Stationary source emissions - Determination of mass concentration of sulphur oxides - Standard reference method

This European Standard specifies the standard reference method (SRM) for the determination of the sulphuric oxide SO2 in flue gases emitted to the atmosphere from ducts and stacks. It is based on a sampling system and two analytical principles: ion chromatography and the Thorin method.
This European Standard specifies the performance characteristics to be determined and the performance criteria to be fulfilled by measuring systems based on the measurement method. It applies to periodic monitoring and to the calibration or control of automatic measuring systems (AMS) permanently installed on a stack, for regulatory or other purposes.
This European Standard specifies criteria for demonstration of equivalence of an alternative method to the SRM by application of prEN 14793.
This European Standard has been evaluated during field tests on waste incineration, co-incineration and large combustion installations. It has been validated for sampling periods of 30 min in the range of 0,5 mg/m³ to 2 000 mg/m³ of SO2 for an ion-chromatography variant and 5 mg/m³ to 2 000 mg/m³ of SO2 for the Thorin method according to emission limit values laid down in the Directive 2010/75/EC.
The limit values of EU Directives are expressed in units of mg/m³ of SO2 on dry basis and at standard conditions of 273 K and 101,3 kPa.
NOTE   The characteristics of installations, the conditions during field tests and the values of repeatability and reproducibility in the field are given in Annex E.

Emissionen aus stationären Quellen - Bestimmung der Massenkonzentration von Schwefeloxiden - Standardreferenzverfahren

Diese Europäische Norm legt das Standardreferenzverfahren (SRM) zur Bestimmung des SO2-Gehalts in Abgasen, die aus Abgaskanälen in die Atmosphäre emittiert werden, fest. Es basiert auf einer Probenahmeeinrichtung und zwei analytischen Verfahren: die Ionenchromatographie und das Thorin-Verfahren.
Diese Europäische Norm legt zu bestimmende Verfahrenskenngrößen und Mindestanforderungen fest, die von Messeinrichtungen auf Basis dieses Messverfahrens eingehalten werden müssen. Sie gilt für wiederkehrende Messungen und für die Kalibrierung oder Überprüfung von automatischen Messeinrichtungen (AMS), die aus gesetzgeberischen oder anderen Gründen stationär an einem Abgaskanal installiert sind.
Diese Europäische Norm legt Anforderungen zum Nachweis der Gleichwertigkeit von Alternativverfahren (AM) mit dem Standardreferenzverfahren (SRM) durch Anwendung der prEN 14793 fest.
Diese Europäische Norm wurde in Feldversuchen an Abfallverbrennungsanlagen, Mitverbrennungsanlagen und Großfeuerungsanlagen validiert. Sie wurde mit Probenahmedauern von 30 min im Bereich von 0,5 mg/m3 bis 2 000 mg/m3 SO2 mit der ionenchromatographischen Variante und von 5 mg/m3 bis 2 000 mg/m3 SO2 für das Thorin-Verfahren validiert, entsprechend den in der Richtlinie 2010/75/EU festgelegten Emissionsgrenzwerten.
   In den EU-Richtlinien werden die Grenzwerte ausgedrückt in Milligramm SO2 je Kubikmeter in trockenem Gas und bei Normbedingungen von 273 K und 101,3 kPa.
ANMERKUNG   Die Einzelheiten der Anlagen, die Bedingungen bei den Feldversuchen und die Werte der Wiederhol- und der Vergleichpräzision im Feld werden in Anhang E aufgeführt.

Emissions de sources fixes - Détermination de la concentration massique des oxydes de soufre - Méthode de référence normalisée

