prEN IEC 62990-1

Workplace Atmospheres - Part 1: Gas detectors - Performance requirements of detectors for toxic gases

This part of IEC 62990 specifies general requirements for design, function and performance, and describes the test methods that apply to portable, transportable, and fixed equipment for the detection and concentration measurement of toxic gases and vapours in workplace atmospheres and other industrial and commercial applications. This document is applicable to continuously sensing equipment whose primary purpose is to provide an indication, alarm and/or other output function the purpose of which is to indicate the presence of a toxic gas or vapour in the atmosphere and in some cases to initiate automatic or manual protective action(s). It is applicable to equipment in which the sensor generates an electrical signal when gas is present. This document applies to two types of equipment: - Type HM (Health Monitoring) ‘occupational exposure’ equipment: For occupational exposure measurement, the performance requirements are focused on uncertainty of measurement of gas concentrations in the region of Occupational Exposure Limit Values (OELV). The upper limit of measurement will be defined by the manufacturer in accordance with 4.2.1. - Type SM (Safety Monitoring) ‘general gas detection’ equipment: For general gas detection applications (e.g. safety warning, leak detection), the performance requirements are focused on alarm signalling. The upper limit of measurement will be defined by the manufacturer according to the intended use of the equipment. In general, the requirements for accuracy will be higher for Type HM equipment than for Type SM equipment. The same equipment may meet the requirements of both Type HM and Type SM. For equipment used for sensing the presence of multiple gases this document applies only to the detection of toxic gas or vapour. This document is not applicable to equipment: - with samplers and concentrators such as sorbents or paper tape having an irreversible indication; - used for the measurement of gases and vapours related to the risk of explosion; - used for the measurement of oxygen; – used only in laboratories for analysis or measurement; - used only for process measurement purposes; - used in the domestic environment; - used in environmental air pollution monitoring; - used for open-path (line of sight) area gas measurement; - used for ventilation control in car parks or tunnels.

Arbeitsplatzatmosphäre – Teil 1: Gasmessgeräte – Anforderungen an das Betriebsverhalten von Geräten für die Messung toxischer Gase

Atmosphères des lieux de travail - Partie 1: Détecteurs de gaz - Exigences d'aptitude à la fonction des détecteurs de gaz toxiques

IEC 62990-1:2019 spécifie les exigences générales pour la conception, la fonction et l’aptitude au fonctionnement, et décrit les méthodes d’essai qui s’appliquent aux matériels portables, transportables et fixes pour la détection et le mesurage de la concentration des gaz et des vapeurs toxiques dans les atmosphères des lieux de travail et d’autres applications industrielles et commerciales. Le présent document s’applique aux matériels à fonctionnement continu dont l’objectif principal est de donner une indication, une alarme et/ou une autre fonction de sortie, le but étant de signaler la présence d’un gaz ou d’une vapeur toxique dans l’atmosphère et, dans certains cas, de déclencher une ou des actions protectrices manuelles ou automatiques. Il s’applique aux matériels dont le capteur produit un signal électrique en présence d’un gaz. Le présent document s’applique à deux types de matériels: • Les matériels “d'exposition professionnelle” de type HM (surveillance de la santé): Pour le mesurage de l’exposition professionnelle, les exigences d’aptitude à la fonction ciblent l'incertitude de mesure des concentrations de gaz dans l’étendue d’application des valeurs limites d’exposition professionnelle (OELV – Occupational Exposure Limit Values). La limite supérieure de mesure est définie par le constructeur conformément à 4.2.1. • Les matériels de “détection générale de gaz” de type SM (surveillance de la sécurité): Pour les applications de détection générale de gaz (par exemple, avertissement de sécurité, détection de fuite), les exigences d’aptitude à la fonction ciblent la signalisation d’alarme. La limite supérieure de mesure est définie par le constructeur en fonction de l’utilisation prévue du matériel. Généralement, les exigences d’exactitude sont plus strictes pour les matériels de type HM que pour les matériels de type SM. Les mêmes matériels peuvent satisfaire aux exigences applicables aux deux types HM et SM. Pour les matériels qui permettent de détecter la présence de plusieurs gaz, le présent document s’applique uniquement pour la détection des gaz ou vapeurs toxiques. Le présent document ne s’applique pas aux matériels: - comportant des échantillonneurs et des concentrateurs tels que des sorbants ou une bande de papier qui présentent une indication irréversible; - utilisés pour le mesurage des gaz et vapeurs liés au risque d’explosion; - utilisés pour le mesurage de l’oxygène; - utilisés uniquement en laboratoires pour l’analyse ou le mesurage; - utilisés uniquement pour la mesure de processus; - utilisés dans l’environnement domestique; - utilisés dans la surveillance de la pollution atmosphérique; - utilisés pour le mesurage des gaz avec emplacement à chemin ouvert (champ de vision); - utilisés pour la commande de la ventilation dans les parcs de stationnement ou les tunnels. Le contenu du corrigendum de décembre 2019 a été pris en considération dans cet exemplaire.

