ISO/DIS 20181

Stationary source emissions — Quality assurance of automated measuring systems

This document specifies procedures for establishing quality assurance levels (QAL) for automated measuring systems (AMS) installed on industrial plants for the determination of the flue gas components and other flue gas parameters. This document specifies: — a procedure (QAL2) to calibrate the AMS and determine the variability of the measured values obtained by it, so as to demonstrate the suitability of the AMS for its application, following its installation; — a procedure (QAL3) to maintain and demonstrate the required quality of the measurement results during the normal operation of an AMS, by checking that the zero and span characteristics are consistent with those determined during QAL1; — a procedure for the annual surveillance tests (AST) of the AMS in order to evaluate (i) that it functions correctly and its performance remains valid and (ii) that its calibration function and variability remain as previously determined. This document is designed to be used after the AMS has been certified in accordance with the series of documents EN 15267.

Émission des sources fixes — Assurance qualité des systèmes automatiques de mesurage

General Information

• Status: Published
• Publication Date: 09-Feb-2023
• ICS: 13.040.40 - Stationary source emissions
• Technical Committee: ISO/TC 146/SC 1 - Stationary source emissions
• Drafting Committee: ISO/TC 146/SC 1 - Stationary source emissions
• Current Stage: 6060 - International Standard published
• Start Date: 10-Feb-2023
• Due Date: 01-Oct-2022
• Completion Date: 10-Feb-2023

Relations

• Parent: ISO 11698-2:2000 - Micrographics — Methods of measuring image quality produced by aperture card scanners — Part 2: Quality criteria and control
• Effective Date: 06-Jun-2022

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 20181
First edition
2023-02
Stationary source emissions — Quality
assurance of automated measuring
systems
Émission des sources fixes — Assurance qualité des systèmes
automatiques de mesurage
Reference number
ISO 20181:2023(E)
© ISO 2023
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ISO 20181:2023(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2023

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ISO 20181:2023(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction .............................................................................................................................................................................................................................. vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Symbols and abbreviated terms..........................................................................................................................................................6

4.1 Symbols ......................................................................................................................................................................................................... 6

4.2 Abbreviated terms .............................................................................................................................................................................. 7

5 Principle ........................................................................................................................................................................................................................ 7

5.1 General ........................................................................................................................................................................................................... 7

5.2 Limitations ................................................................................................................................................................................................. 9

5.3 Measurement site and installation ....................................................................................................................................... 9

5.4 Testing laboratories performing SRM measurements ..................................................................................... 10

6 Calibration and validation of the AMS (QAL2) ..................................................................................................................10

6.1 General ........................................................................................................................................................................................................ 10

6.2 Functional test ..................................................................................................................................................................................... 11

6.3 Parallel measurements with the SRM ............................................................................................................................12

6.4 Data evaluation ................................................................................................................................................................................... 14

6.4.1 Preparation of data ....................................................................................................................................................... 14

6.4.2 Selection of data points from automated SRM ..................................................................................... 15

6.4.3 Establishing the calibration function ........................................................................................................... 15

6.5 Calibration function of the AMS and its validity ................................................................................................... 16

6.6 Calculation of variability ............................................................................................................................................................ 18

6.7 Test of variability .............................................................................................................................................................................. 19

6.8 QAL2 report ...................................................................... ...................................................................................................................... 19

7 Ongoing quality assurance during operation (QAL3) ...............................................................................................20

7.1 General ........................................................................................................................................................................................................ 20

7.2 Procedures to maintain ongoing quality ..................................................................................................................... 21

7.3 Choosing control charts .............................................................................................................................................................. 21

7.4 Control chart limits ......................................................................................................................................................................... 22

7.4.1 General .....................................................................................................................................................................................22

7.4.2 Calculation of control chart limits using performance data ....................................................22

7.4.3 Calculation of control chart limits using the maximum permissible

uncertainty ...........................................................................................................................................................................23

7.5 Zero and span measurements ................................................................................................................................................23

7.5.1 General .....................................................................................................................................................................................23

7.5.2 Frequency of zero and span measurements ...........................................................................................23

7.5.3 Extractive gas analysis systems ........................................................................................................................ 24

7.5.4 In-situ gas-monitoring AMS .................................................................................................................................. 24

7.5.5 Particulate-monitoring AMS ................................................................................................................................. 25

7.6 Documentation of control charts ........................................................................................................................................ 25

