# The Air Quality Limit Values (Wales) Regulations 2001, Paragraph 1.1: Limit values for sulphur dioxide


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
350 μg/m3, not to be exceeded more than 24 times a calendar year
150 μg/m3 (43%) on 19 July 1999, reducing on 1 January 2001 and every 12 months thereafter by equal annual percentages to reach 0% by 1 January 2005
1 January 2005
2 Daily limit value for the protection of human health
24 hours
125 μg/m3, not to be exceeded more than 3 times a calendar year
None
1 January 2005
3 Limit value for the protection of ecosystems
Calendar year and winter (1 October to 31 March)
20 μg/m3
None
19 July 2001

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Source: https://www.legislation.gov.uk/wsi/2001/2683/schedule/1/paragraph/1.1 (the official version)
Page: https://openlegislation.uk/air-quality-limit-values-wales-regulations-2001/schedule-1/paragraph-1.1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.