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Practical Guidance: NO2 Diffusion Tubes for LAQM


Defra and the Devolved Administrations commissioned a Working Group, comprising representation from Defra and the Devolved Administrations, laboratories, the Health and Safety Laboratory, the Environment Agency, the Scottish Environment Protection Agency (SEPA) and other stakeholders, aimed at harmonising the methodology used in preparing, utilising and analysing diffusion tubes.

The Working Group’s report was published in February 2008 and includes guidance on all aspects of diffusion tube use in the context of LAQM: tube preparation, handling, use, analysis and calculation of results. It is recommended that Local Authorities refer to this more detailed guidance, some of which is summarised in the Technical Guidance LAQM.TG(22).

The following were agreed as the aims and objectives of the Working Group: “To investigate current practice in design, preparation and analysis of diffusion tube samplers for nitrogen dioxide, and to recommend changes as appropriate to improve in particular precision of measurement through harmonisation of preparation and analysis methods and tube design”.

The Working Group has therefore produced this document, which aims to provide practical guidance both for laboratories working with diffusion tubes, and those who make use of them – in particular, local authorities using diffusion tubes for Local Air Quality Management purposes. This guidance attempts to harmonise the different steps in the UK diffusion tube methodology based on current knowledge of best practice.


Diffusion Tubes for Ambient NO2 Monitoring: Practical Guidance

Released: February 2008 (PDF, 1.34 MB, 47 pages)


It should be noted that this document does not constitute a formal standard method. However, in the absence of an international, European or UK standard method for diffusion tubes, this guidance is intended to form the basis of harmonisation of methods within the UK, until such time as a standard method is developed. Defra and the Devolved Administrations will expect laboratories to implement this guidance for diffusion tubes used by local authorities for Local Air Quality Management.

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