IEC 62990-2:2021
(Main)Workplace atmospheres — Part 2: Gas detectors — Selection, installation, use and maintenance of detectors for toxic gases and vapours
Workplace atmospheres — Part 2: Gas detectors — Selection, installation, use and maintenance of detectors for toxic gases and vapours
IEC 62990-2:2021 gives guidance on the selection, installation, use and maintenance of electrical equipment used for the measurement of toxic gases and vapours in workplace atmospheres. The primary purpose of such equipment is to ensure safety of personnel and property by providing an indication of the concentration of a toxic gas or vapour and warning of its presence. This document is applicable to equipment whose purpose is to provide an indication, alarm or other output function to give a warning of the presence of a toxic gas or vapour in the atmosphere and in some cases to initiate automatic or manual protective actions. It is applicable to equipment in which the sensor automatically generates an electrical signal when gas is present. For the purposes of this document, equipment includes: a) fixed equipment; b) transportable equipment, and c) portable equipment. This document is intended to cover equipment defined within IEC 62990-1, but can provide useful information for equipment not covered by that document.
Atmosphères des lieux de travail — Partie 2: Détecteurs de gaz — Sélection, installation, utilisation et maintenance des détecteurs de gaz et de vapeurs toxiques
IEC 62990-2:2021 donne des recommandations pour la sélection, l’installation, l’utilisation et la maintenance du matériel électrique utilisé pour le mesurage des gaz et des vapeurs toxiques dans les atmosphères des lieux de travail. Le principal objectif de ce type de matériel est d’assurer la sécurité des personnes et des biens en fournissant une indication de la concentration d’un gaz ou d’une vapeur toxique et en avertissant de sa présence. Le présent document s’applique aux matériels dont l’objectif principal est de donner une indication, une alarme ou une autre fonction de sortie pour avertir de la présence d’un gaz ou d’une vapeur toxique dans l’atmosphère et, dans certains cas, de déclencher des actions protectrices automatiques ou manuelles. Il s’applique aux matériels dont le capteur génère automatiquement un signal électrique en présence de gaz. Pour les besoins du présent document, les matériels comprennent: a) le matériel fixe; b) le matériel transportable; et c) le matériel portable. Le présent document est destiné à couvrir les matériels définis dans l’IEC 62990-1, mais peut fournir des informations utiles pour des matériels non couverts par ce document.
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IEC 62990-2
Edition 1.0 2021-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Workplace atmospheres –
Part 2: Gas detectors – Selection, installation, use and maintenance of detectors
for toxic gases and vapours
Atmosphères des lieux de travail –
Partie 2: Détecteurs de gaz – Sélection, installation, utilisation et maintenance
des détecteurs de gaz et de vapeurs toxiques
IEC 62990-2:2021-06(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 62990-2
Edition 1.0 2021-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Workplace atmospheres –
Part 2: Gas detectors – Selection, installation, use and maintenance of detectors
for toxic gases and vapours
Atmosphères des lieux de travail –
Partie 2: Détecteurs de gaz – Sélection, installation, utilisation et maintenance
des détecteurs de gaz et de vapeurs toxiques
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-1048-5
Warning! Make sure that you obtained this publication from an authorized distributor.
Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.
---------------------- Page: 3 ----------------------
– 2 – IEC 62990-2:2021 © IEC 2021
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Properties and detection of toxic gases and vapours . 13
4.1 Properties and detection . 13
4.2 The difference between detecting gases and vapours . 14
4.3 Effects of water vapour on detection . 17
4.4 Effects of temperature and pressure on detection . 17
4.5 Effects of corrosion on detection . 17
4.6 Detection by oxygen deficiency measurement . 17
5 Measurement tasks . 18
5.1 General . 18
5.2 Exposure measurement (health monitoring) . 18
5.3 General gas detection (safety monitoring) . 19
6 Selection of equipment . 20
6.1 General . 20
6.2 Performance and electrical tests . 21
6.3 Indication range, measuring range and uncertainty of measurement . 21
6.4 Selectivity requirements . 22
6.5 The influence of environmental conditions . 23
6.6 The influence of electromagnetic interference . 23
6.7 Time of response and time of recovery . 24
6.8 Time to alarm . 25
6.9 Data logging . 25
6.10 Instruction manual . 26
7 Design and installation of fixed toxic gas detection equipment . 26
7.1 General . 26
7.2 Basic considerations for the installation of fixed systems . 27
7.3 Location of detection points . 28
7.4 Access for calibration and maintenance . 33
7.5 Additional considerations for sample lines . 33
7.6 Summary of considerations for the location of sensors or sampling points . 34
7.7 Installation of sensors . 35
7.8 Integrity and safety of fixed systems . 35
7.9 Commissioning . 36
7.10 Operating instructions, plans and records . 37
8 Operation of toxic gas detection equipment . 38
8.1 Alarm setting. 38
8.2 Operation of portable equipment . 39
8.3 Operation of transportable and fixed equipment . 43
8.4 Sample lines and sampling probes . 45
8.5 Accessories . 45
9 Maintenance and calibration . 46
9.1 General . 46
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IEC 62990-2:2021 © IEC 2021 – 3 –
9.2 Sensor . 46
9.3 Flow systems of aspirated equipment. 46
9.4 Readout devices . 47
9.5 Alarms . 47
9.6 Maintenance . 47
9.7 Calibration . 48
9.8 Operation test . 49
9.9 Records . 50
10 Training . 50
10.1 General . 50
10.2 Operator training . 50
10.3 Maintenance and calibration training . 51
Annex A (informative) Commonly used measurement principles . 52
