CEN/TC 264/WG 15 - Ambient Air - Reference gravimetric measurement method and equivalence procedure for the determination of the PM 2,5 micronmillimeters mass fraction of suspended particulate matter.

This European Standard describes a standard method for determining the PM10 or PM2,5 mass concentrations of suspendedparticulate 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 atambient conditions near the inlet at the time of sampling.
The range of application of this European Standard is for 24 h measurements from approximately 1 μg/m3 (i.e. the limit of detection ofthe standard measurement method expressed as its uncertainty) up to 150 μg/m3 for PM10 and 120 μg/m3 for PM2,5.
This European Standard describes procedures and gives requirements for the testing and use of so-called sequential samplers,equipped with a filter changer, suitable for extended stand-alone operation. Sequential samplers are commonly used throughout theEuropean Union for the measurement of concentrations in ambient air of PM10 or PM2,5. However, this European Standard does notexclude the use of single-filter samplers.
This European Standard represents an evolution of earlier European Standards (EN 12341:1998 and 2014, EN 14907:2005). Newequipment procured shall comply fully with this European Standard.
Older versions of these samplers, including those described in EN 12341:2014 Annex B, have a special status in terms of their use. These samplers can still be used for monitoring purposes and for ongoing quality control, provided that a well justified additionalallowance is made to their uncertainties
This European Standard also provides guidance for the selection and testing of filters with the aim of reducing the measurementuncertainty of the results obtained when applying this European Standard.

In order to be in compliance with EU Air Quality Directive requirements, the reference methods given in the Directive 2008/50/EC [1] for the measurement of mass concentrations of particulate matter are not commonly used for operation in routine monitoring networks. These networks usually apply automated continuous measurement systems (AMS), such as those based on the use of oscillating microbalances, ß-ray attenuation, or in-situ optical methods. Such AMS are typically capable of producing 24-hour average measurement values over a measurement range up to 1 000 µg/m3 and 1-hour average measurement values up to 10 000 µg/m3, if applicable, where the volume of air is the volume at ambient conditions near the inlet at the time of sampling.
The 1-hour average values may be used for:
a)   direct information of the public;
b)   aggregation to produce daily or yearly average concentration values for regulatory reporting purposes.
Directive 2008/50/EC allows the use of such systems after demonstration of equivalence with the reference method, i.e. after demonstration that these systems meet the Data Quality Objectives for continuous measurements. Guidelines for the demonstration of equivalence are given in Reference [2].
This European Standard lays down the minimum performance requirements and test procedures for the type approval of appropriate AMS for particulate matter. This includes the evaluation of its equivalence with the reference method as laid down in Directive 2008/50/EC.
Further, this European Standard describes minimum requirements for ongoing quality assurance – quality control (QA/QC) of AMS deployed in the field. These requirements are necessary to ensure that uncertainties of measured concentrations are kept within the required limits during extended periods of continuous monitoring in the field, and include procedures for maintenance, calibration and control checks.
Additional procedures are described that determine whether an instrument’s equivalence to the reference method is maintained through possible pollution climate changes, over periods longer than five years.
Lastly, this European Standard describes harmonized requirements and procedures for the treatment and validation of raw measurement data that are used for the assembly of daily or yearly average concentration values. Experience with existing methods for data treatment and validation – for similar AMS – has shown that the different ways of data treatment and validation applied may lead to significant differences in reported results for similar datasets [3].
When the European Standard is used for purposes other than measurements required by Directive 2008/50/EC, the range and uncertainty requirements may not apply.
This European Standard contains information for different groups of users.
Clauses 5 and 6 and Annex A contain general information about the principles of automated continuous measurement systems for particulate matter, and relevant equipment.
Clause 7 and Annexes B and C are specifically directed towards test houses and laboratories that perform type-approval testing of automated continuous measurement systems for particulate matter. These clauses contain information about:
c)   type-approval test conditions, test procedures and test requirements;
d)   system performance requirements;
e)   evaluation of the type-approval test results;
f)   evaluation of the uncertainty of the measurement results of the automated continuous measurement systems for particulate matter based on the type-approval test results.
Clauses 8 to 11 are aimed at monitoring networks performing the practical measurements of particulate matter in ambient air. These clauses contain information about:
g)   initial installation of the system in the monitoring network and acceptance testing;
h)   ongoing quality assurance/quality control;
i)   on-going verification of suitability;
j)   treatment, validation and reporting of measurement results.