Zrak na delovnem mestu - 1. del: Detektorji plina - Zahteve za delovanje detektorjev strupenih plinov

General Information

• Status: Not Published
• ICS: 29.260.20 - Electrical apparatus for explosive atmospheres
• Technical Committee: CLC/SC 31-9 - Electrical apparatus for the detection and measurement of combustible gases to be used in industrial
• Current Stage: 4020 - Enquiry circulated
• Due Date: 10-Dec-2021
• Completion Date: 10-Dec-2021
• Ref Project: oSIST prEN IEC 62990-1:2022 - Workplace Atmospheres - Part 1: Gas detectors - Performance requirements of detectors for toxic gases

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN IEC 62990-1:2022
01-februar-2022
Zrak na delovnem mestu - 1. del: Detektorji plina - Zahteve za delovanje
detektorjev strupenih plinov
Workplace Atmospheres - Part 1: Gas detectors - Performance requirements of
detectors for toxic gases

Atmosphères des lieux de travail - Partie 1: Détecteurs de gaz - Exigences d'aptitude à

la fonction des détecteurs de gaz toxiques
Ta slovenski standard je istoveten z: prEN IEC 62990-1
ICS:
13.040.30 Kakovost zraka na delovnem Workplace atmospheres
mestu
13.320 Alarmni in opozorilni sistemi Alarm and warning systems
oSIST prEN IEC 62990-1:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN IEC 62990-1:2022
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oSIST prEN IEC 62990-1:2022
EUROPEAN STANDARD DRAFT
prEN IEC 62990-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2021
ICS 29.260.20
English Version
Workplace Atmospheres - Part 1: Gas detectors - Performance
requirements of detectors for toxic gases
(IEC 62990-1:2019 + COR1:2019)
Atmosphères des lieux de travail - Partie 1: Détecteurs de To be completed

gaz - Exigences d'aptitude à la fonction des détecteurs de (IEC 62990-1:2019 + COR1:2019)

gaz toxiques
(IEC 62990-1:2019 + COR1:2019)
This draft European Standard is submitted to CENELEC members for enquiry.
Deadline for CENELEC: 2022-03-04.

The text of this draft consists of the text of IEC 62990-1:2019 (31/1463/FDIS) + COR1:2019.

If this draft becomes a European Standard, CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which

stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CENELEC in three official versions (English, French, German).

A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to

the CEN-CENELEC Management Centre has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the

Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.

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 supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and

shall not be referred to as a European Standard.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2021 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Project: 71712 Ref. No. prEN IEC 62990-1 E
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oSIST prEN IEC 62990-1:2022
prEN IEC 62990-1:2021 (E)
European foreword

This document (prEN IEC 62990-1:2021) consists of the text of IEC 62990-1:2019 and

