This European Standard describes a standard method for determining the PM10 or PM2,5 mass concentrations of suspended particulate matter in ambient air by sampling the particulate matter on filters and weighing them by means of a balance. Measurements are performed with samplers with inlet designs as specified in Annex A, operating at a nominal flow rate of 2,3 m3/h, over a nominal sampling period of 24 h. Measurement results are expressed in µg/m3, where the volume of air is the volume at ambient conditions near the inlet at the time of sampling. The range of application of this European Standard is from approximately 1 µg/m3 (i.e. the limit of detection of the standard measurement method expressed as its uncertainty) up to 150 µg/m3 for PM10 and 120 µg/m3 for PM2,5. NOTE 1 Although the European Standard is not validated for higher concentrations, its range of application could well be extended to ambient air concentrations up to circa 200 µg/m3 when using suitable filter materials (see 5.). This European Standard describes procedures and gives requirements for the use of so-called sequential samplers, equipped with a filter changer, suitable for extended stand-alone operation. Sequential samplers are commonly used throughout the European Union for the measurement of concentrations in ambient air of PM10 or PM2,5. However, this European Standard does not exclude the use of single-filter samplers. This European Standard does not give procedures for the demonstration of equivalence of other sampler types, e. g. equipped with a different aerosol classifier and/or operating at different flow rates. Such procedures and requirements are given in detail in the "Guide to the Demonstration of Equivalence of Ambient Air Monitoring Methods". The present European Standard represents an evolution of earlier European Standards (EN 12341:1998 and EN 14907:2005) through the development of the 2,3 m3/h sampler to include sheath air cooling, the ability to cool filters after sampling, and the ability to monitor temperatures at critical points in the sampling system. It is recommended that when equipment is procured, that it complies fully with the present European Standard. However, older versions of these 2,3 m3/h samplers that do not employ sheath air cooling, the ability to cool filters after sampling, or the ability to monitor temperatures at critical points in the sampling system have a special status in terms of their use as reference samplers. Historical results obtained using these samplers will remain valid. These samplers can still be used for monitoring purposes and for equivalence trials, provided that a well justified additional allowance is made to their uncertainties. In addition, three specific sampling systems - the "long nozzle" 2,3 m3/h sampler and the 68 m3/h sampler for PM10 in EN 12341:1998, and the 30 m3/h PM2,5 inlet in EN 14907 - also have a special status in terms of their use as reference samplers. Historical results obtained using these samplers will remain valid. These samplers can still be used for monitoring purposes and for equivalence trials, provided that a well-justified additional allowance is made to their uncertainties (see Annex B).