EN 14212:2012

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.SORYHJDAußenluft - Messverfahren zur Bestimmung der Konzentration von Schwefeldioxid mit Ultraviolett-FluoreszenzQualité de l'air ambiant - Méthode normalisée pour le mesurage de la concentration en dioxyde de soufre par fluorescence U.V.Ambient air - Standard method for the measurement of the concentration of sulphur dioxide by ultraviolet fluorescence13.040.20Kakovost okoljskega zrakaAmbient atmospheresICS:Ta slovenski standard je istoveten z:EN 14212:2012SIST EN 14212:2012en,fr,de01-december-2012SIST EN 14212:2012SLOVENSKI
STANDARDSIST EN 14212:20051DGRPHãþD

EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 14212
August 2012 ICS 13.040.20 Supersedes EN 14212:2005English Version
Ambient air - Standard method for the measurement of the concentration of sulphur dioxide by ultraviolet fluorescence
Qualité de l'air ambiant - Méthode normalisée pour le mesurage de la concentration en dioxyde de soufre par fluorescence U.V.
Luftqualität - Messverfahren zur Bestimmung der Konzentration von Schwefeldioxid mit Ultraviolett-Fluoreszenz This European Standard was approved by CEN on 10 May 2012.
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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management Centre has the same status as the official versions.
CEN members are the national standards bodies of 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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
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Avenue Marnix 17,
B-1000 Brussels © 2012 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 14212:2012: ESIST EN 14212:2012

Test of lack of fit . 49Annex B (informative)
Sampling equipment. 51Annex C (informative)
Ultraviolet fluorescence analyser . 53Annex D (informative)
Manifold testing . 54Annex E (normative)
Type approval . 56Annex F (informative)
Calculation of uncertainty in field operation at the hourly limit value . 75Annex G (informative)
Calculation of uncertainty in field operation at the daily limit value . 83Annex H (informative)
Calculation of uncertainty in field operation at the annual critical level . 93Annex I (informative)
Significant technical changes . 103Bibliography . 104 SIST EN 14212:2012

NOTE 2 When the standard is used for other purposes than for measurements required by Directive 2008/50/EC, the ranges and uncertainty requirements may not apply. The method covers the determination of ambient air concentrations of sulphur dioxide in zones classified as rural areas, urban-background areas and traffic-orientated locations and locations influenced by industrial sources.
The results are expressed in µg/m3 (at 20 °C and 101,3 kPa). NOTE 3 1 000 µg/m3 of SO2 corresponds to 376 nmol/mol of SO2. This standard contains information for different groups of users. Clauses 5 to 7 and Annexes C and D contain general information about the principles of sulphur dioxide measurement by ultraviolet fluorescence analyser and sampling equipment. Clause 8 and Annex E are specifically directed towards test houses and laboratories that perform type-approval testing of sulphur dioxide analysers. These sections contain information about:  Type-approval test conditions, test procedures and test requirements;  Analyser performance requirements;  Evaluation of the type-approval test results;  Evaluation of the uncertainty of the measurement results of the sulphur dioxide analyser based on the type-approval test results. Clauses 9 to 11 and Annexes F and G are directed towards monitoring networks performing the practical measurements of sulphur dioxide in ambient air. These sections contain information about:  Initial installation of the analyser in the monitoring network and acceptance testing;  Ongoing quality assurance/quality control;  Calculation and reporting of measurement results;  Evaluation of the uncertainty of measurement results under practical monitoring conditions. 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. SIST EN 14212:2012

(ISO 6144) EN ISO 6145-6, Gas analysis — Preparation of calibration gas mixtures using dynamic volumetric methods — Part 6: Critical orifices (ISO 6145-6) EN ISO 6145-7, Gas analysis — Preparation of calibration gas mixtures using dynamic volumetric methods — Part 7: Thermal mass-flow controllers (ISO 6145-7) EN ISO 6145-10, Gas analysis — Preparation of calibration gas mixtures using dynamic volumetric methods — Part 10: Permeation method (ISO 6145-10) EN ISO 14956, Air quality — Evaluation of the suitability of a measurement procedure by comparison with a required measurement uncertainty (ISO 14956) EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
(ISO/IEC 17025) ENV 13005:1999, Guide to the expression of uncertainty in measurement 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 adjustment set of operations carried out on a measuring system so that it provides prescribed indications corresponding to given values of a quantity to be measured
Note 1 to entry: Types of adjustment of a measuring system include zero adjustment of a measuring system, offset adjustment, and span adjustment (sometimes called gain adjustment). Note 2 to entry: Adjustment of a measuring system should not be confused with calibration, which is a prerequisite for adjustment. [SOURCE: JCGM 200:2012 (VIM) [2]] Note 3 to entry: In the context of this standard, adjustment is performed on measurement data rather than on the analyser. 3.2 ambient air outdoor air in the troposphere, excluding workplaces as defined by Directive 89/654/EEC, where provisions concerning health and safety at work apply and to which members of the public do not have regular access [SOURCE: 2008/50/EC [1]] SIST EN 14212:2012

