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.

General Information

Status
Published
Publication Date
08-Jun-2021
Current Stage
6060 - International Standard published
Start Date
09-Jun-2021
Completion Date
09-Jun-2021
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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 ----------------------
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---------------------- 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

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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

---------------------- Page: 10 ----------------------
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

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– 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.

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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.
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– 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.
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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.

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– 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

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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
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– 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

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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– 12 – IEC FDIS 62990-2  IEC 2021
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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