EN 14181:2004

SLOVENSKI STANDARD
01-december-2004
(PLVLMHQHSUHPLþQLKYLURY=DJRWDYOMDQMHNDNRYRVWLDYWRPDWVNLKPHULOQLK
VLVWHPRY
Stationary source emissions - Quality assurance of automated measuring systems
Emissionen aus stationären Quellen - Qualitätssicherung für automatische
Messeinrichtungen
Émissions des sources fixes - Assurance qualité des systemes automatiques de mesure
Ta slovenski standard je istoveten z: EN 14181:2004
ICS:
13.040.40 (PLVLMHQHSUHPLþQLKYLURY Stationary source emissions
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 14181
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2004
ICS 13.040.40
English version
Stationary source emissions - Quality assurance of automated
measuring systems
Émission des sources fixes - Assurance qualité des Emissionen aus stationären Quellen - Qualitätssicherung
systèms automatiques de mesure für automatische Messeinrichtungen
This European Standard was approved by CEN on 3 November 2003.
CEN 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. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2004 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 14181:2004: E
worldwide for CEN national Members.

Contents
Page
Foreword.3
Introduction .4
1 Scope .5
2 Normative references .5
3 Terms and definitions .5
4 Symbols and abbreviations .9
5 Principle.11
6 Calibration and validation of the AMS (QAL2).13
7 Ongoing quality assurance during operation (QAL3).21
8 Annual Surveillance Test (AST) .23
9 Documentation.27
Annex A (normative) QAL2 and AST functional test of AMS.28
Annex B (normative) Test of linearity .32
Annex C (normative) CUSUM Control Charts .34
Annex D (informative) Documentation.40
Annex E (informative) Example of calculation of the calibration function and of the variability test .42
Annex F (informative) Example of calculation of the standard deviation s of the AMS at zero
AMS
and span level .51
Annex G (informative) Example of using the calibration function and  the variability test in the
AST.54
Annex H (informative) CUSUM charts field form (drift) .58
Bibliography .59

Foreword
This document (EN 14181:2004) has been prepared by Technical Committee CEN/TC 264 “Air quality”, the
secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by December 2004, and conflicting national standards shall be withdrawn
at the latest by December 2004.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association. It supports requirements in the EU Directives 2000/76/EC [1] and
2001/80/EC [2] and may also be applicable for other purposes.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland
and United Kingdom.
Introduction
This standard describes the quality assurance procedures needed to assure that an Automated Measuring
System (AMS) installed to measure emissions to air are capable of meeting the uncertainty requirements on
measured values given by legislation, e.g. EU Directives [1], [2] or national legislation, and 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 of the AMS and its measuring procedure are described in EN ISO 14956 (QAL1)
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.
1 Scope
This European Standard 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 standard 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 standard is designed to be used after the AMS has been accepted according to the procedures specified
in EN ISO 14956 (QAL1).
This standard is restricted to quality assurance (QA) of the AMS, and does not include the QA of the data
collection and recording system of the plant.
2 Normative references
This European Standard incorporates by dated or undated reference, provisions from other publications.
These normative references are cited at the appropriate places in the text, and the publications are listed
hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to
this European Standard only when incorporated in it by amendment or revision. For undated references the
latest edition of the publication referred to applies (including amendments).
EN ISO 14956, Air quality - Evaluation of the suitability of a measurement procedure by comparison with a
required measurement uncertainty (ISO 14956:2002).
EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories (ISO/IEC
17025:1999).
3 Terms and definitions
For the purposes of this European Standard, the following terms and definitions apply.
3.1
air quality characteristic
one of the quantifiable properties relating to an air mass under investigation, for example, concentration of a
constituent
[ISO 6879:1995]
3.2
automated measuring system AMS
measuring system permanently installed on site for continuous monitoring of emissions
NOTE 1 An AMS is a method which is traceable to a reference method.
NOTE 2 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, moisture removal devices, converters,
diluters). This definition also includes testing and adjusting devices, that are required for regular functional checks.