8 Annual surveillance test (AST)..........................................................................................................................................................25

8.1 General ........................................................................................................................................................................................................ 25

8.2 Functional test ..................................................................................................................................................................................... 26

8.3 Parallel measurements with the SRM ............................................................................................................................ 26

8.4 Data evaluation ................................................................................................................................................................................... 27

8.5 Calculation of variability ............................................................................................................................................................28

8.6 Test of variability and validity of the calibration function ..........................................................................28

8.7 AST report ...............................................................................................................................................................................................29

9 Documentation ...................................................................................................................................................................................................29

iii
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ISO 20181:2023(E)

Annex A (normative) QAL2 and AST functional test of AMS ....................................................................................................30

Annex B (normative) Test of linearity .............................................................................................................................................................34

Annex C (informative) Control charts .............................................................................................................................................................36

Annex D (normative) Documentation .............................................................................................................................................................46

Annex E (informative) Examples of calculation of the calibration function and of the

variability test .....................................................................................................................................................................................................48

Annex F (informative) Example of calculation of the standard deviation s of the AMS at

AMS

zero and span level .........................................................................................................................................................................................63

Annex G (informative) Example of using the calibration function and testing the variability

and validity of the calibration function in the AST ......................................................................................................66

Annex H (informative) Implementation of QAL1 .................................................................................................................................70

Annex I (normative) k and t values .................................................................................................................................................71

v 0,95; N–1

Annex J (informative) Significant technical changes ......................................................................................................................72

Bibliography .............................................................................................................................................................................................................................74

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ISO 20181:2023(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.

This document was prepared by the European Committee for Standardization (CEN) (as EN 14181:2014)

and was adopted, without modification by Technical Committee ISO/TC 146, Air quality, Subcommittee

SC 1, Stationary source emission.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
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ISO 20181:2023(E)
Introduction

This document describes the quality assurance procedures needed to ensure that an automated

measuring system (AMS) installed to measure emissions to air are capable of meeting the uncertainty

[1],[2],[3]

requirements on measured values e.g. given by legislation or more generally by competent

authorities.

Three different quality assurance levels (QAL1, QAL2, and QAL3) are defined to achieve this objective.

These quality assurance levels cover the suitability of an AMS for its measuring task (e.g. before or

during the purchase period of the AMS), the validation of the AMS following its installation, and the

control of the AMS during its ongoing operation on an industrial plant. An annual surveillance test

(AST) is also defined.

The suitability evaluation (QAL1) of the AMS and its measuring procedure are described in EN 15267-

3 and ISO 14956 where a methodology is given for calculating the total uncertainty of AMS measured

values. This total uncertainty is calculated from the evaluation of all the uncertainty components

arising from its individual performance characteristics that contribute.
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INTERNATIONAL STANDARD ISO 20181:2023(E)
Stationary source emissions — Quality assurance of
automated measuring systems
1 Scope

This document specifies procedures for establishing quality assurance levels (QAL) for automated

measuring systems (AMS) installed on industrial plants for the determination of the flue gas

components and other flue gas parameters.
This document specifies:

— a procedure (QAL2) to calibrate the AMS and determine the variability of the measured values

obtained by it, so as to demonstrate the suitability of the AMS for its application, following its

installation;

— a procedure (QAL3) to maintain and demonstrate the required quality of the measurement results

during the normal operation of an AMS, by checking that the zero and span characteristics are

consistent with those determined during QAL1;

— a procedure for the annual surveillance tests (AST) of the AMS in order to evaluate (i) that it functions

correctly and its performance remains valid and (ii) that its calibration function and variability

remain as previously determined.

This document is designed to be used after the AMS has been certified in accordance with the series of

documents EN 15267.
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.

EN 15259:2007, Air quality — Measurement of stationary source emissions — Requirements for

measurement sections and sites and for the measurement objective, plan and report

EN 15267-1, Air quality — Certification of automated measuring systems — Part 1: General principles

EN 15267-2, Air quality — Certification of automated measuring systems — Part 2: Initial assessment of the

AMS manufacturer’s quality management system and post certification surveillance for the manufacturing

process

EN 15267-3, Air quality — Certification of automated measuring systems — Part 3: Performance criteria

and test procedures for automated measuring systems for monitoring emissions from stationary sources

ISO 14956, Air quality — Evaluation of the suitability of a measurement procedure by comparison with a

required measurement uncertainty
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
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ISO 20181:2023(E)
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
automated measuring system
AMS

measuring system permanently installed on site for continuous monitoring of emissions or

measurement of peripheral parameters
Note 1 to entry: An AMS is a method which is traceable to a reference method.

