# The Air Quality Limit Values (Wales) Regulations 2001, Paragraph 2.1: Limit values for nitrogen dioxide and oxides of nitrogen


Averaging Period
Limit value
Margin of tolerance
Date by which limit value is to be met
1 Hourly limit value for the protection of human health
1 hour
200μg/m3 NO2not to be exceeded more than 18 times a calendar year
50% on 19 July 1999, reducing on 1 January 2001 and every 12 months thereafter by equal annual percentages to reach 0% by 1 January 2010
1 January 2010
2 Annual limit value for the protection of human health
Calendar year
40 μg/m3NO2
50% on 19 July 1999 reducing on 1 January 2001 and every 12 months thereafter by equal annual percentages to reach 0% by 1 January 2010
1 January 2010
3 Annual limit value for the protection of vegetation
Calendar year
30 μg/m3 NOx
None
19 July 2001

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Source: https://www.legislation.gov.uk/wsi/2001/2683/schedule/1/paragraph/2.1 (the official version)
Page: https://openlegislation.uk/air-quality-limit-values-wales-regulations-2001/schedule-1/paragraph-2.1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.