3.3
calibration function
linear relationship between the values of the SRM and the AMS with the assumption of a constant residual
standard deviation
3.4
competent authority
organisation or organisations which implement the requirements of EU Directives and regulate installations
which must comply with the requirements of this European Standard
3.5
confidence interval (two-sided)
when T and T are two functions of the observed values such that, θ being a population parameter to be
1 2
estimated, the probability P (T ≤ θ ≤ T ) is at least equal to (1 – α) [where (1 – α) is a fixed number, positive
r 1 2
and less than 1], the interval between T and T is a two-sided (1 – α) confidence interval for θ
1 2
[ISO 3534-1:1993]
NOTE The 95 % confidence interval 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.
Figure 1 — Illustration of the 95 % confidence interval of a normal distribution
In this European Standard, the standard deviation σ is estimated in QAL2 by parallel measurements with a SRM. It is
assumed that the requirement for σ , presented in terms of an allowable uncertainty budget i.e. variability, is provided by
the regulators (e.g. in some EU Directives). In the procedures of this standard, the premise is that the required variability is
given as σ itself, or as a quarter of the length of the full 95 % confidence interval.
3.6
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
3.7
drift
monotonic change of the calibration function over stated period of unattended operation, which results in a
change of the measured value
3.8
emission limit value
limit value related to the uncertainty requirement
NOTE For the EU directives [1] and [2] it is the daily emission limit value that relates to the uncertainty requirement.
3.9
extractive AMS
AMS having the detection unit physically separated from the gas stream by means of a sampling system
3.10
instability
change in the measured value comprised of drift and dispersion resulting from the change in the calibration
function over a stated period of unattended operation, for a given value of the air quality characteristic. Drift
and dispersion specify the monotonic and stochastic change with time of the output signal, respectively
[ISO 6879:1995]
3.11
instrument reading
indication of the measured value directly provided by the AMS without using the calibration function
3.12
legislation
directives, Acts, ordinances and regulations
3.13
measurand
particular quantity subject to measurement
[ENV 13005:1999]
3.14
measured value
estimated value of the air quality characteristic derived from an output signal; this usually involves calculations
related to the calibration process and conversion to required quantities
[ISO 6879:1995]
3.15
non-extractive AMS
AMS having the detection unit in the gas stream or in a part of it
3.16
period of unattended operation
maximum admissible interval of time for which the performance characteristics will remain within a predefined
range without external servicing, e.g. refill, calibration, adjustment
[ISO 6879:1995]
3.17
peripheral AMS or SRM
measuring system or SRM used to gather the data required to convert the measured values to standard
reference conditions, i.e. AMS or SRM for moisture, temperature, pressure and oxygen
3.18
precision
closeness of agreement of results obtained from the AMS for successive zero readings and successive span
readings at defined time intervals
3.19
reference material
material simulating a known concentration of the input parameter, by use of surrogates and traceable to
national standards
NOTE Surrogates normally used are calibration gases, gas cells, gratings or filters.
3.20
response time
time taken for an AMS to respond to an abrupt change in value of the air quality characteristic
[ISO 6879:1995]
3.21
span reading
instrument reading of the AMS for a simulation of the input parameter at a fixed elevated concentration.
NOTE 1 This simulation should test as much as possible all the measuring elements of the system, which contribute
significantly to its performance.
NOTE 2 The span reading is approximately 80 % of the measured range.
3.22
standard conditions
conditions as given in the EU-directives to which measured values have to be standardised to verify
compliance with the emission limit values
3.23
standard deviation
positive square root of: the mean squared deviation from the arithmetic mean divided by the number of
degrees of freedom
NOTE The number of degrees of freedom is the number of measurements minus 1.
3.24
Standard Reference Method SRM
method described and standardised to define an air quality characteristic, temporarily installed on site for
verification purposes
NOTE Also known as a reference method.
