How we monitor air quality
South Oxfordshire District Council has been monitoring air quality since 1997. We currently monitor nitrogen dioxide using diffusion tubes at numerous locations across the district, and three continuous air quality analysers installed in the High Street, Wallingford; Duke Street, Henley-on-Thames and Couching Street, Watlington.
How we monitor air quality
Diffusion tubes
Diffusion tubes are passive samplers, consisting of small plastic tubes which are mounted on lampposts, traffic signs and buildings. During sampling, one end is open and the other contains gauze, impregnated with a substance which absorbs nitrogen dioxide. We leave the tubes exposed for one month, then seal and send them off for laboratory analysis. Although they cannot be used to provide up to the minute pollution levels, they are relatively inexpensive and can give indications of long term trends. Go here for diffusion tube data and their locations .
Continuous air quality analysers
These electronic analysers pump in air from the street and make use of a chemical process known as chemiluminescence to continuously measure the concentration of nitrogen dioxide. The analyser logs the data, then downloads it to a computer for analysis. This can provide real-time data , and enables us to look at the concentrations of nitrogen dioxide over varying time periods. Both annual and hourly mean concentrations are needed to determine whether or not government air quality objectives have been met. Go here for more information about our air quality analysers .
Last reviewed: 27 - 01 - 2011