La présente Norme européenne spécifie la méthode de référence normalisée (SRM) pour la détermination du dioxyde de soufre SO2 dans les effluents gazeux émis dans l'atmosphère par les conduits et cheminées. Elle est basée sur un système de prélèvement et deux principes d'analyse : la chromatographie d'échange d'ions et la méthode au Thorin.
La présente Norme européenne spécifie les caractéristiques de performance devant être déterminées et les critères de performance devant être remplis par les systèmes de mesurage fondés sur cette méthode de mesurage. Elle s'applique à la surveillance périodique et à l'étalonnage ou au contrôle des systèmes de mesurage automatisés (AMS, Automatic Measuring Systems) installés à demeure sur une cheminée, à des fins réglementaires ou à d'autres fins.
La présente Norme européenne spécifie les critères permettant de démontrer l'équivalence d'une méthode « alternative » à la méthode de référence normalisée par l'application du prEN 14793.
La présente Norme européenne a été évaluée au cours d’essais sur site pratiqués sur les installations destinées à l’incinération des déchets, à la coincinération et sur des grandes installations de combustion. Elle a été validée pour des périodes de prélèvement de 30 min, dans la gamme de 0,5 mg/m3 à 2 000 mg/m3 de SO2 pour la chromatographie d'échange d'ions et de 5 mg/m3 à 2 000 mg/m3 of SO2 pour la méthode au Thorin, conformément aux valeurs limites d'émission spécifiées dans la Directive 2010/75/CE.
Les valeurs limites des directives UE sont exprimées en mg/m3 de SO2, sur gaz secs et dans les conditions normales de 273 K et 101,3 kPa.
NOTE   Les caractéristiques des installations, les conditions des essais sur site et les valeurs de répétabilité et de reproductibilité sur site sont indiquées à l'Annexe E.

Emisije nepremičnih virov - Določevanje masne koncentracije žveplovega dioksida - Standardna referenčna metoda

Ta evropski standard določa standardno referenčno metodo (SRM) za določanje žveplovega dioksida SO2 v dimnih plinih, ki prehajajo v ozračje iz vodov in odvodnikov. Temelji na sistemu vzorčenja in dveh analitičnih metodah: ionski kromatografiji in Thorinovi metodi.
Ta evropski standard določa lastnosti zmogljivosti in merila zmogljivosti, ki jih morajo izpolnjevati merilni sistemi na podlagi te merilne metode. Uporablja se za redno spremljanje in umerjanje ali nadzor avtomatskih merilnih sistemov (AMS), ki so trajno nameščeni na odvodnik, in sicer za zakonske ter druge namene.
Ta evropski standard določa merila za prikaz enakovrednosti alternativne metode standardni referenčni metodi z uporabo standarda prEN 14793.
Ta evropski standard je bil ocenjen med preskusi sežiganja odpadkov, sosežiga in velikih kurilnih naprav na terenu. Potrjen je bil za 30-minutna obdobja vzorčenja v razponu 0,5–2000 mg/m³ SO2 za različico z ionsko kromatografijo in 5–2000 mg/m³ SO2 za Thorinovo metodo v skladu z mejnimi vrednostmi emisij, opredeljenimi v Direktivi 2010/75/ES.
Mejne vrednosti direktiv EU so izražene v mg/m³ SO2 na suhi osnovi in pri standardnih pogojih 273 K in 101,3 kPa.
OPOMBA:   Lastnosti naprav, pogoji med preskusi na terenu ter vrednosti ponovljivosti in reprodukcije na terenu so podani v dodatku A.

General Information

Status
Published
Public Enquiry End Date
08-Feb-2015
Publication Date
11-Jun-2017
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
30-May-2017
Due Date
04-Aug-2017
Completion Date
12-Jun-2017

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Emissionen aus stationären Quellen - Bestimmung der Massenkonzentration von Schwefeloxiden - StandardreferenzverfahrenEmissions de sources fixes - Détermination de la concentration massique des oxydes de soufre - Méthode de référence normaliséeStationary source emissions - Determination of mass concentration of sulphur oxides - Standard reference method13.040.40Stationary source emissionsICS:Ta slovenski standard je istoveten z:EN 14791:2017SIST EN 14791:2017en,fr,de01-julij-2017SIST EN 14791:2017SLOVENSKI

STANDARDSIST EN 14791:20051DGRPHãþD
SIST EN 14791:2017
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 14791
January
t r s y ICS
s uä r v rä v r Supersedes EN
s v y { sã t r r wEnglish Version

Stationary source emissions æ Determination of mass concentration of sulphur oxides æ Standard reference method Emissions de sources fixes æ Détermination de la concentration massique des oxydes de soufre æ Méthode de référence normalisée