A.1 General . 52
A.2 Chemiluminescence . 52
A.3 Colorimetry . 53
A.4 Electrochemical . 54
A.5 Flame-ionization . 55
A.6 Gas chromatography . 55
A.7 Infrared photometry . 56
A.8 Ion mobility spectrometry . 57
A.9 Mass spectrometry . 58
A.10 Photo-ionization . 59
A.11 Semiconductor . 60
A.12 Ultra-violet/visible photometry . 61
Bibliography . 62
Figure 1 – Relationship between indication range and measuring range (See 6.3.1) . 11
Figure 2 – Example of zero uncertainty . 11
Figure 3 – Example of warm-up time in clean air . 12
Figure 4 – Relationship between indication range and measuring range . 22
Figure 5 – Gas response curves for test gas volume fractions of 40 ppm and 100 ppm . 24
Figure 6 – Time to alarm at 25 ppm set point for test gas volume fractions of 40 ppm
and 100 ppm . 25
Table A.1 – Chemiluminescence . 52
Table A.2 – Colorimetry . 53
Table A.3 – Electrochemical . 54
Table A.4 – Flame-ionization . 55
Table A.5 – Infrared photometry . 56
Table A.6 – Ion mobility spectrometry . 57
Table A.7 – Mass spectrometry . 58
Table A.8 – Photo-ionization (PID) . 59
Table A.9 – Semiconductor . 60
Table A.10 – Ultra-violet/visible photometry . 61
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– 4 – IEC 62990-2:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WORKPLACE ATMOSPHERES –
Part 2: Gas detectors –
Selection, installation, use and maintenance
of detectors for toxic gases and vapours
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
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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.
International Standard IEC 62990-2 has been prepared IEC technical committee 31: Equipment
for explosive atmospheres and ISO technical committee 146: Air quality, sub-committee 2:
Workplace atmospheres.
It is published as a double logo standard.
The text of this International Standard is based on the following documents:
FDIS Report on voting
31/1566/FDIS 31/1568/RVD
Full information on the voting for the approval of this International Standard can be found in the
report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
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IEC 62990-2:2021 © IEC 2021 – 5 –
A list of all parts in the IEC 62990, published under the general title Workplace atmospheres,
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document 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.
---------------------- Page: 7 ----------------------
– 6 – IEC 62990-2:2021 © IEC 2021
INTRODUCTION
Toxic gas detection equipment can be used whenever there is the possibility of a hazard to life
or adverse health effects caused by the accumulation of a toxic gas or vapour. Such equipment
can provide a means of reducing the exposure to the hazard by detecting the presence of a
toxic gas or vapour and issuing suitable audible or visual warnings. Gas detectors can also be
used to initiate precautionary steps (for example, plant shutdown and evacuation).
Performance requirements for gas detection equipment for workplace atmospheres are set out
in IEC 62990 series standards.
However performance capability alone cannot ensure that the use of such equipment will
properly safeguard life and health where toxic gases and vapours might be present. The level
of safety obtained depends heavily upon correct selection, installation, calibration and periodic
maintenance of the equipment, combined with knowledge of the limitations of the detection
technique required. This cannot be achieved without responsible informed management.
This document has been specifically written to cover all the functions necessary from selection
to ongoing maintenance for a successful gas detection operation.
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IEC 62990-2:2021 © IEC 2021 – 7 –
WORKPLACE ATMOSPHERES –
Part 2: Gas detectors –
Selection, installation, use and maintenance
of detectors for toxic gases and vapours
1 Scope
This document gives guidance on the selection, installation, use and maintenance of electrical
equipment used for the measurement of toxic gases and vapours in workplace atmospheres.
The primary purpose of such equipment is to ensure safety of personnel and property by
providing an indication of the concentration of a toxic gas or vapour and warning of its presence.
This document is applicable to equipment whose purpose is to provide an indication, alarm or
other output function to give a warning of the presence of a toxic gas or vapour in the
atmosphere and in some cases to initiate automatic or manual protective actions. It is applicable
to equipment in which the sensor automatically generates an electrical signal when gas is
present.
For the purposes of this document, equipment includes:
a) fixed equipment;
b) transportable equipment, and
c) portable equipment.
This document is intended to cover equipment defined within IEC 62990-1, but can provide
useful information for equipment not covered by that document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60079-29-2, Explosive atmospheres – Part 29-2: Gas detectors – Selection, installation,
use and maintenance of detectors for flammable gases and oxygen
IEC 62990-1, Workplace atmospheres – Part 1: Gas detectors – Performance requirements of
detectors for toxic gases
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62990-1 and the
following apply.
NOTE 1 Certain definitions within IEC 62990-1 are repeated below for the convenience of the reader.
---------------------- Page: 9 ----------------------
– 8 – IEC 62990-2:2021 © IEC 2021
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
NOTE 2 Additional definitions applicable to explosive atmospheres can be found in Chapter 426 of the International
Electrotechnical Vocabulary (IEC 60050-426).
3.1
toxic gas
gas or vapour that can be harmful to human health and/or the performance of persons due to
its physical or physico-chemical properties
Note 1 to entry: For the purpose of this document, the term “toxic gas” includes “toxic vapours”.