Note 2 to entry: Apart from the analyser, an AMS includes facilities for taking samples (e.g. sample probe, sample

gas lines, flow meters, regulators, delivery pumps) and for sample conditioning (e.g. dust filter, water vapour

removal devices, converters, diluters). This definition also includes testing and adjusting devices that are

required for regular functional checks.
3.2
extractive AMS

AMS having the detection unit physically separated from the gas stream by means of a sampling system

3.3
in-situ AMS
AMS having the detection unit in the gas stream or in a part of it
3.4
peripheral AMS

AMS used to gather the data required to convert the AMS measured value to standard conditions

Note 1 to entry: A peripheral AMS is used to measure e.g. water vapour, temperature, pressure and oxygen.

3.5
reference method

measurement method taken as a reference by convention, which gives the accepted reference value of

the measurand
[SOURCE: EN 15259:2007]
3.6
standard reference method
SRM
reference method prescribed by European or national legislation

Note 1 to entry: Standard reference methods are used e.g. to calibrate and validate AMS and for periodic

measurements to check compliance with limit values.
[SOURCE: EN 15259:2007]
3.7
peripheral SRM

SRM used to gather the data required to convert the SRM measured values to AMS or standard

conditions

Note 1 to entry: A peripheral SRM is used to measure e.g. water vapour, temperature, pressure and oxygen.

3.8
standard conditions

conditions to which measured values have to be standardized to verify compliance with emission limit

values
[1] [2] [3]
Note 1 to entry: Standard conditions are specified e.g. in EU Directives , and .
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ISO 20181:2023(E)
3.9
emission limit value
ELV
limit value related to the maximum permissible uncertainty
[1] [2] [3]

Note 1 to entry: For the EU Directives , and it is the daily emission limit value that relates to the uncertainty

requirement.
3.10
maximum permissible uncertainty

uncertainty requirement on AMS measured values given by legislation or competent authorities

3.11
legislation
directives, acts, ordinances or regulations
3.12
competent authority

organization or organizations which implement the requirements of EU Directives and regulate

installations which shall comply with the requirements of this document
3.13
calibration function

linear relationship between the values of the SRM and the AMS with the assumption of a constant

residual standard deviation

Note 1 to entry: For dust measuring AMS, a quadratic calibration function can be used as described in EN 13284-

3.14
standard deviation

positive square root of the mean squared deviation from the arithmetic mean divided by the number of

degrees of freedom

Note 1 to entry: The number of degrees of freedom is the number of measurements minus 1.

3.15
confidence interval

interval estimator (T , T ) for the parameter θ with the statistics T and T as interval limits and for

1 2 1 2
which it holds that P[T < θ < T ] ≥ (1 – α)
1 2
[SOURCE: ISO 3534-1:2006]

Note 1 to entry: The two-sided 95 % confidence interval of a normal distribution is illustrated in Figure 1, where:

T = Θ – 1,96 σ is the lower 95 % confidence limit;
1 0
T = Θ + 1,96 σ is the upper 95 % confidence limit;
2 0
I = T – T = 2 × 1,96 × σ is the length of the 95 % confidence interval;
2 1 0

σ = I / (2 × 1,96) is the standard deviation associated with a 95 % confidence interval;

n is the number of observed values;
f is the frequency;
m is the measured value.
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ISO 20181:2023(E)
Figure 1 — Illustration of the 95 % confidence interval of a normal distribution

In this document, the standard deviation σ is estimated in QAL2 by parallel measurements with

the SRM. It is assumed that the requirement for σ , presented in terms of a maximum permissible

uncertainty, is provided by the regulators (e.g. in some EU Directives). In the procedures of this

standard, the premise is that the maximum permissible uncertainty is given as σ itself, or as a quarter

of the length of the full 95 % confidence interval

Note 2 to entry: In some EU Directives (see [1],[2],[3]) the uncertainty of the AMS measured values is expressed

as half of the length of a 95 % confidence interval as a percentage P of the emission limit value E. Then, in order to

convert this uncertainty to a standard deviation, the appropriate conversion factor is σ =PE /, 196 .