Emissionen aus stationären Quellen æ Bestimmung der Massenkonzentration von Schwefeloxiden æ Standardreferenzverfahren This European Standard was approved by CEN on

t x September
t r s xä

egulations which stipulate the conditions for giving this European Standard the status of a national standard without any alterationä Upætoædate lists and bibliographical references concerning such national standards may be obtained on application to the CENæCENELEC Management Centre or to any CEN memberä

translation under the responsibility of a CEN member into its own language and notified to the CENæCENELEC Management Centre has the same status as the official versionsä

CEN members are the national standards bodies of Austriaá Belgiumá Bulgariaá Croatiaá Cyprusá Czech Republicá Denmarká Estoniaá Finlandá Former Yugoslav Republic of Macedoniaá Franceá Germanyá Greeceá Hungaryá Icelandá Irelandá Italyá Latviaá Lithuaniaá Luxembourgá Maltaá Netherlandsá Norwayá Polandá Portugalá Romaniaá Serbiaá Slovakiaá Sloveniaá Spainá Swedená Switzerlandá Turkey and United Kingdomä

EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre:
Avenue Marnix 17,
B-1000 Brussels

t r s y CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Membersä Refä Noä EN

s v y { sã t r s y ESIST EN 14791:2017
EN 14791:2017 (E) 2 Contents Page

European foreword ....................................................................................................................................................... 5 1 Scope .................................................................................................................................................................... 6 2 Normative references .................................................................................................................................... 6 3 Terms and definitions ................................................................................................................................... 7 4 Symbols and abbreviations ...................................................................................................................... 13 4.1 Symbols ............................................................................................................................................................ 13 4.2 Abbreviated terms ....................................................................................................................................... 14 5 Principle .......................................................................................................................................................... 14 5.1 General ............................................................................................................................................................. 14 5.2 Measuring principle .................................................................................................................................... 14 6 Description of measuring system ........................................................................................................... 15 6.1 Reagents .......................................................................................................................................................... 15 6.1.1 General ............................................................................................................................................................. 15 6.1.2 Hydrogen peroxide ...................................................................................................................................... 15 6.1.3 Water ................................................................................................................................................................ 15 6.1.4 Absorption solution, H2O2 ......................................................................................................................... 15 6.1.5 Reagents for chromatographic analysis .............................................................................................. 15 6.1.6 Reagent for Thorin analysis ..................................................................................................................... 16 6.2 Sampling equipment ................................................................................................................................... 17 6.2.1 General ............................................................................................................................................................. 17 6.2.2 Sampling probe ............................................................................................................................................. 17 6.2.3 Filter housing ................................................................................................................................................. 17 6.2.4 Particle filter .................................................................................................................................................. 18 6.2.5 Temperature controller ............................................................................................................................. 18 6.2.6 Absorbers ........................................................................................................................................................ 18 6.2.7 Sample gas pump .......................................................................................................................................... 18 6.2.8 Gas volume meter ........................................................................................................................................ 18 6.3 Analysis equipment ..................................................................................................................................... 19 6.3.1 Ion chromatograph ...................................................................................................................................... 19 6.3.2 Thorin method .............................................................................................................................................. 19 7 Performance characteristics of the SRM .............................................................................................. 20 7.1 General ............................................................................................................................................................. 20 7.2 Performance characteristics of the sampling system ..................................................................... 21 7.3 Performance characteristics of the analysis ...................................................................................... 21 7.3.1 Sources of uncertainty ................................................................................................................................ 21 7.3.2 Performance criterion of analysis ......................................................................................................... 22 7.4 Establishment of the uncertainty budget ............................................................................................ 22 8 Field operation .............................................................................................................................................. 23 8.1 Measurement planning .............................................................................................................................. 23 8.2 Sampling strategy......................................................................................................................................... 23 8.2.1 General ............................................................................................................................................................. 23 8.2.2 Measurement section and measurement plane ................................................................................ 23 SIST EN 14791:2017