3.2
interfering gas
any gas other than the gas to be detected, including water vapour, which affects the indication
3.3
clean air
air that is free of gases or vapours to which the sensor is sensitive or which influence the
performance of the sensor
3.4
zero gas
gas recommended by the manufacturer, which is free of toxic gases and interfering and
contaminating substances, the purpose of which is calibration or adjustment of the equipment
zero
3.5
volume fraction
quotient of the volume of a specified component and the sum of the volumes of all components
of a gas mixture before mixing, all volumes referring to the pressure and the temperature of the
gas mixture
Note 1 to entry: The volume fraction and volume concentration take the same value if, at the same state conditions,
the sum of the component volumes before mixing and the volume of the mixture are equal. However, because the
mixing of two or more gases at the same state conditions is usually accompanied by a slight contraction or, less
frequently, a slight expansion, this is not generally the case.
3.6
occupational exposure limit value
OELV
limit of the time-weighted average of the concentration of a chemical agent in the air within the
breathing zone of a worker in relation to a specified reference period
Note 1 to entry: The term “limit value” is often used as a synonym for “occupational exposure limit value”, but the
term “occupational exposure limit value” is preferred because there is more than one limit value (e.g., biological limit
value and occupational exposure limit value).
Note 2 to entry: Occupational exposure limit values (OELVs) are often set for reference periods of 8 h, but can also
be set for shorter periods or concentration excursions.
[SOURCE: ISO 18158:2016, 2.1.5.4, modified (Note 2 to entry is shortened)]
3.7
exposure (by inhalation)
situation in which a chemical agent is present in air that is inhaled by a person
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IEC 62990-2:2021 © IEC 2021 – 9 –
3.8
time weighted average concentration
TWA concentration
concentration of gas in air averaged over a reference period
3.9
fixed equipment
equipment fastened to a support, or otherwise secured in a specific location, when energized
3.10
transportable equipment
equipment not intended to be carried by a person during operation, nor intended for fixed
installation
3.11
portable equipment
equipment intended to be carried by a person during its operation
Note 1 to entry: Portable equipment is battery powered and includes, but is not limited to;
a) hand-held equipment, typically less than 1 kg, which requires use of only one hand to operate,
b) personal monitors, similar in size and mass to the hand-held equipment, that are continuously operating while
they are attached to the user, and,
c) larger equipment that can be operated by the user while it is carried either by hand, by a shoulder strap or
carrying harness and which might or might not have a hand directed probe.
3.12
aspirated equipment
equipment that samples the atmosphere by drawing it to the sensor
Note 1 to entry: A hand operated or electric pump is often used to draw gas to the sensor.
3.13
alarm-only equipment
equipment with an alarm but not having an indication of measured value
3.14
sensing element
part of the sensor which is sensitive to the gas or vapour to be measured
3.15
sensor
assembly in which the sensing element is housed and that can also contain associated circuit
components
3.16
remote sensor
sensor which is installed separately, but is connected to a gas detection control unit, gas
detection transmitter, or transportable or portable equipment
3.17
gas detection transmitter
fixed gas detection equipment that provides a conditione
...
IEC 62990-2
Edition 1.0 2021-06
INTERNATIONAL
STANDARD
colour
inside
Workplace atmospheres –
Part 2: Gas detectors – Selection, installation, use and maintenance of detectors
for toxic gases and vapours
IEC 62990-2:2021-06(en)
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
Copyright © 2021 IEC, Geneva, Switzerland
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
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.
IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
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 corrigendum or an amendment might have been published.
IEC publications search - webstore.iec.ch/advsearchform IEC online collection - oc.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews. With a subscription you will always
committee, …). It also gives information on projects, replaced have access to up to date content tailored to your needs.
and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 000 terminological entries in English
details all new publications released. Available online and
and French, with equivalent terms in 18 additional languages.
once a month by email.
Also known as the International Electrotechnical Vocabulary
(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc
If you wish to give us your feedback on this publication or
need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
---------------------- Page: 2 ----------------------
IEC 62990-2
Edition 1.0 2021-06
INTERNATIONAL
STANDARD
colour
inside
Workplace atmospheres –
Part 2: Gas detectors – Selection, installation, use and maintenance of detectors
for toxic gases and vapours
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.260.20 ISBN 978-2-8322-9746-9
Warning! Make sure that you obtained this publication from an authorized distributor.
