Paragraph
England and Wales
Diffuse sources
(a)
| Population of zone (thousands) | If concentrations exceed the upper assessment thresholds | 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 threshold |
|---|---|---|---|
| 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 — this requirement shall also apply to benzene and carbon monoxide provided that it does not increase the number of sampling points. |
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.