3.25
uncertainty
parameter associated with the result of a measurement that characterises the dispersion of the values that
could reasonably be attributed to the measurand
[ENV 13005:1999]
3.26
variability
standard deviation of the differences of parallel measurements between the SRM and AMS
3.27
zero reading
instrument reading of the AMS on simulation of the input parameter at zero concentration
NOTE This simulation should test as much as possible all the measuring elements of the AMS, that contribute
significantly to its performance
4 Symbols and abbreviations
4.1 Symbols
a intercept of the calibration function
aˆ best estimate of a
b slope of the calibration function
ˆ
b best estimate of b
D difference between measured SRM value y and calibrated AMS value yˆ
i i i
D average of D
i
D amount by which the AMS has to be adjusted, in the case that drift is detected
adjust
d difference between actual instrument reading of the AMS and the reference value

t
d difference between previous instrument reading of the AMS and the reference value

t−1
E emission limit value
h test value for detection of a decrease in precision
s
h test value for detection of drift
x
k constant in the calculation in the provisional sum for standard deviation
s
k test value for variability (based on a χ -test, with a β-value of 50 %, for N numbers of
v
paired measurements)
k constant in the calculation in the provisional sum for positive and negative differences and
x
in the calculation of the required adjustment of the AMS
N number of paired samples in parallel measurements
N(s) number of readings since the standard deviation was different from zero
N(pos) number of readings since a positive difference was detected
N(neg) number of readings since a negative difference was detected
P percentage value
s provisional normalised sum of the standard deviations of the AMS (QAL3)
p
s provisional normalised sum of the standard deviations of the AMS at time t (QAL3)
t
s provisional normalised sum of the standard deviations of the AMS at time t-1 (QAL3)
t–1
s standard deviation of the differences D in parallel measurements
D i
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
others
standard deviation)
th
x i measured signal obtained with the AMS at AMS measuring conditions
i
x average of AMS measured signals x
i
x reference value at time t (QAL3)
t
th
y i result obtained with the SRM
i
y average of the SRM results y
i
SRM value y at standard conditions
y i
i,s
y lowest SRM value at standard conditions
s,min
y highest SRM value at standard conditions
s,max
yˆ best estimate for the ”true value”, calculated from the AMS measured signal x by means
i i
of the calibration function
yˆ best estimate for the ”true value”, calculated from the AMS measured signal x at

i,s i
standard conditions
y actual instrument reading of the AMS at time t (QAL3)
t
Z offset (the difference between the AMS zero reading and the zero)
Σ (pos) provisional normalised sum of the positive drift of the AMS
p
Σ (pos) normalised sum of the positive drift of the AMS at time t
t
Σ (pos) previous normalised sum of the positive drift of the AMS (at time t–1)
t–1
Σ (neg) provisional normalised sum of the negative drift of the AMS
p
Σ (neg) normalised sum of the negative drift of the AMS at time t
t
Σ (neg) previous normalised sum of the negative drift of the AMS (at time t–1)
t–1
s standard deviation of the AMS used in QAL3

AMS
α significance level
ε deviation between y and the expected value
i i
σ uncertainty derived from requirements of legislation
4.2 Abbreviations
AMS Automated Measuring System
AST Annual Surveillance Test
ELV Emission Limit Value
QA Quality Assurance
QAL Quality Assurance Level
QAL1 First Quality Assurance Level
QAL2 Second Quality Assurance Level
QAL3 Third Quality Assurance Level
QC Quality Control
SRM Standard Reference Method
5 Principle
5.1 General
An AMS to be used at installations covered by EU Directives, e.g. [1] and [2], shall have been proven suitable
for its measuring task (parameter and composition of the flue gas) by use of the QAL1 procedure, as specified
by EN ISO 14956. Using this standard, it shall be proven that the total uncertainty of the results obtained from
the AMS meets the specification for uncertainty stated in the applicable regulations. In QAL1 the total
uncertainty required by the applicable regulation is calculated by summing in an appropriate manner all the
relevant uncertainty components arising from the individual performance characteristics.
The QAL2 and AST procedures involve testing laboratories, whereas the QAL3 procedures involve the plant
operators.
QAL2 is a procedure for the determination of the calibration function and its variability, and a test of the
variability of the measured values of the AMS compared with the uncertainty given by legislation. The QAL2
tests are performed on suitable AMS that have been correctly installed and commissioned. A calibration
function is established from the results of a number of parallel measurements performed with a Standard
Reference Method (SRM). The variability of the measured values obtained with the AMS is then evaluated
against the required uncertainty.
The QAL2 procedures are repeated periodically, after a major change of plant operation, after a failure of the
AMS or as required by legislation.
