QA QC Framework

As part of their provision of support to Local Authorities for air quality management, Defra and the Devolved Administrations provide a set of centralised QA/QC services, to assist Local Authorities using diffusive samplers for monitoring of ambient nitrogen dioxide (NO2) concentration, as part of their Local Air Quality Management process.

This is aimed at the analytical laboratories that supply and analyse the diffusion tubes, and currently comprises:

  • Promotion of the independent AIR-PT scheme, operated by LGC Standards and supported by the Health and Safety Laboratory, with yearly assessment against agreed performance criteria. AIR-PT combines two long running PT schemes: LGC Standards STACKS PT scheme and HSL Workplace Analysis Scheme for Proficiency (WASP) PT scheme. For more information about the AIR-PT scheme, please click here.
  • Operation of a field intercomparison exercise, in which diffusion tubes are co-located with an automatic analyser: from January 2006 this is at a roadside site.
  • Provision of quality control standard solutions, free of charge to laboratories that prepare and analyse NO2 diffusion tubes used by Local Authorities for LAQM purposes.

Summaries of participating laboratories' performance in the AIR-PT/WASP scheme over the preceding months, prepared by LGC/BV/NPL, are available by clicking on the links below:

Investigation of the Effects of Harmonising Diffusion Tube Methodology

The report (downloadable here) investigates whether harmonisation of preparation and analysis methods for NO2 diffusion tubes has reduced inter-laboratory variation in performance of NO2 diffusion tubes in the UK.

The following report covers an investigation into the effects of harmonising the NO2 diffusion tube methodology by the previous contractor up to 2010. It refers to a rolling performance indicator (RPI) criterion in the discussion of the WASP data. Following a consultation with the participating laboratories HSL has decided to return to the z-scoring system in the future (2011 onwards), and this time will include the percentage of results submitted, which are determined to be satisfactory, based upon a z-score of < ± 2.


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