This document specifies a continuous measurement method for the determination of the concentration of carbon monoxide present in ambient air based on the non-dispersive infrared spectroscopic measuring principle. This document describes the performance characteristics and sets the relevant minimum criteria required to select an appropriate non-dispersive infrared spectroscopic analyser by means of type testing. 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 and requirements during sampling, calibration and quality assurance for use. NOTE 1 Additional information is specified in Annex I of Directive 2008/50/EC [1] The method is applicable to the determination of the mass concentration of carbon monoxide present in ambient air up to 100 mg/m3 of carbon monoxide. This concentration range represents the certification range for type testing. NOTE 2 Other ranges can be used depending on the levels present in ambient air. NOTE 3 When the standard is used for other purposes than for measurements required by Directive 2008/50/EC, the ranges and uncertainty requirements might not apply. The method covers the determination of ambient air concentrations of carbon monoxide in locations classified as rural areas, urban-background areas, and for sampling points influenced by traffic or industrial sources. The results are expressed in mg/m3 (at 20 °C and 101,3 kPa). NOTE 4 100 mg/m3 of CO corresponds to 86 ¼mol/mol of CO. This document contains information for different groups of users. Clause 5 to Clause 7 and Annex B, Annex C and Annex D contain general information about the principles of carbon monoxide measurement by non-dispersive infrared spectroscopic analyser and sampling equipment. Clause 8 and Annex E are specifically directed towards test houses and laboratories that perform type testing of carbon monoxide analysers. These sections contain information about: çø type testing conditions, test procedures and test requirements; çø analyser performance requirements; çø evaluation of the type testing results; çø evaluation of the uncertainty of the measurement results of the carbon monoxide analyser based on the type testing results. Clause 9 to Clause 11 and Annex F are directed towards monitoring networks performing the practical measurements of carbon monoxide in ambient air. These sections contain information about: çø initial installation of the analyser in the monitoring network and acceptance testing; çø ongoing quality assurance/quality control; çø calculation and reporting of measurement results; çø evaluation of the uncertainty of measurement results under practical monitoring conditions. The present document represents an evolution of earlier editions (EN 14626:2005 and EN 14626:2012). When equipment is procured it complies fully with the present document. NOTE 5 Type testing performed prior to the publication of this document for the purpose of demonstrating equivalence are still valid. NOTE 6 Analysers type tested prior to the publication of this document remain valid for use for regulated monitoring purposes.