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How is air pollution measured?

There are two distinct types of air pollution monitoring generally in use - non-automatic and automatic.

Non-automatic monitoring methods are often cheaper and easier to operate, and generally involve placing a special tube in a location for 2-4 weeks and then sending it to a laboratory for chemical analysis. This method only provides one value for the whole of time it was in place, and there is also a delay in producing the measurements.

Automatic methods are more accurate and have better time resolution, typically providing a reading every 15 minutes. Automatic methods involve the use of electronic recording and analysis.

The London Air Quality Network consists of automatic equipment in fixed cabins. This allows us to obtain a long history of measurement with the same equipment at the same location.

Air is drawn into specialist equipment from a chosen location at about the breathing height. Data is then downloaded to the Environmental Research Group (ERG) at Imperial College London, before being disseminated to the public in many different ways. The network uses reference equipment that is maintained to strict quality procedures to ensure reliable results.

Recent advances in small sensors offer of exciting opportunities for citizen science and for people to measure their own pollution exposure. However these sensors are normally based on technologies that were first developed for workplaces and they can give misleading results when used to measure the pollution that we experience in everyday London .

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