Demonstration of Equivalence of PM Monitoring Methods

Requirements of the Ambient Air Quality Directive

The CEN Standard Method for PM analysers describes both the design of the analyser (the Reference Method), as well as the operating methodology for gravimetric samplers. However, due to the time required to process and report the results, sampler data cannot be used for rapid public information purposes. The Directive therefore allows Member States to use alternative techniques where "equivalence" with the reference method can be proven in accordance with specific requirements. A procedure for demonstration of equivalence has been defined by the EU Commission, primarily to ensure measurements with near real time analysers fulfil the requirements of the data quality objectives (DQO) defined in the EU Air Quality Directive 2008/50/EC. This procedure is defined in the 2010 Guide to Demonstration of Equivalence (GDE).

UK Work Programme on Equivalence

The UK has spearheaded an extensive study into the relationships between measurements of a range of automatic analysers and gravimetric samplers with the Reference Method. The results of this initial, pioneering test programme can be found in the following reports:

Following this initial study, instrument manufacturers have continued to submit methods for equivalence tests and declaration of suitability. The current status of measurement methods is set out in the Table on the Certification: MCERTS from UK Particulate Matter page.

UK Approval of Equivalence

The responsibility for declaring measurement methods equivalent for use in the UK lies with Defra as the Competent Authority. Many manufacturers have also, but separately, opted to get UK type approval with the Continuous Ambient Measurement Systems (CAMS) performance standard through the MCERTS scheme which mirrors the requirements of the 2010 Guide to Demonstration of Equivalence. Defra has developed in partnership with the Environment Agency a new and additional level of certification through the MCERTS scheme which requires the instruments to demonstrate equivalence in a representative particulate matter pollution climate for the UK. This certification is called "MCERTS for Particulate Matter UK".

Other methods have been MCERTS certified for the Performance Standard for Indicative Ambient Particular Matter which it should be noted, is entirely different to the CAMS standard. Measurements from indicative MCERTS analysers carry a higher measure of uncertainty than reference equivalent analysers. Indicative analysers may not fulfil the requirements of the EU Data Quality Objectives.