# The Air Quality Limit Values (Wales) Regulations 2002, Paragraph

Extent: E+W

The following data quality objectives, for allowed uncertainty of assessment methods, and of minimum time coverage and of data capture of measurement are provided to guide quality assurance programmes.
Benzene
Carbon monoxide
Fixed measurements
Uncertainty
25%
15%
Minimum data capture
90%
90%
Minimum time coverage
35% urban background and traffic sites (distributed over the year to be representative of various conditions for climate and traffic) 90% industrial sites
Indicative measurements
Uncertainty
30%
25%
Minimum data capture
90%
90%
Minimum time coverage
14% (one day’s measurement a week at random, evenly distributed over the year, or 8 weeks evenly distributed over the year)
14% (one measurement a week at random, evenly distributed over the year, or 8 weeks evenly distributed over the year)
Modelling
Uncertainty:
Eight-hour averages
50%
Annual averages
50%
Objective estimation
Uncertainty
100%
75%

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Source: https://www.legislation.gov.uk/wsi/2002/3183/schedule/5/part/I/paragraph/wrapper19n1 (the official version)
Page: https://openlegislation.uk/air-quality-limit-values-wales-regulations-2002/schedule-5/part-I/paragraph-wrapper19n1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.