This European Standard specifies a continuous measurement method for the determination of the concentration of sulphur dioxide present in ambient air based on the ultraviolet fluorescence measuring principle. This standard describes the performance characteristics and sets the relevant minimum criteria required to select an appropriate ultraviolet fluorescence analyser by means of type approval tests. It also includes the evaluation of the suitability of an analyser for use in a specific fixed site so as to meet the data quality requirements as specified in Annex I of Directive 2008/50/EC and requirements during sampling, calibration and quality assurance for use. The method is applicable to the determination of the mass concentration of sulphur dioxide present in ambient air up to 1000 µg/m 3. This concentration range represents the certification range for SO2 for the type approval test. NOTE 1 Other ranges may be used depending on the levels present in ambient air. 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/m 3 (at 20 °C and 101,3 kPa). NOTE 31000 µg/m 3 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.