gases may be present.
The level of safety obtained depends heavily upon correct selection, installation, calibration
and periodic maintenance of the apparatus equipment, combined with knowledge of the
limitations of the detection technique required. This cannot be achieved without responsible
informed management.
An additional hazard to life is the toxicity of some gases and of the vapours of all liquids
except water. It is not generally appreciated that all flammable vapours are potentially toxic at
concentration levels which are very small fractions of their respective lower flammable limits.
Apparatus E
...

IEC 60079-29-2 ®
Edition 2.0 2015-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 29-2: Gas detectors – Selection, installation, use and maintenance of
detectors for flammable gases and oxygen

Atmosphères explosives –
Partie 29-2: Détecteurs de gaz – Sélection, installation, utilisation et maintenance
des détecteurs de gaz inflammables et d’oxygène

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
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About the IEC
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International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

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IEC 60079-29-2 ®
Edition 2.0 2015-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 29-2: Gas detectors – Selection, installation, use and maintenance of

detectors for flammable gases and oxygen

Atmosphères explosives –
Partie 29-2: Détecteurs de gaz – Sélection, installation, utilisation et maintenance

des détecteurs de gaz inflammables et d’oxygène

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-5029-7

– 2 – IEC 60079-29-2:2015  IEC 2015
CONTENTS
FOREWORD . 8
INTRODUCTION . 11
1 Scope . 13
2 Normative references . 14
3 Terms and definitions . 14
3.1 Gas properties and other physics . 14
3.2 Types of equipment . 16
3.3 Sensors and detectors . 18
3.4 Supply of gas to instruments . 19
3.5 Signals and alarms . 19
3.6 Times, checks and equipment behaviour . 20
3.7 Terms exclusive to open path equipment . 21
4 Basic information on the properties, behaviour, gases and vapours, and specific
applications of gas detection . 23
4.1 Detecting gases and vapours . 23
4.1.1 General . 23
4.1.2 Safety when monitoring for flammable gases where personnel could be
present . 24
4.2 Some common properties of gases and vapours . 25
4.3 The differences between detecting gases and vapours . 26
4.3.1 General . 26
4.3.2 Detection of gases . 26
4.3.3 Detection of vapours . 28
4.4 Oxygen deficiency. 31
4.4.1 General . 31
4.4.2 Chemical reaction of oxygen, with solid products . 31
4.4.3 Chemical reaction of oxygen, with gaseous products . 31
4.4.4 Dilution of the air by displacement by some other gas or vapour . 32
4.5 Specific applications of gas detection . 32
4.5.1 Gas detection as means of reducing risk of explosion . 32
4.5.2 Gas free work permit . 35
4.5.3 Monitoring of air inlets . 36
4.6 Specific considerations for open path detection . 36
5 Measuring principles . 37
5.1 General . 37
5.2 Catalytic sensors . 39
5.2.1 General . 39
5.2.2 Common applications . 39
5.2.3 Limitations . 39
5.2.4 Interferences . 40
5.2.5 Poisoning . 40
5.3 Thermal conductivity sensors . 40
5.3.1 General . 40
5.3.2 Common applications . 41
5.3.3 Limitations . 41
5.3.4 Interferences . 41

5.3.5 Poisoning . 41
5.4 Infrared sensors . 41
5.4.1 General . 41
5.4.2 Common applications . 41
5.4.3 Limitations . 42
5.4.4 Interferences . 42
5.4.5 Poisoning . 42
5.5 Semiconductor sensors . 42
5.5.1 General . 42
5.5.2 Common applications . 42
5.5.3 Limitations . 43
5.5.4 Interferences . 43
5.5.5 Poisoning . 43
5.6 Electrochemical sensors . 43
5.6.1 General . 43
5.6.2 Common applications . 44
5.6.3 Limitations . 44
5.6.4 Interferences . 44
5.6.5 Poisoning . 44
5.7 Flame ionization detectors (FID) . 44
5.7.1 General . 44
5.7.2 Common applications . 44
5.7.3 Limitations . 45
5.7.4 Interferences . 45
5.7.5 Poisoning . 45
5.8 Flame temperature analysers (FTA) . 45
5.8.1 General . 45
5.8.2 Common applications . 45
5.8.3 Limitations . 45
5.8.4 Interferences . 45
5.8.5 Poisoning . 46
5.9 Photo ionisation detector (PID) . 46
5.9.1 General . 46
5.9.2 Common applications . 46
5.9.3 Limitations . 46
5.9.4 Interferences . 46
5.9.5 Poisoning . 46
5.10 Paramagnetic oxygen detector . 46
5.10.1 General . 46
5.10.2 Common applications . 47
5.10.3 Limitations . 47
5.10.4 Interference . 47
5.10.5 Poisoning . 47
6 Selection of equipment . 47
6.1 General . 47
6.2 Selection criteria . 48
6.2.1 General criteria . 48
6.2.2 Gases to be detected by the equipment . 49
6.2.3 Application of fixed equipment . 50