---------------------- Page: 3 ----------------------
– 2 – IEC 62990-2:2021 © IEC 2021
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Properties and detection of toxic gases and vapours . 13
4.1 Properties and detection . 13
4.2 The difference between detecting gases and vapours . 14
4.3 Effects of water vapour on detection . 17
4.4 Effects of temperature and pressure on detection . 17
4.5 Effects of corrosion on detection . 17
4.6 Detection by oxygen deficiency measurement . 17
5 Measurement tasks . 18
5.1 General . 18
5.2 Exposure measurement (health monitoring) . 18
5.3 General gas detection (safety monitoring) . 19
6 Selection of equipment . 20
6.1 General . 20
6.2 Performance and electrical tests . 21
6.3 Indication range, measuring range and uncertainty of measurement . 21
6.4 Selectivity requirements . 22
6.5 The influence of environmental conditions . 23
6.6 The influence of electromagnetic interference . 23
6.7 Time of response and time of recovery . 24
6.8 Time to alarm . 25
6.9 Data logging . 25
6.10 Instruction manual . 26
7 Design and installation of fixed toxic gas detection equipment . 26
7.1 General . 26
7.2 Basic considerations for the installation of fixed systems . 27
7.3 Location of detection points . 28
7.4 Access for calibration and maintenance . 33
7.5 Additional considerations for sample lines . 33
7.6 Summary of considerations for the location of sensors or sampling points . 34
7.7 Installation of sensors . 35
7.8 Integrity and safety of fixed systems . 35
7.9 Commissioning . 36
7.10 Operating instructions, plans and records . 37
8 Operation of toxic gas detection equipment . 38
8.1 Alarm setting. 38
8.2 Operation of portable equipment . 39
8.3 Operation of transportable and fixed equipment . 43
8.4 Sample lines and sampling probes . 45
8.5 Accessories . 45
9 Maintenance and calibration . 46
9.1 General . 46
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IEC 62990-2:2021 © IEC 2021 – 3 –
9.2 Sensor . 46
9.3 Flow systems of aspirated equipment. 46
9.4 Readout devices . 47
9.5 Alarms . 47
9.6 Maintenance . 47
9.7 Calibration . 48
9.8 Operation test . 49
9.9 Records . 50
10 Training . 50
10.1 General . 50
10.2 Operator training . 50
10.3 Maintenance and calibration training . 51
Annex A (informative) Commonly used measurement principles . 52
A.1 General . 52
A.2 Chemiluminescence . 52
A.3 Colorimetry . 53
A.4 Electrochemical . 54
A.5 Flame-ionization . 55
A.6 Gas chromatography . 55
A.7 Infrared photometry . 56
A.8 Ion mobility spectrometry . 57
A.9 Mass spectrometry . 58
A.10 Photo-ionization . 59
A.11 Semiconductor . 60
A.12 Ultra-violet/visible photometry . 61
Bibliography . 62
Figure 1 – Relationship between indication range and measuring range (See 6.3.1) . 11
Figure 2 – Example of zero uncertainty . 11
Figure 3 – Example of warm-up time in clean air . 12
Figure 4 – Relationship between indication range and measuring range . 22
Figure 5 – Gas response curves for test gas volume fractions of 40 ppm and 100 ppm . 24
Figure 6 – Time to alarm at 25 ppm set point for test gas volume fractions of 40 ppm
and 100 ppm . 25
Table A.1 – Chemiluminescence . 52
Table A.2 – Colorimetry . 53
Table A.3 – Electrochemical . 54
Table A.4 – Flame-ionization . 55
Table A.5 – Infrared photometry . 56
Table A.6 – Ion mobility spectrometry . 57
Table A.7 – Mass spectrometry . 58
Table A.8 – Photo-ionization (PID) . 59
Table A.9 – Semiconductor . 60
Table A.10 – Ultra-violet/visible photometry . 61
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– 4 – IEC 62990-2:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WORKPLACE ATMOSPHERES –
Part 2: Gas detectors –
Selection, installation, use and maintenance
of detectors for toxic gases and vapours
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62990-2 has been prepared IEC technical committee 31: Equipment
for explosive atmospheres and ISO technical committee 146: Air quality, sub-committee 2:
Workplace atmospheres.
It is published as a double logo standard.
The text of this International Standard is based on the following documents:
FDIS Report on voting
31/1566/FDIS 31/1568/RVD
Full information on the voting for the approval of this International Standard can be found in the
report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
---------------------- Page: 6 ----------------------
IEC 62990-2:2021 © IEC 2021 – 5 –
A list of all parts in the IEC 62990, published under the general title Workplace atmospheres,
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document 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.
---------------------- Page: 7 ----------------------
– 6 – IEC 62990-2:2021 © IEC 2021
INTRODUCTION
Toxic gas detection equipment can be used whenever there is the possibility of a hazard to life
or adverse health effects caused by the accumulation of a toxic gas or vapour. Such equipment
can provide a means of reducing the exposure to the hazard by detecting the presence of a
toxic gas or vapour and issuing suitable audible or visual warnings. Gas detectors can also be
used to initiate precautionary steps (for example, plant shutdown and evacuation).
Performance requirements for gas detection equipment for workplace atmospheres are set out
in IEC 62990 series standards.
However performance capability alone cannot ensure that the use of such equipment will
properly safeguard life and health where toxic gases and vapours might be present. The level
of safety obtained depends heavily upon correct selection, installation, calibration and periodic
maintenance of the equipment, combined with knowledge of the limitations of the detection
technique required. This cannot be achieved without responsible informed management.
This document has been specifically written to cover all the functions necessary from selection
to ongoing maintenance for a successful gas detection operation.
---------------------- Page: 8 ----------------------
IEC 62990-2:2021 © IEC 2021 – 7 –
WORKPLACE ATMOSPHERES –
Part 2: Gas detectors –
Selection, installation, use and maintenance
of detectors for toxic gases and vapours
1 Scope
This document gives guidance on the selection, installation, use and maintenance of electrical
equipment used for the measurement of toxic gases and vapours in workplace atmospheres.
The primary purpose of such equipment is to ensure safety of personnel and property by
providing an indication of the concentration of a toxic gas or vapour and warning of its presence.
This document is applicable to equipment whose purpose is to provide an indication, alarm or
other output function to give a warning of the presence of a toxic gas or vapour in the
atmosphere and in some cases to initiate automatic or manual protective actions. It is applicable
to equipment in which the sensor automatically generates an electrical signal when gas is
present.
For the purposes of this document, equipment includes:
a) fixed equipment;
b) transportable equipment, and
c) portable equipment.