3.3 analyser measuring system that provides an output signal which is a function of the concentration, partial pressure, flow or temperature of one or more components of a gas mixture 3.4 availability of the analyser fraction of the time period for which valid measuring data of the ambient air concentration is available from an analyser
3.5 calibration operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties and, in a second step, uses this information to establish a relation for obtaining a measurement result from an indication Note 1 to entry:
A calibration may be expressed by a statement, calibration function, calibration diagram, calibration curve, or calibration table. In some cases, it may consist of an additive or multiplicative correction of the indication with associated measurement uncertainty. Note 2 to entry: Calibration should not be confused with adjustment of a measuring system, often mistakenly called “self-calibration”, nor with verification of a calibration. Note 3 to entry: Often, the first step alone in the above definition is perceived as being calibration. [SOURCE: JCGM 200:2012 (VIM) [2]] Note 4 to entry
In the context of this standard, calibration is a comparison of the analyser response to a known gas concentration with a known uncertainty when the information obtained from the comparison is used for the successive adjustment (if needed) of the analyser. 3.6 certification range concentration range for which the analyser is type-approved 3.7 check verification that the analyser is still operating within specified performance limits 3.8 combined standard uncertainty standard uncertainty of the result of a measurement when that result is obtained from the values of a number of other quantities, equal to the positive square root of a sum of terms, the terms being the variances or co-variances of these other quantities weighted according to how the measurement result varies with changes in these quantities [SOURCE: ENV 13005:1999] 3.9 coverage factor numerical factor used as a multiplier of the combined standard uncertainty in order to obtain an expanded uncertainty [SOURCE: ENV 13005:1999] 3.10 designated body body which has been designated for a specific task (type approval tests and/or QA/QC activities in the field) by the competent authority in the Member States SIST EN 14212:2012

Note 1 to entry: The detection limit is calculated as 3,3x(sz/B) where sz is the standard deviation of analyser response at zero measurand concentration (see 8.4.5) and B is the slope of the calibration function [3]. 3.12 expanded uncertainty quantity defining an interval about the result of a measurement that may be expected to encompass a large fraction of the distribution of values that could reasonably be attributed to the measurand Note 1 to entry:
The fraction may be viewed as the coverage probability or level of confidence of the interval. Note 2 to entry:
To associate a specific level of confidence with the interval defined by the expanded uncertainty requires explicit or implicit assumptions regarding the probability distribution characterised by the measurement result and its combined standard uncertainty. The level of confidence that may be attributed to this interval can be known only to the extent to which such assumptions may be justified. [SOURCE: ENV 13005:1999] Note 3 to entry: For the purpose of this European Standard, the expanded uncertainty is the combined standard uncertainty multiplied by a coverage factor k=2 resulting in an interval with a level of confidence of 95 %. 3.13 fall time difference between the response time (fall) and the lag time (fall) 3.14 independent measurement individual measurement that is not influenced by a previous individual measurement by separating two individual measurements by at least four response times Note 1 to entry: The largest value of response time (rise) and response time (fall) are intended. 3.15 individual measurement measurement averaged over a time period equal to the response time of the analyser Note 1 to entry: The largest value of response time (rise) and response time (fall) are intended. Note 2 to entry: This definition differs from the meaning of the concept “individual measurement” in Directive 2008/50/EC [1]. 3.16 influence quantity quantity that is not the measurand but that affects the result of the measurement
[SOURCE: ENV 13005:1999] 3.17 interferent component of the air sample, excluding the measured constituent, that affects the output signal 3.18 lack of fit maximum deviation from the linear regression line of the average of a series of measurement results at the same concentration
These conditions include: a) the same measurement procedure; b) the same observer; c) the same analyser, used under the same conditions; d) at the same location; e) repetition over a short period of time. 3.28 reproducibility under field conditions closeness of the agreement between the results of simultaneous measurements with two analysers in ambient air carried out under the same conditions of measurement Note 1 to entry: These conditions are called field reproducibility conditions and include: a) the same measurement procedure; b) two identical analysers, used under the same conditions; SIST EN 14212:2012