EN 14791:2017 (E) 3 8.2.3 Minimum number and location of measurement points ............................................................... 24 8.2.4 Measurement ports and working platform ......................................................................................... 24 8.3 Assembling the equipment........................................................................................................................ 24 8.4 Heating of the sample gas line ................................................................................................................. 24 8.5 Leak test ........................................................................................................................................................... 24 8.6 Performing sampling ................................................................................................................................... 25 8.6.1 Introduction of the sampling probe in the duct ................................................................................ 25 8.6.2 Sampling .......................................................................................................................................................... 25 8.6.3 Rinsing of the sampling system and preparation of the samples ............................................... 25 8.7 Measurement series .................................................................................................................................... 26 8.8 Field blank ....................................................................................................................................................... 26 8.9 Absorption efficiency .................................................................................................................................. 26 8.9.1 General ............................................................................................................................................................. 26 8.9.2 Test of absorption efficiency .................................................................................................................... 26 9 Analytical procedure ................................................................................................................................... 27 9.1 General ............................................................................................................................................................. 27 9.2 Ion Chromatography method ................................................................................................................... 27 9.2.1 General procedure ....................................................................................................................................... 27 9.2.2 Interferences .................................................................................................................................................. 28 9.2.3 Calibration....................................................................................................................................................... 28 9.3 Thorin Method ............................................................................................................................................... 29 9.3.1 Pre-treatment of sample solution before analysis for Thorin method ..................................... 29 9.3.2 General procedure ....................................................................................................................................... 29 9.3.3 Preparation of a chemical blank solution ............................................................................................ 30 9.3.4 Interferents ..................................................................................................................................................... 30 10 Expression of results ................................................................................................................................... 31 11 Equivalence of Thorin and ion chromatography methods ............................................................ 33 11.1 General ............................................................................................................................................................. 33 11.2 Range ................................................................................................................................................................. 33 11.3 Matrix effect .................................................................................................................................................... 33 11.4 Comparison of repeatability and trueness .......................................................................................... 33 12 Equivalence of an alternative method .................................................................................................. 34 13 Measurement report ................................................................................................................................... 34 Annex A (informative)

Validation of the method in the field..................................................................... 35 A.1 General ............................................................................................................................................................. 35 A.2 Round robin test of analytical methods ............................................................................................... 35 A.3 Field tests ......................................................................................................................................................... 36 A.3.1 General ............................................................................................................................................................. 36 A.3.2 Characteristics of installations ................................................................................................................ 36 A.3.3 Limits of quantification .............................................................................................................................. 38 A.3.4 Repeatability and reproducibility .......................................................................................................... 38 A.3.4.1 General ............................................................................................................................................................. 38 A.3.4.2 Repeatability .................................................................................................................................................. 39 A.3.4.3 Reproducibility .............................................................................................................................................. 41 A.3.5 Absorption efficiency .................................................................................................................................. 42 SIST EN 14791:2017

EN 14791:2017 (E) 4 Annex B (informative)

Examples of absorbers ............................................................................................... 43 Annex C (informative)

Example of assessment of compliance of standard reference method for SO2 with requirements on emission measurements ................................................................ 44 C.1 Introduction ................................................................................................................................................... 44 C.2 Elements required for the uncertainty determinations ................................................................ 44 C.3 Example of an uncertainty calculation ................................................................................................. 44 C.3.1 Specific conditions in the field................................................................................................................. 44 C.3.2 Performance characteristics .................................................................................................................... 46 C.3.3 Model equation and application of rule of uncertainty propagation ........................................ 47 C.3.3.1 Concentration of SO2 ................................................................................................................................... 47 C.3.3.2 Calculation of the combined uncertainty of m,refV and mC ........................................................... 48 C.3.3.3 Calculation of sensitivity coefficients ................................................................................................... 48 C.3.3.4 Results of the standard uncertainties calculations.......................................................................... 49 C.3.4 Estimation of the combined uncertainty ............................................................................................. 52 Annex D (informative)

Type of sampling equipment ................................................................................... 53 Annex E (informative)

Example of comparison of repeatability and trueness

of Thorin Method and Ion Chromatography Method .......................................................................................... 54 Annex F (informative)

