# The Air Quality Standards (Wales) Regulations 2007, Part 1: Alert thresholds for nitrogen dioxide and sulphur dioxide


Nitrogen dioxide
400 μg/m3 measured over three consecutive hours at locations representative of air quality over at least 100 km2 or an entire zone or agglomeration, whichever is the smaller
Sulphur dioxide
500 μg/m3 measured over three consecutive hours at locations representative of air quality over at least 100 km2 or an entire zone or agglomeration, whichever is the smaller

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Source: https://www.legislation.gov.uk/wsi/2007/717/schedule/3/part/1 (the official version)
Page: https://openlegislation.uk/air-quality-standards-wales-regulations-2007/schedule-3/part-1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.