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 5.1.4).
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 [11] and for automated continuous PM monitors (see CEN/TS 16450:2013).
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 constraints on the filter temperature during and after sampling and the ability to monitor temperatures at critical points in the sampling system. It is recommended that when equipment is procured 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 (see Annex B).
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 14907:2005  - 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).
Other sampling systems, as described in Annex B of this European Standard, can be used provided that a well justified additional allowance is made to their uncertainties as derived from equivalence tests.
NOTE 2   By evaluating existing data it has been shown that these samplers give results for PM10 and PM2,5 that are equivalent to those obtained by application of this European Standard. Results are shown in Annex B.
This European Standard also provides guidance for the selection and testing of filters with the aim of reducing the measurement uncertainty of the results obtained when applying this European Standard.

In order to be in compliance with EU Air Quality Directive requirements [1], the reference methods given in the Directive for the measurement of mass concentrations of particulate matter are not commonly used for operation in routine monitoring networks. These networks usually apply automated continuous measurement systems (AMS), such as those based on the use of oscillating microbalances or ß-ray attenuation, and on in-situ optical methods. Such AMS are typically capable of producing 24-hour average measurement values over a measurement range up to 1 000 µg/m3 and 1-hour average measurement values up to 10 000 µg/m3, if applicable, where the volume of air is the volume at ambient conditions near the inlet at the time of sampling.
The 1-hour average values may be used for:
- direct information of the public;
- aggregation to produce daily or yearly average concentration values for regulatory reporting purposes.
EU Air Quality Directive 2008/50/EC [1] allows the use of such systems after demonstration of equivalence with the reference method, i.e., after demonstration that these systems meet the Data Quality Objectives for continuous measurements. Guidelines for the demonstration of equivalence are given in Reference [2].
This Technical Specification lays down the minimum performance requirements and test procedures for the selection of appropriate AMS for particulate matter (type approval). This includes the evaluation of its equivalence with the reference method.
Further, this Technical Specification describes minimum requirements for ongoing quality assurance – quality control (QA/QC) of AMS deployed in the field. These requirements are necessary to ensure that uncertainties of measured concentrations are kept within the required limits during extended periods of continuous monitoring in the field, and include procedures for maintenance, calibration and control checks.
Additional procedures are described that determine whether an instrument’s equivalence to the reference method is maintained through possible pollution climate changes, over periods longer than five years.
Lastly, this Technical Specification describes requirements and procedures for the treatment and validation of raw measurement data that are to be used for the assembly of daily or yearly average concentration values. Experiences with existing methods for data treatment and validation – for similar AMS – have learned that the different ways of data treatment and validation applied may lead to significant differences in reported results for similar datasets [3].
When the Technical Specification is used for other purposes than the EU Directive, the range and uncertainty requirements may not apply.
This Technical Specification contains information for different groups of users.
Clauses 5 and 6 and Annex A contain general information about the principles of automated continuous measurement systems for particulate matter, and relevant equipment.
Clause 7 and Annexes B and C are specifically directed towards test houses and laboratories that perform type-approval testing of automated continuous measurement systems for particulate matter. These clauses contain information about:
- type-approval test conditions, test procedures and test requirements;
- system performance requirements;
- evaluation of the type-approval test results;
- evaluation of the uncertainty of the measurement results of the automated continuous measurement systems for particulate matter based on the type-approval test results.
Clauses 8 to 11 are directed towards monitoring networks performing the practical measurements of particulate matter in ambient air. These clauses contain information about:
- initial installation of the system in the monitoring network and acceptance testing;
- ongoing quality assurance/quality control;
- verification of equivalence;
- treatment, validation and reporting of measurement results.

This European Standard describes a standard method for determining the PM2,5 mass concentration of suspended particulate matter in ambient air by sampling the particulate matter on filters and weighing them by means of a balance.
Measurements are made over a sampling period of about 24 h, and in line with the Directive, are expressed as 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 the standard is from 1 µg/m3 (i.e. the limit of detection of the standard measurement method expressed as its uncertainty) up to 120 µg/m3 (i.e. the maximum concentration level observed during the field study undertaken by CEN/TC 264/WG 15 to validate the standard).
NOTE    Although the standard is not validated for concentrations over 120 µg/m3, its range of application could well be extended to commonly encountered ambient concentrations up to circa 200 µg/m3 when using glass or quartz fibre filters. At these high concentrations and particulate mass loadings no filter clogging is to be expected. Also the flow rate can be easily maintained at the nominal setting.
The equivalence procedure in Annex A specifies two approaches, depending on whether the candidate method differs slightly or fundamentally from the standard method.
In the former case, involving only slight differences from the standard method ("variations on a theme") Annex A provides a restricted procedure to compare only the pertinent differences, instead of a full field test. This part of the annex serves to give practical guidance for determining equivalence for measurement methods commonly used in monitoring networks, and includes examples of common variations to the standard method, such as different filter storing or conditioning procedures and the variation of the standard method for the application as automated filter changer.