Calculation of the uncertainty associated with a concentration expressed on dry gas and at an oxygen reference concentration .............................................. 64 F.1 Uncertainty associated with a concentration expressed on dry gas ......................................... 64 F.2 Uncertainty associated with a concentration expressed at a oxygen reference concentration ................................................................................................................................................ 66 Annex G (informative)

Significant technical changes .................................................................................. 68 Bibliography ................................................................................................................................................................. 69

SIST EN 14791:2017

EN 14791:2017 (E) 5 European foreword This document (EN 14791:2017) has been prepared by Technical Committee CEN/TC 264 “Air quality”, the secretariat of which is held by DIN. This document supersedes EN 14791:2005. 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 July 2017, and conflicting national standards shall be withdrawn at the latest by July 2017. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. Annex G provides details of significant technical changes between this document and the previous edition. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. SIST EN 14791:2017

EN 14791:2017 (E) 6 1 Scope This European Standard specifies the standard reference method (SRM) for the determination of the sulphuric oxide SO2 in flue gases emitted to the atmosphere from ducts and stacks. It is based on a sampling system and two analytical principles: ion chromatography and the Thorin method.

This European Standard specifies the performance characteristics to be determined and the performance criteria to be fulfilled by measuring systems based on the measurement method. It applies to periodic monitoring and to the calibration or control of automatic measuring systems (AMS) permanently installed on a stack, for regulatory or other purposes.

This European Standard specifies criteria for demonstration of equivalence of an alternative method to the SRM by application of EN 14793:2017. This European Standard has been validated during field tests on waste incineration, co-incineration and large combustion installations. It has been validated for sampling periods of 30 min in the range of 0,5 mg/m3 to 2 000 mg/m3 of SO2 for an ion-chromatography variant and 5 mg/m3 to 2 000 mg/m3 of SO2 for the Thorin method according to emission limit values laid down in the Directive 2010/75/EU. NOTE 1

Emission limit values for SO2 laid down in the Directive 2010/75/EU are in the range of 30 mg/m3 to 800 mg/m3. The emission limit values of EU Directives are expressed in units of mg/m3 of SO2 on dry basis and at standard conditions of 273 K and 101,3 kPa. NOTE 2 The characteristics of installations, the conditions during field tests and the values of repeatability and reproducibility in the field are given in Annex A. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. prEN 13284-1:2015, Stationary source

wã Manual gravimetric method EN 14793:2017, Stationary source emission – Demonstration of equivalence of an alternative method with a reference method EN 15259:2007, Air quality - Measurement of stationary source emissions - Requirements for measurement sections and sites and for the measurement objectiveá plan and report EN ISO 14956:2002, Air quality - Evaluation of the suitability of a measurement procedure by comparison with a required measurement uncertainty (ISO 14956:2002) ISO/IEC Guide 98-3:2008, Uncertainty of measurement — Part

yã Guide to the expression of uncertainty in measurement (GUM:1995) SIST EN 14791:2017

EN 14791:2017 (E) 7 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 standard reference method SRM reference method prescribed by European or national legislation

[SOURCE: EN 15259:2007] 3.2 reference method RM measurement method taken as a reference by convention, which gives the accepted reference value of the measurand Note 1 to entry: A reference method is fully described. Note 2 to entry: A reference method can be a manual or an automated method. Note 3 to entry: Alternative methods can be used if equivalence to the reference method has been demonstrated. [SOURCE: EN 15259:2007] 3.3

measurement method method described in a written procedure containing all the means and procedures required to sample and analyse, namely field of application, principle and/or reactions, definitions, equipment, procedures, presentation of results, other requirements and measurement report [SOURCE: EN 14793:2017] 3.4 alternative method

measurement method which complies with the criteria given by this European Standard with respect to the reference method

Note 1 to entry:

An alternative method can consist of a simplification of the reference method. [SOURCE: EN 14793:2017] 3.5 measuring system set of one or more measuring instruments and often other devices, including any reagent and supply, assembled and adapted to give information used to generate measured quantity values within specified intervals for quantities of specified kinds