This document is intended to cover equipment defined within IEC 62990-1, but can provide
useful information for equipment not covered by that document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60079-29-2, Explosive atmospheres – Part 29-2: Gas detectors – Selection, installation,
use and maintenance of detectors for flammable gases and oxygen
IEC 62990-1, Workplace atmospheres – Part 1: Gas detectors – Performance requirements of
detectors for toxic gases
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62990-1 and the
following apply.
NOTE 1 Certain definitions within IEC 62990-1 are repeated below for the convenience of the reader.
---------------------- Page: 9 ----------------------
– 8 – IEC 62990-2:2021 © IEC 2021
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
NOTE 2 Additional definitions applicable to explosive atmospheres can be found in Chapter 426 of the International
Electrotechnical Vocabulary (IEC 60050-426).
3.1
toxic gas
gas or vapour that can be harmful to human health and/or the performance of persons due to
its physical or physico-chemical properties
Note 1 to entry: For the purpose of this document, the term “toxic gas” includes “toxic vapours”.
3.2
interfering gas
any gas other than the gas to be detected, including water vapour, which affects the indication
3.3
clean air
air that is free of gases or vapours to which the sensor is sensitive or which influence the
performance of the sensor
3.4
zero gas
gas recommended by the manufacturer, which is free of toxic gases and interfering and
contaminating substances, the purpose of which is calibration or adjustment of the equipment
zero
3.5
volume fraction
quotient of the volume of a specified component and the sum of the volumes of all components
of a gas mixture before mixing, all volumes referring to the pressure and the temperature of the
gas mixture
Note 1 to entry: The volume fraction and volume concentration take the same value if, at the same state conditions,
the sum of the component volumes before mixing and the volume of the mixture are equal. However, because the
mixing of two or more gases at the same state conditions is usually accompanied by a slight contraction or, less
frequently, a slight expansion, this is not generally the case.
3.6
occupational exposure limit value
OELV
limit of the time-weighted average of the concentration of a chemical agent in the air within the
breathing zone of a worker in relation to a specified reference period
Note 1 to entry: The term “limit value” is often used as a synonym for “occupational exposure limit value”, but the
term “occupational exposure limit value” is preferred because there is more than one limit value (e.g., biological limit
value and occupational exposure limit value).
Note 2 to entry: Occupational exposure limit values (OELVs) are often set for reference periods of 8 h, but can also
be set for shorter periods or concentration excursions.
[SOURCE: ISO 18158:2016, 2.1.5.4, modified (Note 2 to entry is shortened)]
3.7
exposure (by inhalation)
situation in which a chemical agent is present in air that is inhaled by a person
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IEC 62990-2:2021 © IEC 2021 – 9 –
3.8
time weighted average concentration
TWA concentration
concentration of gas in air averaged over a reference period
3.9
fixed equipment
equipment fastened to a support, or otherwise secured in a specific location, when energized
3.10
transportable equipment
equipment not intended to be carried by a person during operation, nor intended for fixed
installation
3.11
portable equipment
equipment intended to be carried by a person during its operation
Note 1 to entry: Portable equipment is battery powered and includes, but is not limited to;
a) hand-held equipment, typically less than 1 kg, which requires use of only one hand to operate,
b) personal monitors, similar in size and mass to the hand-held equipment, that are continuously operating while
they are attached to the user, and,
c) larger equipment that can be operated by the user while it is carried either by hand, by a shoulder strap or
carrying harness and which might or might not have a hand directed probe.
3.12
aspirated equipment
equipment that samples the atmosphere by drawing it to the sensor
Note 1 to entry: A hand operated or electric pump is often used to draw gas to the sensor.
3.13
alarm-only equipment
equipment with an alarm but not having an indication of measured value
3.14
sensing element
part of the sensor which is sensitive to the gas or vapour to be measured
3.15
sensor
assembly in which the sensing element is housed and that can also contain associated circuit
components
3.16
remote sensor
sensor which is installed separately, but is connected to a gas detection control unit, gas
detection transmitter, or transportable or portable equipment
3.17
gas detection transmitter
fixed gas detection equipment that provides a conditioned electronic signal or output indication
to a generally accepted industry standard (such as 4 to 20 mA), intended to be utilized with
separate gas detection control units or signal processing data acquisition, central monitoring
and similar systems, which typically process information from various locations and sources
including, but not limited to gas detection equipment
---------------------- Page: 11 ----------------------
– 10 – IEC 62990-2:2021 © IEC 2021
3.18
separate gas detection control unit
equipment intended to provide display indication, alarm functions, output contacts or alarm
signal outputs or any combination when operated with gas detection transmitters(s)
3.19
alarm set point
setting of the equipment at which the measured concentration will cause the equipment to
initiate an indication, alarm or other output function
3.20
fault signal
audible, visible or other type of output, different from the alarm signal, permitting, directly or
indirectly, a warning or indication that the equipment is not working satisfactorily
3.21
sample line
means by which the gas being sampled is conveyed to the sensor
Note 1 to entry: Accessories such as filter or water trap are often included in the sample line.
3.22
sampling probe
separate accessory sample line which is optionally attached to the equipment
Note 1 to entry: It is usually short (for example in the order of 1 m) and rigid, although it can be telescopic. In some
cases it is connected by a flexible tube to the equipment.
3.23
field calibration kit
means of presenting test gas to the equipment for the purpose of calibrating, adjusting or
verifying the operation of the equipment
Note 1 to entry: The field calibration kit can be used for verifying the operation of the alarms if the concentration of
the test gas is above the alarm set-point.