QAL3 is a procedure which is used to check drift and precision in order to demonstrate that the AMS is in
control during its operation so that it continues to function within the required specifications for uncertainty.
This is achieved by conducting periodic zero and span checks on the AMS – based on those used in the
procedure for zero and span repeatability tests carried out in QAL1 – and then evaluating the results obtained
using control charts. Zero and span adjustments or maintenance of the AMS, may be necessary depending on
the results of this evaluation.
The AST is a procedure which is used to evaluate whether the measured values obtained from the AMS still
meet the required uncertainty criteria – as demonstrated in the previous QAL2 test. It also determines whether
the calibration function obtained during the previous QAL2 test is still valid. The validity of the measured
values obtained with the AMS is checked by means of a series of functional tests as well as by the
performance of a limited number of parallel measurements using an appropriate SRM.
5.2 Limitations
Figure 2 illustrates the components of the AMS covered by this standard.
Figure 2 — Limits for the QA of the AMS excluding the data recording system
NOTE 1 The influence of the uncertainty of the measurement results, which arise from the data acquisition recording
and handling system of the AMS or of the plant system, and its determination, are not covered from this standard.
NOTE 2 The performance of the data collection and recording system can be as influential as the AMS performance in
determining the quality of the results obtained from the whole measuring system/process. There are different requirements
for data collection recording and presentation in different countries.
When conducting parallel measurements, the measured signals from the AMS shall be taken directly from the
AMS (e.g. expressed as analogue or digital signal) during the QAL2 and AST procedures specified in this
standard, by using an independent data collection system provided by the organisation(s) carrying out the
QAL2 and AST tests. All data shall be recorded in their uncorrected form (without corrections e.g. for
temperature and oxygen). A plant data collection system with ongoing quality control can additionally be used
to collect the measured signal from the AMS.
5.3 Measurement site and installation
The AMS shall be installed in accordance with the requirements of the relevant European and/or international
standards. Special attention shall be given to ensure that the AMS is readily accessible for regular
maintenance and other necessary activities.
NOTE The AMS should be positioned as far as practical in a position where it measures a sample that is
representative of the stack gas composition.
All measurements shall be carried out on a suitable AMS and peripheral AMS installed within an appropriate
working environment.
The working platform used to access the AMS shall readily allow parallel measurements to be performed
using an SRM. The sampling ports for measurements with the SRM shall be placed as close as possible, but
not more than three times the equivalent diameter up- or down-stream of the location of the AMS, in order to
achieve comparable measurements between AMS and SRM.
It is necessary to have good access to the AMS to enable inspections to take place and also to minimise the
time taken to implement the quality assurance procedures of this standard. A clean, well-ventilated and well-lit
working space around the AMS is required to enable the staff to perform this work effectively. Suitable
protection is required for the personnel and the equipment, if the working platform is exposed to the weather.
5.4 Testing laboratories performing SRM measurements
The testing laboratories performing the measurements with the SRM shall have an accredited quality
assurance system according to EN ISO/IEC 17025, or shall be approved directly by the relevant competent
authority. They shall also have sufficient experience in performing the measurements using the appropriate
SRM. The SRM used shall be a European Standard, if available. If such a standard does not exist,
international or national standards shall apply so as to ensure the provision of data of an equivalent scientific
quality.
6 Calibration and validation of the AMS (QAL2)
6.1 General
Testing shall cover the following items:
— installation of the AMS;
— calibration of the AMS by means of parallel measurements with a SRM;
— determination of the variability of the AMS, and the check of compliance with the required uncertainty.
The sequence of the combined tests is shown in Figure 3.

Figure 3 — Flow diagram for the calibration and variability tests
A QAL2 procedure shall be performed for all measurands:
— at least every 5 years for every AMS or more frequently if so required by legislation or by the competent
authority (e.g. the EU Directive 2000/76/EC on the Incineration of Waste [1] specifies parallel
measurements every 3 years);
Furthermore, a QAL2 shall be performed for all the measurands influenced by:
— any major change in plant operation (e.g. change in flue gas abatement system or change of fuel), or
— any major changes or repairs to the AMS, which will influence the results obtained significantly.
The results of QAL2 shall be reported within 6 months after the changes. During the period before a new
calibration function has been established the previous calibration function (where necessary with
extrapolation) shall be used.