IEC 62990-1:2019/COR1:2019 prepared by IEC/TC 31 “Equipment for explosive atmospheres” in cooperation

with ISO/TC 146 “Air quality, sub-committee 2: Workplace atmospheres”.
This document is currently submitted to the Enquiry.
The following dates are proposed:
• latest date by which the existence of this document (doa) dor + 6 months
has to be announced at national level
• latest date by which this document has to be (dop) dor + 12 months
implemented at national level by publication of an
identical national standard or by endorsement
• latest date by which the national standards (dow) dor + 36 months
conflicting with this document have to be withdrawn (to be confirmed or
modified when voting)
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oSIST prEN IEC 62990-1:2022
IEC 62990-1
Edition 1.0 2019-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Workplace atmospheres –
Part 1: Gas detectors – Performance requirements of detectors for toxic gases
Atmosphères des lieux de travail –
Partie 1: Détecteurs de gaz – Exigences d'aptitude à la fonction des détecteurs
de gaz toxiques
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-7080-6

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.

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oSIST prEN IEC 62990-1:2022
– 2 – IEC 62990-1:2019 © IEC 2019
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 8

3 Terms and definitions ...................................................................................................... 8

4 General requirements .................................................................................................... 16

4.1 Overview............................................................................................................... 16

4.2 Design .................................................................................................................. 17

4.2.1 General ......................................................................................................... 17

4.2.2 Indicating devices .......................................................................................... 17

4.2.3 Alarm signal .................................................................................................. 19

4.2.4 Fault signals .................................................................................................. 19

4.2.5 Adjustments ................................................................................................... 20

4.2.6 Battery-powered equipment ........................................................................... 20

4.2.7 Gas detection transmitter for use with separate gas detection control

units .............................................................................................................. 20

4.2.8 Separate gas detection control units for use with gas detection

transmitter(s) ................................................................................................. 21

4.2.9 Software-controlled equipment ...................................................................... 21

4.3 Labelling and marking ........................................................................................... 22

4.4 Instruction manual ................................................................................................ 23

5 Test methods ................................................................................................................. 25

5.1 General ................................................................................................................. 25

5.2 General requirements for tests .............................................................................. 26

5.2.1 Samples and sequence of tests ..................................................................... 26

5.2.2 Preparation of equipment before each test..................................................... 27

5.2.3 Mask for calibration and test .......................................................................... 28

5.3 Normal conditions for test ..................................................................................... 28

5.3.1 General ......................................................................................................... 28

5.3.2 Test gas(es) .................................................................................................. 28

5.3.3 Flow rate for test gases ................................................................................. 28

5.3.4 Power supply ................................................................................................. 29

5.3.5 Temperature .................................................................................................. 29

5.3.6 Pressure ........................................................................................................ 29

5.3.7 Humidity ........................................................................................................ 29

5.3.8 Acclimation time ............................................................................................ 29

5.3.9 Orientation ..................................................................................................... 29

5.3.10 Communications options ................................................................................ 29

5.3.11 Gas detection equipment as part of systems .................................................. 30

5.4 Tests .................................................................................................................... 30

5.4.1 General ......................................................................................................... 30

5.4.2 Unpowered storage ....................................................................................... 30

5.4.3 Measurement of deviations ............................................................................ 31

5.4.4 Mechanical tests ............................................................................................ 31

5.4.5 Environmental tests ....................................................................................... 33

5.4.6 Performance tests ......................................................................................... 36

5.4.7 Electrical tests ............................................................................................... 41

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IEC 62990-1:2019 © IEC 2019 – 3 –

5.4.8 Stability ......................................................................................................... 44

5.4.9 Fault signal tests ........................................................................................... 45

5.4.10 Software controlled equipment ....................................................................... 46

5.4.11 Protection against water ................................................................................ 46

6 Uncertainty of measurement and lower limit of measurement for type HM

equipment ..................................................................................................................... 47

6.1 General ................................................................................................................. 47

6.2 Method of calculation of uncertainty of measurement ............................................ 47

6.2.1 Basic concept ................................................................................................ 47

6.2.2 Sources of uncertainty ................................................................................... 48

6.2.3 Calculation of relative expanded uncertainty .................................................. 53

6.3 Method of calculation of lower limit of measurement ............................................. 54

6.4 Acceptance criteria ............................................................................................... 55