Note 2 to entry: A mask for calibration and test is an example of a field calibration kit.
3.24
zero indication
indication given by an equipment when exposed to zero gas in normal operating conditions
3.25
indication range
range of measured values of gas concentration over which the equipment is capable of
indicating (see Figure 1)
3.26
lower limit of indication
smallest measured value within the indication range (see Figure 1)
3.27
upper limit of indication
largest measured value within the indication range (see Figure 1)
3.28
measuring range
range of measured values of gas concentration over which the accuracy of the equipment lies
within specified limits (see Figure 1)
---------------------- Page: 12 ----------------------
IEC 62990-2:2021 © IEC 2021 – 11 –
3.29
lower limit of measurement
smallest measured value within the measuring range (see Figure 1)
3.30
upper limit of measurement
largest measured va
...
FINAL
INTERNATIONAL IEC/FDIS
DRAFT
STANDARD 62990-2
ISO/TC 146/SC 2
Workplace atmospheres —
Secretariat: ANSI
Voting begins on:
Part 2:
2021-02-12
Gas detectors — Selection,
Voting terminates on:
installation, use and maintenance of
2021-04-09
detectors for toxic gases and vapours
Air des lieux de travail —
Partie 2: Détecteurs de gaz — Sélection, installation, utilisation et
maintenance des détecteurs de gaz et de vapeurs toxiques
This draft is submitted to a parallel vote in ISO and in IEC.
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
IEC/FDIS 62990-2:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
©
NATIONAL REGULATIONS. IEC 2021
---------------------- Page: 1 ----------------------
– 2 – IEC FDIS 62990-2 IEC 2021
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Properties and detection of toxic gases and vapours . 13
4.1 Properties and detection . 13
4.2 The difference between detecting gases and vapours . 15
4.3 Effects of water vapour on detection . 17
4.4 Effects of temperature and pressure on detection . 17
4.5 Effects of corrosion on detection . 18
4.6 Detection by oxygen deficiency measurement . 18
5 Measurement tasks . 18
5.1 General . 18
5.2 Exposure measurement (health monitoring) . 19
5.3 General gas detection (safety monitoring) . 20
6 Selection of equipment . 20
6.1 General . 20
6.2 Performance and electrical tests . 21
6.3 Indication range, measuring range and uncertainty of measurement . 22
6.4 Selectivity requirements . 23
6.5 The influence of environmental conditions . 23
6.6 The influence of electromagnetic interference . 24
6.7 Time of response and time of recovery . 24
6.8 Time to alarm . 25
6.9 Data logging . 26
6.10 Instruction manual . 26
7 Design and installation of fixed toxic gas detection equipment . 27
7.1 General . 27
7.2 Basic considerations for the installation of fixed systems . 27
7.3 Location of detection points . 28
7.4 Access for calibration and maintenance . 33
7.5 Additional considerations for sample lines . 34
7.6 Summary of considerations for the location of sensors or sampling points . 34
7.7 Installation of sensors . 35
7.8 Integrity and safety of fixed systems . 36
7.9 Commissioning . 37
7.10 Operating instructions, plans and records . 38
8 Operation of toxic gas detection equipment . 39
8.1 Alarm setting. 39
8.2 Operation of portable equipment . 40
8.3 Operation of transportable and fixed equipment . 44
8.4 Sample lines and sampling probes . 46
8.5 Accessories . 46
9 Maintenance and calibration . 47
9.1 General . 47
---------------------- Page: 2 ----------------------
IEC FDIS 62990-2 IEC 2021 – 3 –
9.2 Sensor . 47
9.3 Flow systems of aspirated equipment. 47
9.4 Readout devices . 48
9.5 Alarms . 48
9.6 Maintenance . 48
9.7 Calibration . 49
9.8 Operation test . 50
9.9 Records . 51
10 Training . 51
10.1 General . 51
10.2 Operator training . 51
10.3 Maintenance and calibration training . 52
Annex A (informative) Commonly used measurement principles . 53
A.1 General . 53
A.2 Chemiluminescence . 53
A.3 Colorimetry . 54
A.4 Electrochemical . 55
A.5 Flame-ionization . 56
A.6 Gas chromatography . 56
A.7 Infrared photometry . 57
A.8 Ion mobility spectrometry . 58
A.9 Mass spectrometry . 59
A.10 Photo-ionization . 60
A.11 Semiconductor . 61
A.12 Ultra-violet/visible photometry . 62
Bibliography . 63
Figure 1 – Relationship between indication range and measuring range (See 6.3.1) . 11
Figure 2 – Example of zero uncertainty . 11
Figure 3 – Example of warm-up time in clean air . 13
Figure 4 – Relationship between indication range and measuring range . 22
Figure 5 – Gas response curves for test gas volume fractions of 40 ppm and 100 ppm . 24
Figure 6 – Time to alarm at 25 ppm set point for test gas volume fractions of 40 ppm
and 100 ppm . 25
Table A.1 – Chemiluminescence . 53
Table A.2 – Colorimetry . 54
Table A.3 – Electrochemical . 55
Table A.4 – Flame-ionization . 56
Table A.5 – Infrared photometry . 57
Table A.6 – Ion mobility spectrometry . 58
Table A.7 – Mass spectrometry . 59
Table A.8 – Photo-ionization (PID) . 60
Table A.9 – Semiconductor . 61
Table A.10 – Ultra-violet/visible photometry . 62
---------------------- Page: 3 ----------------------
– 4 – IEC FDIS 62990-2 IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WORKPLACE ATMOSPHERES –
Part 2: Gas detectors –
Selection, installation, use and maintenance
of detectors for toxic gases and vapours
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62990-2 has been prepared IEC technical committee 31: Equipment
for explosive atmospheres and ISO technical committee 146: Air quality, sub-committee 2:
Workplace atmospheres.
