We use Diffusion Tubes in order to measure levels of Nitrogen Dioxide (NO2) within the area. They are relatively cheap, easy to use, don't require any power supply and can give a good indication of air pollution levels.
The low cost allows many of them to be used, so a picture can be built up across a large area. Non-professionals such as environmental campaigners and schools are also using them because the tubes require only limited attention and are easy to operate.
Measuring Nitrogen Dioxide Using Diffusion Tubes
Under the provisions of the 1995 Environmental Act, all local authorities in England and Wales are required to assess air quality against a set of national targets for seven key pollutants. Some locations, exclusively next to very busy roads, particularly at junctions and where there are inclines on the highway and buildings close to the kerb, levels of nitrogen dioxide (NO2) may exceed the national objective.
Environmental Protection has identified these specific locations and undertakes routine monitoring for concentrations of nitrogen dioxide at the locations.
What are diffusion tubes?
The tubes are small and made of plastic with a cap at each end. Inside the top end of the tube is a metal disc coated with a substance that reacts with nitrogen dioxide to form a new chemical which remains trapped on the tube. The tube is placed vertically in a holder, usually attached to something like a lamppost or drainpipe, and the bottom cap is removed allowing air to diffuse into the tube.
The diffusion tube is left at the site with the bottom cap removed for a month. After this time the tube has the cap replaced and is taken to a laboratory for analysis. Each tube then provides an average concentration of nitrogen dioxide for that month. The monthly results are then averaged over 12 months to give an annual mean.
Diffusion tube interactive map
An interactive map showing Nitrogen Dioxide (NO2) Diffusion Tubes diffusion tube locations and annual mean nitrogen dioxide concentrations is now available for you to view online.
The map is an interactive geographical information system which allows you to view and inspect map-based information for the Dudley area. Tools are provided to allow you to zoom and pan around the map, and 'point and click' to view information about features on the map.
An interactive map showing Nitrogen Dioxide (NO2) Diffusion Tubes diffusion tube locations and annual mean nitrogen dioxide concentrations is now available for you to view online.
The map is an interactive geographical information system which allows you to view and inspect map-based information for the Dudley area. Tools are provided to allow you to zoom and pan around the map, and 'point and click' to view information about features on the map.
As part of its duty to monitor the quality of the air in Dudley, we continuously monitor, and records as 15 minute averages, the levels of a range of common pollutants at its automatic monitoring stations.
- Concentrations of Nitrogen Dioxide (NO2) and Fine Particles (PM10 ) are monitored at Central Dudley (urban background) and Colley Gate (roadside)
- Concentrations of Nitrogen Dioxide (NO2) are measured at Wordsley (Roadside)
Levels of these pollutants may be presented in terms of 'Bandings' (Low, Medium, High or Very High), with 'indices' (1 to 10) indicating the level within each band. High or very high levels can affect the elderly, asthmatic or very young. A full explanation is also available online.
Up to date information on Air Quality including the current index are available from the UK National Air Quality Information Archive.
As part of its duty to monitor the quality of the air in Dudley Metropolitan Borough, the council continuously monitors, and records as 15 minute averages, the levels of a range of common pollutants at its automatic monitoring stations.