[SOURCE: ENV 13005:1999] 3.37 surrounding temperature temperature of the air directly surrounding the analyser 3.38 total residence time sum of the residence time in the sampling system and the residence time inside the analyser 3.39 type approval decision taken by a designated body that the pattern of an analyser conforms to specified requirements
3.40 type approval test examination of two or more analysers of the same pattern which are submitted by a manufacturer to a designated body including the tests necessary for approval of the pattern SIST EN 14212:2012

perfluoro-ethylene-propylene;
MFC mass flow controller;
PTFE polytetrafluoroethylene. 5 Principle 5.1 General This standard describes the method for measurement of the concentration of sulphur dioxide in ambient air by means of ultraviolet fluorescence. The requirements, the specific components of the ultraviolet fluorescence analyser and its sampling system are described. A number of performance characteristics with associated minimum performance criteria are given for the analyser. The actual values of these performance characteristics for a specific type of analyser shall be determined in a so-called type approval test for which procedures have been described. The type approval test comprises a laboratory test and a field test. The selection of a type-approved analyser for a specific measuring task in the field is based on the calculation of the expanded uncertainty of the measurement method. In this expanded uncertainty calculation, the actual values of various performance characteristics of a type-approved analyser and the site-specific conditions at the monitoring station are taken into account (see 9.6). The expanded uncertainty of the method shall not exceed 15% for fixed measurements or 25 % for indicative measurements, as specified in Annex I of Directive 2008/50/EC [1]. Requirements and recommendations for quality assurance and quality control are given for the measurements in the field (see 9.4). 5.2 Measuring principle UV (ultraviolet) fluorescence is based on the emission of light by SO2 molecules excited by UV radiation when they return to their ground state: The first reaction step is: SO2 + hν → SO2* (1) In the second step the excited SO2* molecule returns to its ground state, emitting an energy hν’ according to the reaction: SO2* → SO2 + hν’ (UV) (2) The intensity of the fluorescence radiation is proportional to the number of SO2 molecules in the detection volume and is therefore proportional to the concentration of SO2. Therefore: 2SOckF×= (3) where F is the intensity of fluorescence radiation; SIST EN 14212:2012

The sampled air is then introduced into a reaction chamber, where it is irradiated by UV light in the wavelength range between 200 nm and 220 nm. The UV fluorescent light emitted in the wavelength range of 240 nm to 420 nm, is optically filtered and then converted to an electrical signal by a UV detector, for example, a photomultiplier tube. The response of the analyser is proportional to the number of SO2 molecules in the reaction chamber. Therefore, temperature and pressure either need to be kept constant, or, if variation of these parameters occurs, the measured values need to be corrected. The concentration of sulphur dioxide is directly measured in volume/volume units (if the analyser is calibrated using a volume/volume standard). The final results for reporting are expressed in µg/m3 using standard conversion factors (see Clause 10). 5.3 Type approval test The type approval test is based on the evaluation of performance characteristics determined under a prescribed series of tests. In this European Standard, test procedures are described for the determination of the actual values of the performance characteristics for at least two analysers in a laboratory and the same analysers in the field, operated in parallel in both cases. The type approval laboratory tests shall not include the sampling system and external data acquisition system, but shall include analyser sampling line and filter. The type approval field test may include a sampling inlet and a sampling system. However, the influence of these components on the test results shall be minimised by proper maintenance. A designated body shall perform these tests. The evaluation for type approval of an analyser is based on the calculation of the expanded uncertainty in the measuring result based on the numerical values of the tested performance characteristics and compared with a prescribed maximum uncertainty. The type approval of an analyser and subsequent QA and QC procedures provide evidence that the defined requirements concerning data quality laid out in Annex I of Directive 2008/50/EC [1] can be satisfied. Appropriate experimental evidence shall be provided by  type approval tests performed under conditions of intended use of the specified method of measurement, and  calculation of expanded uncertainty of results of measurement by reference to ENV 13005. 5.4 Field operation and quality control Prior to the installation and operation of a type-approved analyser at a monitoring station, an expanded uncertainty calculation shall be performed with the actual values of the performance, obtained during the type approval tests, and the site-specific conditions at that monitoring station. This calculation shall be used to demonstrate that the type-approved analyser meets the requirements for all applicable limit values under the actual conditions present at that specific monitoring station. After the installation of the approved analyser at the monitoring station, its correct functioning shall be tested. Requirements for quality assurance and quality control are given for the operation and maintenance of the sampling system, as well as for the analyser, to ensure that the uncertainty of subsequent measurement results obtained in the field is not compromised. SIST EN 14212:2012