The text of this International Standard is based on the following documents:
FDIS Report on voting
31/XX/FDIS 31/XX/RVD
Full information on the voting for the approval of this International Standard can be found in the
report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
---------------------- Page: 4 ----------------------
IEC FDIS 62990-2 IEC 2021 – 5 –
A list of all parts in the IEC 62990, published under the general title Workplace atmospheres,
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document 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.
---------------------- Page: 5 ----------------------
– 6 – IEC FDIS 62990-2 IEC 2021
INTRODUCTION
Toxic gas detection equipment can be used whenever there is the possibility of a hazard to life
or adverse health effects caused by the accumulation of a toxic gas or vapour. Such equipment
can provide a means of reducing the exposure to the hazard by detecting the presence of a
toxic gas or vapour and issuing suitable audible or visual warnings. Gas detectors can also be
used to initiate precautionary steps (for example, plant shutdown and evacuation).
Performance requirements for gas detection equipment for workplace atmospheres are set out
in IEC 62990 series standards.
However performance capability alone cannot ensure that the use of such equipment will
properly safeguard life and health where toxic gases and vapours might be present. The level
of safety obtained depends heavily upon correct selection, installation, calibration and periodic
maintenance of the equipment, combined with knowledge of the limitations of the detection
technique required. This cannot be achieved without responsible informed management.
This document has been specifically written to cover all the functions necessary from selection
to ongoing maintenance for a successful gas detection operation.
---------------------- Page: 6 ----------------------
IEC FDIS 62990-2 IEC 2021 – 7 –
WORKPLACE ATMOSPHERES –
Part 2: Gas detectors –
Selection, installation, use and maintenance
of detectors for toxic gases and vapours
1 Scope
This document gives guidance on the selection, installation, use and maintenance of electrical
equipment used for the measurement of toxic gases and vapours in workplace atmospheres.
The primary purpose of such equipment is to ensure safety of personnel and property by
providing an indication of the concentration of a toxic gas or vapour and warning of its presence.
This document is applicable to equipment whose purpose is to provide an indication, alarm or
other output function to give a warning of the presence of a toxic gas or vapour in the
atmosphere and in some cases to initiate automatic or manual protective actions. It is applicable
to equipment in which the sensor automatically generates an electrical signal when gas is
present.
For the purposes of this document, equipment includes:
a) fixed equipment;
b) transportable equipment, and
c) portable equipment.
This document is intended to cover equipment defined within IEC 62990-1, but can provide
useful information for equipment not covered by that document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60079-29-2, Explosive atmospheres – Part 29-2: Gas detectors – Selection, installation,
use and maintenance of detectors for flammable gases and oxygen
IEC 62990-1, Workplace atmospheres – Part 1: Gas detectors – Performance requirements of
detectors for toxic gases
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62990-1 and the
following apply.
NOTE 1 Certain definitions within IEC 62990-1 are repeated below for the convenience of the reader.
---------------------- Page: 7 ----------------------
– 8 – IEC FDIS 62990-2 IEC 2021
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
NOTE 2 Additional definitions applicable to explosive atmospheres can be found in Chapter 426 of the International
Electrotechnical Vocabulary (IEC 60050-426).
3.1
toxic gas
gas or vapour that can be harmful to human health and/or the performance of persons due to
its physical or physico-chemical properties
Note 1 to entry: For the purpose of this document, the term “toxic gas” includes “toxic vapours”.
3.2
interfering gas
any gas other than the gas to be detected, including water vapour, which affects the indication
3.3
clean air
air that is free of gases or vapours to which the sensor is sensitive or which influence the
performance of the sensor
3.4
zero gas
gas recommended by the manufacturer, which is free of toxic gases and interfering and
contaminating substances, the purpose of which is calibration or adjustment of the equipment
zero
3.5
volume fraction
quotient of the volume of a specified component and the sum of the volumes of all components
of a gas mixture before mixing, all volumes referring to the pressure and the temperature of the
gas mixture
Note 1 to entry: The volume fraction and volume concentration take the same value if, at the same state conditions,
the sum of the component volumes before mixing and the volume of the mixture are equal. However, because the
mixing of two or more gases at the same state conditions is usually accompanied by a slight contraction or, less
frequently, a slight expansion, this is not generally the case.
3.6
occupational exposure limit value
OELV
limit of the time-weighted average of the concentration of a chemical agent in the air within the
breathing zone of a worker in relation to a specified reference period
Note 1 to entry: The term “limit value” is often used as a synonym for “occupational exposure limit value”, but the
term “occupational exposure limit value” is preferred because there is more than one limit value (e.g., biological limit
value and occupational exposure limit value).
Note 2 to entry: Occupational exposure limit values (OELVs) are often set for reference periods of 8 h, but can also
be set for shorter periods or concentration excursions.
