Eastleigh Borough Council currently monitor nitrogen dioxide (NO2) concentrations at 41 sites across the borough using diffusion tubes.

Diffusion tubes are widely used for indicative monitoring of ambient 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 also 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 data is available to download here