NO2 Diffusion Tube Map

Click on any pin to obtain the site ID and up to five years’ data. Further information, including filters and data download options, is available by clicking on the inset arrow at the bottom of the map.


Nitrogen dioxide (NO2) is one of a group of gases called nitrogen oxides. Road transport is estimated to be responsible for about 50% of total emissions of nitrogen oxides, which means that NO2 levels are highest close to busy roads and in large urban areas. Gas boilers in buildings are also a source of nitrogen oxides.

There is good evidence that NO2 is harmful to health. It inflames the lining of the lungs and reduces immunity to lung infections such as bronchitis.

NO2 also reacts with hydrocarbons in the presence of sunlight to create ozone and contributes to the formation of particles.


The Local Authorities in Sussex operate a number of diffusion tube sites to monitor NO2, as these offer a relatively cheap and simple method of assessing pollution levels. Click on this link to find where diffusion tubes are currently located and up to the last 5 years of annual average NO2 levels at these locations. Please note that a ‘0’ indicates that there is no data available.

The data are taken from the Annual Status Reports on air quality produced by the Local Authorities. These reports can be found here: For further information on the assumptions and analysis of the NO2 data please refer to the relevant report.

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