6.4.1 Uncertainty of measurement .......................................................................... 55

6.4.2 Lower limit of measurement ........................................................................... 55

6.5 Relation between uncertainty and accuracy .......................................................... 55

Annex A (normative) Gas specific performance requirements .............................................. 56

Annex B (informative) Determination of time of response and time of recovery .................... 57

B.1 Aspirated equipment ............................................................................................. 57

B.1.1 Test rig .......................................................................................................... 57

B.1.2 Equipment without internal pump ................................................................... 57

B.1.3 Equipment with internal pump ........................................................................ 57

B.2 Equipment that samples by diffusion ..................................................................... 58

B.2.1 Calibration mask method ............................................................................... 58

B.2.2 Diffusion or flow methods .............................................................................. 58

Bibliography .......................................................................................................................... 60

Figure 1 – Relationship between indication range and measuring range ............................... 14

Figure 2 – Warm-up time in clean air (typical) ....................................................................... 15

Figure 3 – Warm-up time in standard test gas (typical) ......................................................... 15

Figure 4 – Example of zero uncertainty ................................................................................. 16

Figure B.1 – Schematic example of test rig for use with aspirated equipment ........................ 58

Figure B.2 – Schematic example of test chamber for diffusion method .................................. 59

Figure B.3 – Schematic example of test chamber for flow method ......................................... 59

Table 1 – Factors to be considered in the expanded uncertainty estimate ............................. 48

Table A.1 – Gas specific performance requirements ............................................................. 56

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oSIST prEN IEC 62990-1:2022
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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WORKPLACE ATMOSPHERES –
Part 1: Gas detectors –
Performance requirements of detectors for toxic gases
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 62990-1 has been prepared by Joint Working Group (JWG) 45 of

IEC technical committee 31: Equipment for explosive atmospheres in cooperation with

ISO technical committee 146: Air quality, sub-committee 2: Workplace atmospheres.

It is published as a dual logo standard.
The text of this International Standard is based on the following documents:
FDIS Report on voting
31/1463/FDIS 31/1480/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.
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oSIST prEN IEC 62990-1:2022
IEC 62990-1:2019 © IEC 2019 – 5 –

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 62990 series, 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.

The contents of the corrigendum of December 2019 have been included in this copy.

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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oSIST prEN IEC 62990-1:2022
– 6 – IEC 62990-1:2019 © IEC 2019
INTRODUCTION

This part of IEC 62990 specifies general requirements for construction, testing and

performance of equipment intended to measure the concentration of toxic gas and vapour in

workplace atmospheres and other industrial and commercial applications. The performance

requirements are intended to apply under environmental conditions present at the site of

operation. However, because a wide range of environmental conditions are encountered in

practise, this document specifies requirements that have to be fulfilled by equipment when

tested under prescribed laboratory conditions.

This document applies to the following types of equipment: Health Monitoring (HM) and Safety

Monitoring (SM). For a given measurement task of Type HM equipment the range over which

the requirements must be met depends on the occupational exposure limit value. However, for

most toxic gases and vapours the occupational exposure limit values have not been

harmonized at the international level. Therefore, it was decided to use a reference value

instead of the occupational exposure limit value for the performance tests. The list of

reference values is given in Annex A. The reference values chosen are equal to or close to

the occupational exposure limit values used in different countries but are intended to be used

only for type testing equipment without any legal implications.

Electrical equipment used for the direct detection and direct concentration measurement of

toxic gases and vapours generate readings in clean air (nominally zero), which vary with

environmental conditions and time. This document therefore includes test methods and

requirements for acceptable variations in measured values at application of zero gas and of

defined test gases.

For gas detection equipment including additional function for detecting flammable gas and/or

oxygen, consideration should be given to the relevant standards.

General requirements for construction, testing and performance of gas detectors for

flammable gases and vapours are set out in IEC 60079-29-1, Explosive atmospheres –

Part 29-1: Gas detectors – Performance requirements of detectors for flammable gases.

General requirements for construction, testing and performance of open path detectors for

flammable gases are set out in IEC 60079-29-4, Explosive atmospheres – Part 29-4: Gas

detectors – Performance requirements of open path detectors for flammable gases.

