Diffusion tubes


Guidance and tools relating to NO2 diffusion tubes are provided in this section using the links on the menu on the left hand side.

The National Diffusion Tube Bias Spreadsheet for 2021 is now available. Click here for more information.

Diffusive samplers (as described in Technical Guidance LAQM.TG(16)) are widely used for indicative monitoring of ambient nitrogen dioxide (NO2) in the context of Review and Assessment. Diffusion tubes are particularly useful:

  • when simple, indicative techniques will suffice;
  • to give an indication of longer-term average NO2 concentrations;
  • for indicative comparison with the Air Quality Strategy Objectives based on the annual mean;
  • for highlighting areas of high NO2 concentration; and
  • where installation of an automatic analyser is not feasible

They are useful for identifying areas of high NO2 concentration, particularly when dealing with sources such as traffic emissions, which do not change much from day to day.

The monitoring calendars providing recommended exposure dates for diffusion tubes are available here.

Please also see the FAQs section on Diffusion Tubes here.

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