# Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe, Division A: Criteria

Extent: E+W+S+N.I.

Without prejudice to Annex I, the following criteria shall be used for checking validity when aggregating data and calculating statistical parameters:
The requirements for the calculation of annual mean do not include losses of data due to the regular calibration or the normal maintenance of the instrumentation.
Parameter
Required proportion of valid data
One hour values
75 % (i.e. 45 minutes)
Eight hours values
75 % of values (i.e. 6 hours)
Maximum daily 8-hour mean
75 % of the hourly running eight hour averages (i.e. 18 eight hour averages per day)
24-hour values
75 % of the hourly averages (i.e. at least 18 hour values)
Annual mean
90 % of the one hour values or (if not available) 24-hour values over the year

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Source: https://www.legislation.gov.uk/eudr/2008/50/annex/XI/division/A (the official version)
Page: https://openlegislation.uk/eu-directive-2008-50/annex-XI/division-A
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.