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Map of diffusion tube sites

We use diffusion tubes to monitor air quality at over 80 locations in the borough. You can use the interactive map below to find out more about where the diffusion tubes are located, reasons for monitoring and the levels of air pollution over the last four full years. Readings are in micrograms per cubic metre. The annual objective for nitrogen dioxide (NO2) is 40 micrograms per cubic metre. During years when no monitoring took place, results are shown as n/a. The monitoring sites are reviewed and updated each year and new sites will not be shown until a full year of monitoring has been completed and ratified. 

Please note that kerbside and roadside sites generally represent worst-case situations. Because levels of nitrogen dioxide tend to decline rapidly away from the carriageway, the data is not necessarily representative of air pollution at nearby properties.

Key to map symbols

SymbolSite typeDescription
Urban background diffusion tube symbol Urban background Urban residential areas away from sources of pollution
Kerbside diffusion tube symbol Kerbside Within one metre of the kerb
Roadside diffusion tube symbol Roadside Typically one to five metres from the kerb
Suburban diffusion tube symbol Suburban Residential areas on the outskirts of towns
Industrial diffusion tube symbol Industrial Used to monitor industrial emissions
Rural diffusion tube symbol Rural Open countryside away from roads, industry and populated areas
Other diffusion tube symbol Other Specific emission sources such as car parks


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