# The Air Quality Standards Regulations 2010, Paragraph 3


Sampling points in urban background locations must be located so that their pollution level is influenced by the combined contribution from all sources upwind of the station. The pollution level should not be dominated by a single source unless such a situation is typical for a larger urban area. Those sampling points must, as a general rule, be representative for several square kilometres.

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Source: https://www.legislation.gov.uk/uksi/2010/1001/schedule/1/part/2/paragraph/3 (the official version)
Page: https://openlegislation.uk/air-quality-standards-regulations-2010/schedule-1/part-2/paragraph-3
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.