CR 14377:2002
(Main)Air quality - Approach to uncertainty estimation for ambient air reference measurement methods
Air quality - Approach to uncertainty estimation for ambient air reference measurement methods
The Report is to provide guidance on uncertainty evaluation to CEN/TC 264 Working Group(s), who are involved in the preparation of Reference Methods to measure ambient air quality, as required by the EU Daughter Directives of the European Framework Directive on Ambient Air-quality Assessment and Management (96/62/EC)
Kakovost zraka - Pristop k ocenjevanju merilne negotovosti referenčnih merilnih metod za zunanji zrak
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-maj-2002
.DNRYRVW]UDND3ULVWRSNRFHQMHYDQMXPHULOQHQHJRWRYRVWLUHIHUHQþQLKPHULOQLK
PHWRG]D]XQDQML]UDN
Air quality - Approach to uncertainty estimation for ambient air reference measurement
methods
Ta slovenski standard je istoveten z: CR 14377:2002
ICS:
13.040.20 Kakovost okoljskega zraka Ambient atmospheres
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
CEN REPORT
CR 14377
RAPPORT CEN
CEN BERICHT
January 2002
ICS
English version
Air quality - Approach to uncertainty estimation for ambient air
reference measurement methods
This CEN Report was approved by CEN on 10 November 2001. It has been drawn up by the Technical Committee CEN/TC 264.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, 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
© 2002 CEN All rights of exploitation in any form and by any means reserved Ref. No. CR 14377:2002 E
worldwide for CEN national Members.
Contents
Foreword.4
1 Introduction .5
2 Assumptions and interpretations in this Report of the EC Air Quality Framework and Daughter
Directives.5
2.1 Annexes to the Daughter Directives .5
2.2 Definitions and interpretation of measurement uncertainty, level of confidence, and
confidence interval, within the Ambient Air Quality Daughter Directives .6
2.2.1 General.6
2.2.2 Uncertainty of measurement .6
2.2.3 Level of confidence .6
2.2.4 Relationship between confidence interval and measurement uncertainty .7
2.3 EC Terms of Reference .8
3 Approaches to uncertainty estimation .8
3.1 General.8
3.2 Guide to the Expression of Uncertainty in Measurement.9
3.3 International Standards ISO 5725 Parts 1 to 6.9
3.4 International Vocabulary of Basic and General Terms in Metrology.10
3.5 Other International Standards .10
4 Recommendations for the assessment of uncertainty of ambient air measurement methods .11
4.1 Introduction .11
4.1.1 General.11
4.1.2 Automated measurement methods.11
4.1.3 Non-automated measurement methods .12
4.1.4 Utilisation of traceable calibration standards and certified reference materials.13
4.1.5 Specification of the regime of field calibrations and QA/QC procedures.13
4.2 Consistent approach to the assessment of uncertainty in the Ambient Air Quality Daughter
Directives.13
4.2.1 General.13
4.2.2 General types of test procedures to be employed .14
4.2.3 Examples of the approach to uncertainty estimation given in this Report .18
4.2.4 Applicability of the general types of tests.18
5 Requirements for on-going quality assurance and quality control of field measurements
covered by the EC Directives .18
5.1 Overview of requirements.18
5.2 Specific requirements of the Framework Directive.18
5.3 Types of organisations involved.19
5.4 Requirement for traceability to national or international accepted standards .19
5.5 Demonstration of the competence of organisations involved with QA/QC activities .20
5.6 The role of quality assurance and quality control for the on-going field measurements.20
5.7 Procedures for the regular auditing of the performance of laboratories involved in QA/QC
activities.21
5.8 Conclusions.22
6 General philosophy for the development of future ambient air measurement methods .22
Annex A Principles of the Reference Methods prescribed in the EC Air Quality Daughter Directives .23
Annex B Data quality objectives contained in the Ambient Air Quality Daughter Directive covering
benzene and carbon monoxide .24
Annex C Reference measurement methods for the implementation of EU Air Quality Directives .25
Annex D Examples illustrating the approach specified in this Report for uncertainty estimation for
ambient air measurement methods .27
Annex E Definitions of measurement uncertainty terms used in this Report.35
Annex F Outline description of a methodology for a proficiency testing scheme which could be used
to underpin European harmonisation of ambient air quality measurements.36
Annex G Members of the Ad-hoc Group on an approach to uncertainty estimation for ambient air
measurement methods .38
Annex H Acknowledgements .39
Bibliography .40
Foreword
This Technical Report has been prepared by Technical Committee CEN/TC 264, "Air quality", the secretariat of
which is held by DIN.