Examples of calculation of the calibration function and of the variability test are given in annex E.
6.2 Functional test
The requirements for installation and the measurement site as specified in 5.3 shall be fulfilled.
Before calibration (see 6.4 and 6.5) and the test for variability (see 6.6 and 6.7) are performed, it shall be
proven that the AMS is commissioned satisfactorily, e.g. as specified by the AMS supplier and/or
manufacturer. It shall also be shown and documented that the AMS gives a zero reading on a zero
concentration.
NOTE 1 For some AMS it is difficult to achieve a zero reading. In those situations, the AMS can be removed from the
stack, and zeroed using a test bench or similar. As an alternative, a measuring path, which enables this zero test to be
carried out, can be installed in the stack.
The functional test before calibration shall be performed according to annex A.
NOTE 2 The specific precautions to be taken should depend on the individual location. Special attention should be
made for particulate measurements.
6.3 Parallel measurements with an SRM
Parallel measurements shall be performed with the AMS and SRM in order to calibrate and validate the AMS
by use of an independent method.
It is not sufficient to use reference materials alone to obtain the calibration functions and this is therefore not
permitted. This is because these reference materials do not replicate sufficiently the matrix stack gas, they
cannot be used to establish that the sampling point(s) of the AMS are representative, and they are not used
with the sampling system in all cases. However, if there are limited variations in the results obtained in the
AMS/SRM tests, and the measured concentrations are well below the ELV, an extrapolation of the calibration
function to the ELV may be verified by the use of appropriate reference materials, taking into account the
effects of interfering substances on the AMS, where appropriate.
If clear and distinct operating modes of the plant process are part of its normal operation (for example
changes of fuel), additional calibrations shall be performed and a calibration function established for each
operational mode.
NOTE 1 It is recommended that a preliminary test be carried out in order to evaluate if a full calibration over the whole
concentration range can be performed. Otherwise a competent authority should judge, if, based on its experience, it is
reasonable to establish one calibration function that covers all normal changes in the process.
In order to ensure that the calibration function is valid for the range of conditions within which the plant will
operate, the concentrations during the calibration shall be varied as much as possible within the normal
operations of the plant. This shall ensure that the calibration of the AMS is valid over as large a range as
possible, and also that it covers most operational situations.
The test for variability shall be performed (see 6.7) for each calibration function, i.e. for each operating mode
of the plant.
An SRM shall be used to sample the emissions at a sampling plane in the duct, which is as close as possible
to the AMS, without the results obtained by each being influenced by the other.
The presence of the equipment specified in the SRM shall not influence or disturb the AMS measurements.
For each calibration a minimum of 15 valid parallel measurements shall be made with the plant operating
normally. These measurements shall be uniformly spread both over at least 3 days and over each of the
measuring days of normally 8 h to 10 h (e.g. not 5 measurements in the morning and none in the afternoon)
and be performed within a period of four weeks.
NOTE 2 The required spread of a minimum of 15 valid measurements over three days is essential in minimising the
effect of influences of the subsequent measurement results (i.e. to avoid auto-correlation between the calculated
differences in the results of the AMS and SRM). The alternative of performing more measurements within a shorter time
interval can lead to the establishment of an invalid calibration function.
NOTE 3 A minimum of 15 valid measurements can in practice require that more than 15 samples be taken, since some
samples may be deemed to be invalid during subsequent analysis because of inadequate quality.
NOTE 4 The requirement that the measurements need to be uniformly spread over at least 3 days does not imply that
the measurements need to be performed within 3 consecutive days.
A set of measurements is valid when all of the requirements below are fulfilled:
— the SRM measurements are performed according to the accepted standard;
— the time period of each AMS measured signal, is larger than 90 % of the averaging time (excluding all of
the measured signals which are above 100 % or below 0 % of the measuring range of the AMS, signals
obtained during internal checks (auto calibration), and signals obtained during any other malfunctioning of
the AMS).
During the parallel measurements with the AMS and SRM, each result is considered as a measurement pair
(one AMS measured signal and one SRM measured value) and these shall cover the same time period.
