Indicative nitrogen dioxide (NO2) concentrations are determined using passive diffusion tube samplers. This method is useful but is ‘indicative’ only. This means that it only gives us an estimate of longer-term average NO2 concentrations. The results from the national air quality monitoring network are obtained using the European Committee for Standardisation’s approved methods (reference methods) – this method accurately and precisely measures EU yearly limits of NO2.

A diffusion tube consists of a small plastic tube which contains a chemical reagent that absorbs NO2 directly from air. Diffusion tubes are inexpensive and can be positioned over a wider area to get a better picture of NO2 levels within a local area.

The map below displays the indicative concentration of NO2 measured for the selected year. We measure NO2 in micrograms per cubic metre – µg/m3. High levels are 40 µg/m3 or over and low levels are under this level.

The diffusion tube sampling was carried out in conjunction with Cork City Council, Dublin City Council, Galway City Council, Limerick City and County Council and Waterford City and County Council.