6.1 General Depending on the installation of the ultraviolet fluorescence analyser at a monitoring station, a single sampling line for the analyser may be chosen. Alternatively, sampling can take place from a sampling system consisting of a common sampling inlet with a sampling manifold to which other analysers and equipment may be attached. Conditions and layout of the sampling system will contribute to the uncertainty of the measurement; to minimise this contribution to the expanded uncertainty, requirements for the sampling equipment are given in the following sub-clauses. NOTE
In Annex B, different arrangements of the sampling equipment are schematically presented. The following factors may, through decrease in the concentration of sulphur dioxide, contribute to the uncertainty of the measurement when considering the sampling as an integral part of the measurement: — loss of sulphur dioxide in the sampling system; — loss of sulphur dioxide in the particle filter. These factors are recognised to be relevant, but currently cannot be quantified for lack of appropriate assessment methods. As a consequence, the contributions of these factors are not considered in the uncertainty assessment applied in this standard. The effect of these factors is minimised through minimum requirements (see 6.3) and application of appropriate QA/QC measures (see 9.4 to 9.6) and maintenance (see 9.7). 6.2 Sampling location
The location where the ambient air shall be sampled and analysed is not specified as this depends strongly on the category of a monitoring station (such as measurements taken in e.g. a rural area or background area). Guidance and criteria on sampling points on a micro scale are given in Annex III of Directive 2008/50/EC [1]. 6.3 Sampling system 6.3.1 Construction The sampling system shall include a sampling inlet and may include the following components: — a sampling line or manifold; — a particle filter placed between the sampling line or manifold and the inlet of the analyser; — a sampling pump in case a sampling manifold is used. The sample inlet shall be constructed in such a way that ingress of rainwater into the sampling line or manifold is prevented. The sampling line or manifold shall be as short as practical to minimise the residence time.
In the case where a sampling manifold is used, an additional pump is necessary with sufficient capacity to fulfil the sampling requirements stated in the previous sub-clauses (see also 6.5 and Annex B). The material of the sample inlet as well as the sampling line or manifold can influence the composition of the sample. In practice, the best materials, such as polytetrafluoroethylene (PTFE), perfluoro-ethylene-propylene (FEP), borosilicate glass or stainless steel, shall be used. The influence of the material of the sampling inlet and line or manifold on the measured concentrations of sulphur dioxide due to losses shall be < 2,0 %.
NOTE This value can be achieved when the quality assurance and quality control requirements (see Clause 9) are followed.
The sampling line or manifold may be moderately heated to avoid condensation. Condensation may occur in the case of high ambient temperature and/or humidity. SIST EN 14212:2012

NOTE 1 The filter may be internal to the analyser (see 7.8) or external. In case the analyser contains a built-in filter, an external filter is not necessary. NOTE 2 A pore size of the filter of 5 µm usually fulfils this requirement. NOTE 3 Suitable materials for the filter housing are for example PTFE, stainless steel, or borosilicate glass.
The particle filter shall be conditioned before used in measurements. The filter shall be changed periodically depending on the dust loading at the sampling site (as indicated in 9.7). The filter housing shall be cleaned at least every six months. Overloading of the filter may cause loss of sulphur dioxide by adsorption on the particle matter and may increase the pressure drop in the sampling line. 6.3.3 Loss of sulphur dioxide Depending on the location of the particle filter, the sampling system can be contaminated by deposition of dust. This can induce losses of sulphur dioxide. The sampling system shall be cleaned (as stated in 9.4.2) with a frequency which is dependent on the site-specific conditions. 6.3.4 Conditioning The sampling system and the particle filter shall be conditioned (at initial installation and after each cleaning) to avoid temporary decreases in the measured sulphur dioxide concentrations by sampling ambient air for a period of at least 30 min at the nominal sample flow rate. Conditioning may also be done in the laboratory before installation. These conditioning periods shall not be included in the calculation of the availability of the analyser during the type approval test (8.5.7).
NOTE Conditioning during field operation is considered a part of normal maintenance. Consequently, the concentrations measured during conditioning need not be included in the calculation of data capture, and hourly, daily and annual averages. 6.4 Control and regulation of sample flow rate The sample flow rate into the analyser shall be maintained within the specifications of the manufacturer of the analyser.
NOTE The flow rate into the ultraviolet fluorescence analyser is usually controlled by means of restrictors. 6.5 Sampling pump for the manifold When a sampling manifold is used, a pump (or similar device, e.g. a blower) is necessary for sampling ambient air and suction of the sampled air through the sampling manifold. The inlet of the sampling pump for the sampling manifold shall be located at the end of the sampling manifold (see Annex B). The sampling pump shall have sufficient rating to ensure that all analysers connected to the manifold are supplied with the required amount of air and to ensure that the residence time is ≤ 5 s. To verify functioning of this pump, it is recommended to install a flow alarm system. An example of a sampling manifold is given in Annex B.
The influence of the pressure drop induced by the manifold sampling pump on the measured concentration shall be ≤ 1,0 %. SIST EN 14212:2012