3.16
variability

standard deviation of the differences of parallel measurements between the SRM and AMS

3.17
uncertainty

parameter associated with the result of a measurement that characterizes the dispersion of the values

that could reasonably be attributed to the measurand
[SOURCE: ISO/IEC Guide 98-3:2008]
3.18
measurand
particular quantity subject to measurement
[SOURCE: ISO/IEC Guide 98-3:2008]

Note 1 to entry: A measurand can be e.g. the mass concentration of a measured component or the waste gas

velocity, pressure or temperature.
3.19
measured component

constituent of the waste gas for which a defined measurand is to be determined by measurement

[SOURCE: EN 15259:2007]
3.20
peripheral parameter

specified physical or chemical quantity which is needed for conversion of measured values to specified

conditions
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ISO 20181:2023(E)
3.21
measured value
estimated value of the measurand derived from a measured signal

Note 1 to entry: This usually involves calculations related to the calibration process and conversion to required

quantities.

Note 2 to entry: A measured value is a short-term average. The averaging time can be e.g. 10 min, 30 min or 1 h.

3.22
instrument reading

measured signal directly provided by the AMS without using the calibration function

3.23
zero reading
instrument reading on simulation of the input parameter at zero concentration
3.24
span reading

instrument reading for a simulation of the input parameter at a fixed elevated concentration

3.25
instability

change in the measured signal comprised of drift and dispersion over a stated maintenance interval

Note 1 to entry: Drift and dispersion specify the monotonic and stochastic change with time of the measured

signal, respectively.
3.26
drift

monotonic change of the calibration function over stated maintenance interval, which results in a

change of the measured signal
3.27
precision

closeness of agreement of results obtained from the AMS for successive zero readings and successive

span readings at defined time intervals
3.28
response time

time interval between the instant of a sudden change in the value of the input quantity to an AMS and

the time as from which the value of the output quantity is reliably maintained above 90 % of the correct

value of the input quantity
Note 1 to entry: The response time is also referred to as the 90 % time.
3.29
maintenance interval

maximum admissible interval of time for which the performance characteristics will remain within a

predefined range without external servicing, e.g. refill, calibration, adjustment

3.30
reference material

substance or mixture of substances, with a known concentration within specified limits, or a device of

known characteristics
3.31
CUSUM chart

calculation procedure in which the amount of drift and change in precision is compared to the

corresponding uncertainty components which are obtained during QAL1
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ISO 20181:2023(E)
3.32
EWMA chart

calculation procedure in which the combined amount of drift and change in precision is compared to

the corresponding uncertainty components which are obtained during QAL1

Note 1 to entry: The EWMA chart averages the data in a way that gives less and less weight to data as they are

further removed in time.
4 Symbols and abbreviated terms
4.1 Symbols
intercept of the calibration function
best estimate of a
slope of the calibration function
best estimate of b
difference between SRM measured value y and calibrated AMS measured value ˆy
average of D
E emission limit value

test value for variability (based on a χ -test, with a β-value of 50 %, for N numbers of paired

measurements)
N number of paired samples in parallel measurements
P percentage value
standard deviation of the AMS used in QAL3
AMS
s standard deviation of the differences D in parallel measurements
D i

t value of the t distribution for a significance level of 95 % and a number of degrees of freedom

0,95; N–1
of N – 1
u uncertainty due to instability (expressed as a standard deviation)
inst

u uncertainty due to influence of temperature (expressed as a standard deviation)

temp
u uncertainty due to influence of pressure (expressed as a standard deviation)
pres
u uncertainty due to influence of voltage (expressed as a standard deviation)
volt

u any other uncertainty that may influence the zero and span reading (expressed as a standard

others
deviation)
x i measured signal obtained with the AMS at AMS measuring conditions
average of AMS measured signals x
i measured value obtained with the SRM
average of the SRM measured values y
SRM measured value y at standard conditions
i ,s
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ISO 20181:2023(E)
lowest SRM measured value at standard conditions
s,min
highest SRM measured value at standard conditions
s,max

best estimate for the ”true value”, calculated from the AMS measured signal x by means of

the calibration function

best estimate for the ”true value”, calculated from the AMS measured signal x at standard

i,s
conditions

ˆy best estimate for the ”true value”, calculated from the maximum value of the AMS measured

s,max
signals x at standard conditions
Z offset (the difference between the AMS zero reading and the zero)
α significance level
ε deviation between y and the expected value
i i

standard deviation associated with the uncertainty derived from requirements of legislat

...