– 4 – IEC 60079-29-2:2015  IEC 2015
6.2.4 Application of transportable and portable equipment . 53
6.3 Miscellaneous factors affecting selection of equipment . 54
6.3.1 Electromagnetic immunity . 54
6.3.2 Intended Zone(s) of use . 54
7 Behaviour of gas releases . 55
7.1 Nature of a release . 55
7.1.1 General . 55
7.1.2 Release rate of gas or vapour . 55
7.1.3 Flammable limits . 56
7.1.4 Ventilation . 56
7.1.5 Relative density of the released gas or vapour. 56
7.1.6 Temperature and/or pressure. 56
7.1.7 Other parameters to be considered . 57
7.1.8 Outdoor sites and open structures . 57
7.2 Buildings and enclosures . 57
7.2.1 General . 57
7.2.2 Unventilated buildings and enclosures . 57
7.2.3 Ventilated buildings and enclosures . 57
7.3 Environmental considerations . 59
8 Design and installation of fixed gas detection systems . 59
8.1 General . 59
8.2 Basic considerations for the installation of fixed systems . 59
8.2.1 General . 59
8.2.2 Point detection equipment and remote sensors . 60
8.2.3 Systems consisting of sampling equipment . 60
8.2.4 Open path (line of sight) equipment . 60
8.3 Location of detection points . 61
8.3.1 General . 61
8.3.2 General site considerations . 61
8.3.3 Environmental conditions . 62
8.4 Access for calibration and maintenance . 64
8.5 Additional considerations for sample lines . 65
8.6 Additional considerations for open path equipment . 65
8.7 Summary of considerations for the location of measuring points and open
paths . 66
8.8 Installation of measuring point and open path equipment . 66
8.9 Integrity and safety of fixed systems . 67
8.9.1 General . 67
8.9.2 Redundancy in fixed systems. 67
8.9.3 Protection against loss of main power supply . 67
8.10 Timing of installation during construction operations . 68
8.11 Commissioning . 68
8.11.1 Inspection . 68
8.11.2 Initial gas calibration . 69
8.11.3 Adjustment of alarm set points . 69
8.12 Operating instructions, plans and records . 69
9 Use of portable and transportable flammable gas detection equipment . 70
9.1 General . 70

9.2 Initial and periodic check procedures for portable and transportable
instrumentation . 71
9.2.1 General . 71
9.2.2 Inspection and functional checks . 71
9.2.3 Routine tests and recalibration . 72
9.2.4 Maintenance and recalibration . 73
9.3 Guidance on the use of portable and transportable equipment . 74
9.3.1 Electrical safety in hazardous atmospheres . 74
9.3.2 Safety of personnel . 74
9.3.3 Spot tests and sampling . 74
9.3.4 Sampling above liquids . 75
9.3.5 Avoidance of condensation . 75
9.3.6 Poisoning of sensors . 75
9.3.7 Changes of temperature . 75
9.3.8 Accidental damage . 75
9.3.9 Minimalist operation, the “Read and run” concept . 75
10 Training of operational personnel . 76
10.1 General . 76
10.2 General training – Basic limitations and safety . 77
10.3 Operator training . 77
10.4 Maintenance training . 78
11 Maintenance, routine procedures and general administrative control . 78
11.1 General . 78
11.2 Operational checks . 80
11.2.1 General . 80
11.2.2 Fixed systems . 80
11.2.3 Portable and transportable gas detection equipment . 80
11.3 Maintenance . 81
11.3.1 General . 81
11.3.2 Fixed equipment . 81
11.3.3 Portable and transportable gas detection equipment . 81
11.3.4 Off-site maintenance, general . 82
11.3.5 Maintenance procedures. 82
11.4 Sensors . 82
11.4.1 General . 82
11.4.2 Flame arrestor . 82
11.5 Flow systems . 83
11.5.1 General . 83
11.5.2 Inspection . 83
11.5.3 Filters, traps and flame arrestors . 83
11.5.4 Flow system and sample chamber . 83
11.5.5 Flow connections . 83
11.5.6 Moving parts . 83
11.5.7 Automatic sample-draw systems . 83
11.5.8 Loss-of-flow signals . 83
11.6 Readout devices . 83
11.6.1 General . 83
11.6.2 Other readouts . 84
11.7 Alarms . 84