The sampling time for each of the parallel measurements shall be at least 30 min, or at least 4 times the
response time of the AMS, including the sampling system (as determined during the response time
measurements carried out during QAL1), whichever is the greater. In general the sampling time should equal
the shortest averaging time, which is required by the ELV specification. The recording system shall have an
averaging time significantly shorter than the response time of the AMS.
If the sampling time is shorter than 1 h, then the time interval between the start of each sample shall be longer
than 1 h.
The results obtained from the SRM shall be expressed under the same conditions as those measured by the
AMS (e.g. conditions of pressure, temperature, etc.). In order to establish the calibration function and perform
the variability test all additional parameters and values included in the corrections to AMS conditions and
standard conditions shall be obtained for each measurement pair.
EXAMPLE If the AMS measures gaseous HCl in units of mg/m in stack gas containing water vapour, then the SRM
results are expressed in the same units (e.g. mg/m in the stack gas with the same water vapour concentration).
6.4 Data evaluation
6.4.1 Preparation of data
The steps for providing data required for establishing the calibration function and performing the test of
variability are illustrated in Figure 4.

Figure 4 — Flow chart describing the steps in calibration procedure and test for variability .
The AMS shall be calibrated at the condition of the exhaust gas as measured by the AMS. Therefore, the
SRM values shall be converted to AMS measuring conditions, if necessary, giving SRM measured values y to
i
be expressed in concentration units (e. g mg/m ).
The measured signals from the AMS x can be either a signal in an electrical unit (e.g. mA or Volt) or in a
i
concentration unit (e.g. mg/m ).
NOTE For a non-extractive AMS, that measures the gas directly, the calibration function reported should be at the
operating conditions. For an extractive AMS measuring at specified conditions, the calibration function is reported at these
specified conditions.
6.4.2 Establishing the calibration function
It is presupposed in the standard that the calibration function is linear and has a constant residual standard
deviation. The calibration function shall be described by the model below (see ISO 11095):

The figure in the circles indicates the sequence of the steps.
y = a + b x + ε (1)
i i i
where
th
x is the i result of the AMS; i = 1 to N; N ≥ 15;
i
th
y is the i result of the SRM; i = 1 to N; N ≥15;
i
ε is the deviation between y and the expected value;
i i
a is the intercept of the calibration function;
b is the slope of the calibration function.
The general procedure requires a sufficient range of the measured concentrations to give a valid calibration of
the AMS for the complete range of concentrations encountered during normal operations. As stated in 6.3 it is
essential that the concentration range is as large as possible within the normal operation of the plant to allow
for a valid calibration function to be obtained. However, at a large number of plants, it may be difficult under
normal operating conditions to achieve a sufficiently large concentration range. In such cases, in which the
concentration range (measured with the SRM) is less than 15 % of the emission limit value, another (similar)
procedure is given below (procedure b).
NOTE 1 If the concentration range is slightly bigger than 15 %, and if procedure a) results in an inadequate calibration
function (e.g. a function with negative slope), procedure b) can be used instead.
The following quantities shall be calculated:
N
x = x (2)
i
∑
N
i=1
N
y = y (3)
i
∑
N
i=1
The difference ( y − y ) between the highest and lowest measured SRM concentration at standard
s,max s,min
conditions shall be calculated.
a) If ( y − y ) is greater than or equal to 15 % of the ELV, calculate:
s,max s,min
N
()x − x()y − y
i i
∑
i=1
ˆ
b = (4)
N
()x − x
i
∑
i=1
ˆ
aˆ = y −b x (5)
b) If ( y − y ) is smaller than 15 % of the ELV, calculate:
s,max s,min
y
ˆ
b = (6)
x − Z
ˆ
aˆ = −b Z (7)
where the offset Z is the difference between the AMS zero reading and zero.
NOTE 2 For several AMS the offset is 4 mA.
For procedure b) it is essential that, prior to the parallel measurements, it is proven that the AMS gives a
reading at or below detection limit (as demonstrated in QAL1) at a zero concentration (as stated in 6.2).
The results shall be plotted on an x-y graph in order to show explicitly the calibration function and the valid
calibration range.