This document is a working document.
This CEN Report has been prepared by an Ad-Hoc-Group of CEN/TC 264 "Air quality" in co-operation with the
European Commission’s Joint Research Centre, Ispra, Italy.
This CEN Report is an informative document.
1 Introduction
The European Framework Directive on Ambient Air-quality Assessment and Management, and its related Daughter
Directives, require measurements to be made using specified Reference Methods (given in outline in Annex A of
this Report), and the results to be reported, on specific air pollutants, with specified data quality objectives, by all
Member States within the EU. The main purpose of this CEN Report is to provide guidance to those CEN/TC 264
working groups which are involved in the preparation of Reference Methods to measure ambient air quality as
required by the EC Daughter Directives, on the uncertainty evaluation to be carried out in order to conform to these
data quality objectives. One further purpose of this Report is to emphasize the essential requirements for
appropriate quality assurance (QA) and quality control (QC) procedures in order to ensure that the ongoing field
measurements are valid – so as to ensure the EC data quality objectives continue to be met.
It is important to understand that these Daughter Directives specify the principles of the Reference Method to be
used, but they rely on the European standardisation body (CEN) to produce detailed Reference Method(s) for each
pollutant as European Standard(s), and to arrange for their publication so that they can be made available to
Member States. As noted above, the principles of these Reference Methods, which are to be used in the
implementation of the Directives, are prescribed in the relevant EC Directives. In some cases, these Methods are
specified as continuous or semi-continuous automated instruments, which comprise fully integrated systems,
usually including a sampling line and the analytical equipment. In other cases, the Reference Methods are
specified as manual or discontinuous methods, which comprise a field sampler and a separate laboratory analytical
component. In addition, it should be noted that in certain scenarios the Directives allow indicative methods to be
used, which are allowed to have poorer measurement uncertainties.
It is also a requirement of some of the Daughter Directives that Member States meet air quality limit values for a
variety of different averaging periods (covering e. g. hourly, daily, and annual averages). For some of the pollutants
specified, however, the requirement is only for annual averages.
The European Framework Directive on Ambient Air-quality, and the associated Daughter Directives, also state that
the approaches given in the Guide to the Expression of Uncertainty in Measurement published by ISO, and given in
the International Standards ISO 5725, are to be used for the estimation of the measurement uncertainties of these
Reference Methods. Both approaches are mentioned in these Directives as alternatives for the estimation of
measurement uncertainty. This Report describes, therefore, in broad terms, the methodology which should be
employed by the relevant CEN working groups for the integration of the approaches described in these documents
into European Standards, whilst still maintaining a valid overarching statistically-based methodology for determining
these measurement uncertainties.
The issues outlined above are covered in this Report. The Report was produced following consultations with an Ad-
hoc Group of experts which were convened to consider the issues. These experts are experienced in both ambient
air monitoring and in measurement uncertainty statistics. The members of this group and its Chairman are listed in
Annex G. It should be noted that all the existing working groups of CEN/TC 264, which are currently involved with
the standardisation of ambient air quality measurements, were represented on this Ad-hoc Group.
It should also be noted that Member States may use other methods, as alternatives to these Reference Methods –
provided they can demonstrate that these other methods produce results which have been shown to be equivalent
to those obtained by the relevant Reference Method. It is not, however, the remit of this Report to discuss the issue
of equivalence, or to define how it may be demonstrated.
2 Assumptions and interpretations in this Report of the EC Air Quality Framework and
Daughter Directives
2.1 Annexes to the Daughter Directives
Each of the Daughter Directives contains an Annex which specifies the data quality objectives required for the air
quality assessment for the particular pollutant species they address. These Annexes specify the ‘accuracy’ or
‘uncertainty’ that must be met by the Member States when reporting results, in order to satisfy the requirements of
the Directives. For clarity, it is assumed in this Report that the two terms accuracy and uncertainty are
synonymous, and therefore in the text of this Report reference will only be made to uncertainty, or to the
uncertainty of measurement, as defined in the Guide to the Expression of Uncertainty of Measurement (1993)
published by ISO – known hereafter in this Report as the GUM. An overview of the GUM is presented in clause 3.2
of this Report.
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