[SOURCE: ISO 18158:2016, 2.1.5.4, modified (Note 2 to entry is shortened)]
3.7
exposure (by inhalation)
situation in which a chemical agent is present in air that is inhaled by a person
---------------------- Page: 8 ----------------------
IEC FDIS 62990-2 IEC 2021 – 9 –
3.8
time weighted average concentration
TWA concentration
concentration of gas in air averaged over a reference period
3.9
fixed equipment
equipment fastened to a support, or otherwise secured in a specific location, when energized
3.10
transportable equipment
equipment not intended to be carried by a person during operation, nor intended for fixed
installation
3.11
portable equipment
equipment intended to be carried by a person during its operation
Note 1 to entry: Portable equipment is battery powered and includes, but is not limited to;
a) hand-held equipment, typically less than 1 kg, which requires use of only one hand to operate,
b) personal monitors, similar in size and mass to the hand-held equipment, that are continuously operating while
they are attached to the user, and,
c) larger equipment that can be operated by the user while it is carried either by hand, by a shoulder strap or
carrying harness and which might or might not have a hand directed probe.
3.12
aspirated equipment
equipment that samples the atmosphere by drawing it to the sensor
Note 1 to entry: A hand operated or electric pump is often used to draw gas to the sensor.
3.13
alarm-only equipment
equipment with an alarm but not having an indication of measured value
3.14
sensing element
part of the sensor which is sensitive to the gas or vapour to be measured
3.15
sensor
assembly in which the sensing element is housed and that can also contain associated circuit
components
3.16
remote sensor
sensor that is separated from the equipment body and is connected to a gas detection control
unit, gas detection transmitter
3.17
gas detection transmitter
fixed gas detection equipment that provides a conditioned electronic signal or output indication
to a generally accepted industry standard (such as 4 to 20 mA), intended to be utilized with
separate gas detection control units or signal processing data acquisition, central monitoring
and similar systems, which typically process information from various locations and sources
including, but not limited to gas detection equipment
---------------------- Page: 9 ----------------------
– 10 – IEC FDIS 62990-2 IEC 2021
3.18
separate gas detection control unit
equipment intended to provide display indication, alarm functions, output contacts or alarm
signal outputs or any combination when operated with gas detection transmitters(s)
3.19
alarm set point
setting of the equipment at which the measured concentration will cause the equipment to
initiate an indication, alarm or other output function
3.20
fault signal
audible, visible or other type of output, different from the alarm signal, permitting, directly or
indirectly, a warning or indication that the equipment is not working satisfactorily
3.21
sample line
means by which the gas being sampled is conveyed to the sensor
Note 1 to entry: Accessories such as filter or water trap are often included in the sample line.
3.22
sampling probe
separate accessory sample line which is optionally attached to the equipment
Note 1 to entry: It is usually short (for example in the order of 1 m) and rigid, although it can be telescopic. In some
cases it is connected by a flexible tube to the equipment.
3.23
field calibration kit
means of presenting test gas to the equipment for the purpose of calibrating, adjusting or
verifying the operation of the equipment
Note 1 to entry: The field calibration kit can be used for verifying the operation of the alarms if the concentration of
the test gas is above the alarm set-point.
Note 2 to entry: A mask for calibration and test is an example of a field calibration kit.
3.24
zero indication
indication given by an equipment when exposed to zero gas in normal operating conditions
3.25
indication range
range of measured values of gas concentration over which the equipment is capable of
indicating (see Figure 1)
3.26
lower limit of indication
smallest measured value within the indication range (see Figure 1)
3.27
upper limit of indication
largest measured value within the indication range (see Figure 1)
3.28
measuring range
range of measured values of gas concentration over which the accuracy of the equipment lies
within specified limits (see Figure 1)
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IEC FDIS 62990-2 IEC 2021 – 11 –
3.29
lower limit of measurement
smallest measured value within the measuring range (see Figure 1)
3.30
upper limit of measurement
largest measured value within the measuring range (see Figure 1)
Figure 1 – Relationship between indication range and measuring range (See 6.3.1)
3.31
expanded uncertainty
U
quantity defining an interval about a result of a measurement, expected to encompass a large
fraction of the distribution of values that could reasonably be attributed to the measurand
[SOURCE: ISO 18158:2016, 2.4.2.5]
3.32
zero uncertainty
quantity defining an interval about zero expected to encompass a large fraction of the
distribution of values that could reasonably be attributed to the measurement in clean air
Note 1 to entry: In Figure 2 the mean value of the measured values in clean air is not equal to zero to illustrate that
there can be an offset due to drift. The mean value can be above or below zero.
Figure 2 – Example of zero uncertainty
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3.33
selectivity
degree of independence from interfering gases
3.34
averaging time
period of time for which the measuring procedure yields an averaged value
3.35
drift
variation in the equipment indication over time at any fixed gas volume fraction (including clean
air) under constant ambient conditions
3.36
time of recovery
t(x)
time interval, with the equipment in a warmed-up condition, between the time when an
instantaneous change from standard test gas to clean air is produced at the equipment inlet
and the time when the indication reaches a stated percentage (x) of the initial indication
Note 1 to entry: For alarm only equipment the stated indication can be represented by the de-activation of the alarm
set at a stated value.
3.37
time of response
t(x)
time interval, with the equipment in a warmed-up condition, between the time when an
instantaneous change between clean air and the standard test gas, or vice versa, is produced
at the equipment inlet, and the time when the response reaches a stated percentage (x) of the
stabilized signal on the test gas
Note 1 to entry: The time of response is not applicable to spot-reading equipment.
3.38
warm-up time
time interval, with the equipment in a stated atmosphere, between the time when the equipment
is switched on and the time when the indication
...
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