– 6 – IEC 60079-29-2:2015  IEC 2015
11.8 Calibration . 84
11.8.1 Calibration kits and test equipment . 84
11.8.2 Calibration procedure . 85
Annex A (normative) Measuring principles . 87
A.1 General . 87
A.2 Catalytic sensors . 89
A.2.1 General . 89
A.2.2 Common applications . 90
A.2.3 Limitations . 90
A.2.4 Interferences . 90
A.2.5 Poisoning . 91
A.3 Thermal conductivity sensors . 92
A.3.1 General . 92
A.3.2 Common applications . 92
A.3.3 Limitations . 93
A.3.4 Interferences . 93
A.3.5 Poisoning . 93
A.4 Infrared sensors . 93
A.4.1 General . 93
A.4.2 Common applications . 95
A.4.3 Limitations . 96
A.4.4 Interferences . 96
A.4.5 Poisoning . 97
A.5 Semi-conductor sensors. 97
A.5.1 General . 97
A.5.2 Common applications . 97
A.5.3 Limitations . 97
A.5.4 Interferences . 98
A.5.5 Poisoning . 98
A.6 Electrochemical sensors . 98
A.6.1 General . 98
A.6.2 Common applications . 99
A.6.3 Limitations . 99
A.6.4 Interferences . 100
A.6.5 Poisoning . 100
A.7 Flame ionization detectors (FID) . 101
A.7.1 General . 101
A.7.2 Common applications . 102
A.7.3 Limitations . 102
A.7.4 Interferences . 102
A.7.5 Poisoning . 102
A.8 Flame temperature analysers (FTA) . 103
A.8.1 General . 103
A.8.2 Common applications . 103
A.8.3 Limitations . 103
A.8.4 Interferences . 103
A.8.5 Poisoning . 103
A.9 Photo ionisation detector (PID) . 104
A.9.1 General . 104

A.9.2 Common applications . 104
A.9.3 Limitations . 105
A.9.4 Interferences . 105
A.9.5 Poisoning . 105
A.10 Paramagnetic oxygen detector . 105
A.10.1 General . 105
A.10.2 Common applications . 106
A.10.3 Limitations . 106
A.10.4 Interference . 106
A.10.5 Poisoning . 106
Annex B (informative) Environmental parameters . 107
Annex C (informative) Typical environmental and application check-list for flammable
gas detectors (for both Group I and Group II equipment) . 108
Annex D (informative) Typical instrument maintenance record for flammable gas
detectors . 110
Annex E (informative) Atmospheric visibility . 111
Bibliography . 112

Figure 1 – Integral concentration over the path length. 37
Figure 2 – Average concentration over the path length . 37

Table 1 – Typical Tasks and Most Relevant Causes . 12
Table 2 – Overview of gas detection equipment with different measuring principles . 38
Table A.1 – Overview of gas detection equipment with different measuring principles . 88
Table B.1 – Environmental parameters . 107

– 8 – IEC 60079-29-2:2015  IEC 2015
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 29-2: Gas detectors – Selection, installation, use
and maintenance of detectors for flammable gases and oxygen

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
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agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60079-29-2 has been prepared by IEC technical committee 31:
Equipment for explosive atmospheres.
This bilingual version (2017-12) corresponds to the monolingual English version, published in
2015-03.
This second edition cancels and replaces the first edition published in 2007. This edition
constitutes a technical revision.

This edition includes the following significant changes with respect to the previous edition:
Type
Changes Clause Minor and Extension Major technical
editorial changes
changes
Addition of group 1 to scope 1 x
Addition of Open Path Gas Detection 3, 4.6, 5.4, x
6.2.3.5, 8.2,
8.6, 8.7. 8.8,
11, A4
Changed “combustible” to “flammable” Throughout x
Addition of specific applications 4.5 x
Improvements to sampling systems 6.2.3.4, 8.2.3, x
8.5, 11.2.2
NOTE The technical changes referred to include the significance of technical changes in the revised IEC
Standard, but they do not form an exhaustive list of all modifications from the previous version. More guidance may
be found by referring to the Redline Version of the standard.
Explanations:
1) Minor and editorial changes clarification
decrease of technical requirements
minor technical change
editorial corrections
These are changes which modify requirements in an editorial or a minor technical way.
They include changes of the wording to clarify technical requirements without any
technical change, or a reduction in level of existing requirement.
2) Extension addition of technical options
These are changes 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 will not have to be considered for
products in conformity with the preceding edition.
NOTE These changes represent current technological knowledge. However, these changes should not
normally have an influence on equipment already placed on the market.
3) Major technical changes addition of technical requirements
increase of technical requirements
These are changes to technical requirements (addition, increase of the level or removal)
made in a way that a product in conformity with the preceding edition will not always be
able to fulfil the requirements given in the later edition. These changes have to be
considered for products in conformity with the preceding edition.
NOTE These changes represent current technological knowledge. However, these changes should not
normally have an influence on equipment already placed on the market.
The text of this standard is based on the following documents:
FDIS Report on vo
...