A UV fluorescence analyser consists of the principal components which are described in 7.2 to 7.6. 7.2 Selective traps for interfering agents One or more selective traps shall be used before the fluorescence cell to remove interfering gases such as aromatic hydrocarbons. These selective traps shall not retain any SO2, and shall be replaced regularly in accordance with the manufacturer's instructions. If high concentrations of H2S are expected in the ambient air, a selective scrubber should be used. 7.3 Optical assembly The optical assembly consists of a UV lamp, a fluorescence cell, a reference sensor and a UV detector.
The UV lamp emission may be pulsed electronically or mechanically in order to enable synchronous detection and amplification of the signal. The lamp shall have a stabilised power supply to ensure a stable emission of light. An optical filter is used to restrict the wavelengths to a range which allows excitation of the sulphur dioxide molecule and minimises the interferences due to water vapour, aromatic hydrocarbons or nitrogen monoxide. This filter shall remove radiation at wavelengths longer than 600 nm, to minimise any interference produced by the UV fluorescence of unsaturated hydrocarbons, which radiate at these wavelengths. The reference sensor in the extension of the beam path behind the reaction chamber checks the constancy of the UV lamp and is used to correct the fluorescence signal or to control the UV lamp. The fluorescence cell shall be made of material inert to SO2 and UV radiation. The cell shall be heated to a constant temperature above the water vapour dew point to avoid water condensation and to minimise temperature changes. An optical trap in the fluorescence cell shall be used to prevent reflection of the UV radiation. The UV detector, for example a photomultiplier tube, detects the fluorescence light emitted by the SO2 molecules in the fluorescence cell. A selective optical filter placed in front of the photomultiplier tube reduces the signal due to scattering of incident light. The optical assembly shall be placed in a heated temperature-controlled enclosure. 7.4 Pressure measurement The output signal of the analyser is proportional to the density of SO2 (number of SO2 molecules) present in the reaction chamber and depends on the pressure in the chamber. Variations of internal pressure shall be measured and the signal corrected.
The signal shall be corrected also for external pressure and temperature fluctuations. Significant pressure variations are due to synoptic meteorological changes (up to ± 3 %) or by the altitude of the measurement site (e.g. approximately 10 % decrease in pressure for a 800 m rise in altitude). NOTE
One of the main causes of a reduced pressure in the reaction chamber is a pressure drop in the sample line.
7.5 Flow rate indicator A flow rate indicator shall be included in the analyser. SIST EN 14212:2012

7.7 Internal sulphur dioxide span source Some analysers are equipped with an internal span source. This span source shall not be used for calibration purposes. The concentrations generated by this internal span source may be used for functional tests only. 7.8 Particle filter An analyser will generally contain an internal particle filter (see 6.3.2). This filter shall be considered an integral part of the analyser for type-approval testing. 8 Type approval of ultraviolet fluorescence sulphur dioxide analysers 8.1 General
The determination of the concentration of sulphur dioxide in ambient air shall fulfil the requirement of a maximum uncertainty in the measured values, which is prescribed by Annex I of Directive 2008/50/EC (15% for fixed measurements or 25 % for indicative measurements). In order to achieve an uncertainty less than (or equal to) this required uncertainty, the ultraviolet fluorescence analyser shall fulfil all the criteria for a number of performance characteristics which are given in this standard. The values of the selected performance characteristics shall be evaluated by means of laboratory tests and field tests. By combining the values of the selected performance characteristics in the expanded uncertainty calculation, a judgement shall be made whether or not the ultraviolet fluorescence analyser meets the criterion of maximum uncertainty
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