Guidance for the selection, installation, use and maintenance of gas detecting equipment is

set out in IEC 60079-29-2: Explosive atmospheres – Part 29-2, Gas detectors – Selection,

installation, use and maintenance of detectors for flammable gases and oxygen.

Guidance for functional safety of fixed gas detection systems is set out in IEC 60079-29-3:

Explosive atmospheres – Part 29-3, Gas detectors – Guidance on functional safety of fixed

gas detection systems.
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oSIST prEN IEC 62990-1:2022
IEC 62990-1:2019 © IEC 2019 – 7 –
WORKPLACE ATMOSPHERES –
Part 1: Gas detectors –
Performance requirements of detectors for toxic gases
1 Scope

This part of IEC 62990 specifies general requirements for design, function and performance,

and describes the test methods that apply to portable, transportable, and fixed equipment for

the detection and concentration measurement of toxic gases and vapours in workplace

atmospheres and other industrial and commercial applications.

This document is applicable to continuously sensing equipment whose primary purpose is to

provide an indication, alarm and/or other output function the purpose of which is to indicate

the presence of a toxic gas or vapour in the atmosphere and in some cases to initiate

automatic or manual protective action(s). It is applicable to equipment in which the sensor

generates an electrical signal when gas is present.
This document applies to two types of equipment:
• Type HM (Health Monitoring) ‘occupational exposure’ equipment:

For occupational exposure measurement, the performance requirements are focused on

uncertainty of measurement of gas concentrations in the region of Occupational Exposure

Limit Values (OELV). The upper limit of measurement will be defined by the manufacturer

in accordance with 4.2.1.
• Type SM (Safety Monitoring) ‘general gas detection’ equipment:

For general gas detection applications (e.g. safety warning, leak detection), the

performance requirements are focused on alarm signalling. The upper limit of

measurement will be defined by the manufacturer according to the intended use of the

equipment.

In general, the requirements for accuracy will be higher for Type HM equipment than for Type

SM equipment. The same equipment may meet the requirements of both Type HM and Type

SM.

For equipment used for sensing the presence of multiple gases this document applies only to

the detection of toxic gas or vapour.
This document is not applicable to equipment:

– with samplers and concentrators such as sorbents or paper tape having an irreversible

indication;

– used for the measurement of gases and vapours related to the risk of explosion;

– used for the measurement of oxygen;
– used only in laboratories for analysis or measurement;
– used only for process measurement purposes;
– used in the domestic environment;
– used in environmental air pollution monitoring;
– used for open-path (line of sight) area gas measurement;
– used for ventilation control in car parks or tunnels.
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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 60068-2-6, Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)

IEC 60079-0, Explosive atmospheres – Part 0: Equipment – General requirements
IEC 60529, Degrees of protection provided by enclosures (IP Code)

IEC 61000-4-29, Electromagnetic compatibility (EMC) – Part 4-29: Testing and measurement

techniques – Voltage dips, short interruptions and voltage variations on d.c. input power port

immunity tests

IEC 61000-6-3, Electromagnetic compatibility (EMC) – Part 6-3: Generic standards –

Emission standard for residential, commercial and light-industrial environments

IEC 61000-6-4, Electromagnetic compatibility (EMC) – Part 6-4: Generic standards –

Emission standard for industrial environments

IEC 61326-1, Electrical equipment for measurement, control and laboratory use – EMC

requirements – Part 1: General requirements
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

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
3.1
gas properties
3.1.1
ambient air
normal atmosphere surrounding the equipment
3.1.2
clean air

air that is free of gases or vapours which the sensor is sensitive to or which influence the

performance of the sensor
3.1.3
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).
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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)]
3.1.4
reference value

value used as the basis to specify requirements such as measuring

range, resolution and alarm set point

Note 1 to entry: The term reference value is used in this document because for most toxic gases and vapours the

occupational exposure limit values have not been harmonized at the International level.

3.1.5
poisons
substances that lead to temporary or permanent change of
performance, particularly loss of sensitivity of the sensing element
3.1.6
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”.

3.1.7
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,
...