6.5 Calibration function of the AMS and its validity
The calibration function is given by equation (8):
ˆ
yˆ = aˆ + b x (8)
i i
where
ˆ
y is the calibrated value of the AMS;
i
x is the AMS measured signal.
i
ˆ
Each measured signal x of the AMS shall be converted to a calibrated value y by means of the above
i i
calibration function.
NOTE 1 It is recommended that this calibration function is incorporated into the data processing system of the plant.
ˆ
NOTE 2 y is the calibrated measurement result obtained from the AMS. According to certain EU Directives (see [1],
i
[2]) the required uncertainty should be subtracted from that result before comparisons are made with the emission limit
value. That procedure is outside the scope of this standard. The calibrated result yˆ of the AMS is without subtraction of
i
the required uncertainty.
The calibration function is valid when the plant is operated within the valid calibration range. This valid
calibration range is defined as the calibration range from zero to yˆ , determined during the QAL2
s,max
procedure, plus an extension of 10 % of the calibration range beyond the highest value. This implies that only
values in the valid calibration range are valid measured values.
For measurements outside the valid calibration range, however, the calibration curve shall be extrapolated in
order to determine the concentration values, which exceed the valid calibration range.
If greater confidence in the performance of the AMS at ELV is required when the plant is emitting outside its
calibration range determined above, reference materials at zero and at a concentration close to ELV shall be
used, where available, as part of the calibration procedure to confirm the suitability of the linear extrapolation.
In this case, calculate the deviation between the calibrated measured value of the AMS at zero and ELV and
the corresponding SRM values. The deviation at ELV should be less than the uncertainty specified by
legislation. The deviation at zero should be less than 10 % of the ELV. If these criteria are not fulfilled then
further investigations shall be performed to establish the reasons for this.
The validity of the valid calibration range shall be evaluated by the plant owner on a weekly basis (Monday to
Sunday). A full new calibration (QAL2) shall be performed, reported and implemented within 6 months, if any
of the following conditions occur:
— more than 5 % of the number of AMS measured values calculated over this weekly period (based on
normalized calibrated values) are outside the valid calibration range for more than 5 weeks in the period
between two ASTs;
— more than 40 % of the number of AMS measured values calculated over this weekly period (based on
normalized calibrated values) are outside the valid calibration range for one or more weeks.
ˆ
If the best estimate of the true value y is outside the valid calibration range but below 50 % of ELV, then the
i,s
competent authority can allow the plant to perform an AST instead of the QAL2 procedures. If the AST
demonstrates that the existing calibration function is valid beyond the calibration range, the competent
authority can allow the plant to extend the calibration range up to the maximum measured concentrations (but
below 50 % of ELV) determined during the AST.
The existing calibration function shall be used until the new calibration function has been implemented.
Data from previous calibrations shall not be combined with data from a new calibration exercise when
calculating the calibration function.
Only calibrated values should be used when reporting to the authorities.
6.6 Calculation of variability
Identify the stated or required maximum uncertainty for the measured values from the AMS. Verify the exact
definition of this uncertainty (e.g. is it expressed as a 95 % confidence interval, a standard deviation, or any
other statistical formulation). If necessary, convert the required maximum uncertainty in terms of an absolute
standard deviation σ .
In the case where the uncertainty is expressed at a level of confidence of 95 %, the value of an absolute
standard deviation shall be determined by using a factor of 1,96 as the value for the coverage factor.
EXAMPLE In some EU Directives (see [1], [2]) the uncertainty of the AMS 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 = P E / 1,96 .
The variability test shall be performed on the measured values (calibrated values) of the AMS. Hence, for
ˆ
every parallel measurement the AMS measured value y shall be calculated using the calibration function
i
(see 6.5).
Where the requirements on the data quality are specified under standard conditions (as e.g. in the relevant EU
Directives [1] and [2]), the variability test shall be performed using concentrations under these conditions.
When calculating the variability, the peripheral parameters (e.g. moisture content, temperature and oxygen
concentration) used to standardise the measurements shall be taken from:
a) the SRM instrumentation for normalising the SRM results;
b) the plant instrumentation for normalising the AMS results, or in case these do not exist, the default values
used by the plant.
NOTE The purpose of this procedure is to ensure that the standardisation procedure carried out in the plant’s data
recording and processing system is includ
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