[SOURCE: JCGM 200:2012] SIST EN 14791:2017

EN 14791:2017 (E) 8 3.6 automated measuring system AMS entirety of all measuring instruments and additional devices for obtaining a result of measurement Note 1 to entry: Apart from the actual measuring device (the analyser), an AMS includes facilities for taking samples (e.g. probe, sample gas lines, flow meters and regulator, delivery pump) and for sample conditioning (e.g. dust filter, pre-separator for interferents, cooler, converter). This definition also includes testing and adjusting devices that are required for functional checks and, if applicable, for commissioning. Note 2 to entry: The term “automated measuring system” (AMS) is typically used in Europe. The term “continuous emission monitoring system” (CEMS) is also typically used in the UK and USA. [SOURCE: EN 15267-4:2017] 3.7 calibration

set of operations that establish, under specified conditions, the relationship between values of quantities indicated by a measuring method or measuring system, and the corresponding values given by the applicable reference

Note 1 to entry: In case of automated measuring systems (AMS) permanently installed on a stack the applicable reference is the standard reference method (SRM) used to establish the calibration function of the AMS. Note 2 to entry: In case of manual methods the applicable reference can be reference materials used as calibration standards to establish the relationship between the output signal of the analytical device and the reference values.

Note 3 to entry: Calibration should not be confused with adjustment of a measuring system. 3.8 measurand particular quantity subject to measurement

[SOURCE: EN 15259:2007] Note 1 to entry:

The measurand is a quantifiable property of the stack gas under test, for example mass concentration of a measured component, temperature, velocity, mass flow, oxygen content and water vapour content. 3.9 influence quantity quantity that is not the measurand but that affects the result of the measurement Note 1 to entry: Influence quantities are e.g. ambient temperature, atmospheric pressure, presence of interfering gases in the flue gas matrix or pressure of the gas sample. 3.10 measurement series several successive measurements carried out on the same measurement plane and at the same process operating conditions SIST EN 14791:2017

EN 14791:2017 (E) 9 3.11 measurement site place on the waste gas duct in the area of the measurement plane(s) consisting of structures and technical equipment, for example working platforms, measurement ports, energy supply

Note 1 to entry: Measurement site is also known as sampling site. [SOURCE: EN 15259:2007] 3.12 measurement plane plane normal to the centreline of the duct at the sampling position Note 1 to entry: Measurement plane is also known as sampling plane. [SOURCE: EN 15259:2007] 3.13 measurement port opening in the waste gas duct along the measurement line, through which access to the waste gas is gained Note 1 to entry: Measurement port is also known as sampling port or access port. [SOURCE: EN 15259:2007] 3.14 measurement line line in the measurement plane along which the measurement points are located, bounded by the inner duct wall Note 1 to entry: Measurement line is also known as sampling line. [SOURCE: EN 15259:2007] 3.15 measurement point position in the measurement plane at which the sample stream is extracted or the measurement data are obtained directly

Note 1 to entry: Measurement point is also known as sampling point. [SOURCE: EN 15259:2007] 3.16 performance characteristic one of the quantities (described by values, tolerances, range) assigned to equipment in order to define its performance SIST EN 14791:2017

EN 14791:2017 (E) 10 3.17 quantification limit lowest amount of an analyte that is quantifiable with a given confidence level Note 1 to entry:

For a manual method the limit of quantification is usually calculated as 10 times the standard deviation of blank measurements provided that the blank value is negligible. This corresponds to a confidence level of 95 %.

3.18 absorption efficiency

ratio of quantity of the analyte q1 collected in the first absorber divided by the quantity of the analyte collected in the first and the second absorber (q1 + q2)

= q1 / (q1 + q2) 3.19 absorber device in which sulphur oxide is absorbed into an absorption liquid 3.20 repeatability in the laboratory closeness of the agreement between the results of successive measurements of the same measurand carried out under the same conditions of measurement Note 1 to entry: These conditions include: — same measurement method; — same laboratory; — same measuring system, used under the same conditions; — same location; — repetition over a short period of time. Note 2 to entry: Repeatability can be expressed quantitatively in terms of the dispersion characteristics of the results. Note 3 to entry: In this European Standard the repeatability is expressed as a value

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