# The Air Quality Limit Values (Wales) Regulations 2001, Part I: Minimum number of sampling points for fixed measurement to assess compliance with limit values for the protection of human health and alert thresholds in zones and agglomerations where fixed measurement is the sole source of information


Diffuse sources
(a) Population of agglomeration or zone (thousands)
If concentrations exceed the upper assessment threshold
If maximum concentrations are between the upper and lower assessment thresholds
For SO2 and NO2 in agglomerations where maximum concentrations are below the lower assessment thresholds
0–250
1
1
not applicable
250–499
2
1
1
500–749
2
1
1
750–999
3
1
1
1 000–1 499
4
2
1
1 500–1 999
5
2
1
2 000–2 749
6
3
2
2 750–3 749
7
3
2
3 750–4 749
8
4
2
4 750– 5 999
9
4
2
> 6 000
10
5
3
For NO2 and particulate matter: to include at least one urban-background station and one traffic-orientated station
Point sources
(b) For the assessment of pollution in the vicinity of point sources, the number of sampling points for fixed measurement should be calculated taking into account emission densities, the likely distribution patterns of ambient-air pollution and the potential exposure of the population.

---
Source: https://www.legislation.gov.uk/wsi/2001/2683/schedule/4/part/I (the official version)
Page: https://openlegislation.uk/air-quality-limit-values-wales-regulations-2001/schedule-4/part-I
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.