7. Except insofar as otherwise provided by regulation 15(5) or (6), the minimum number of sampling points for fixed continuous measurement to assess air quality in view of compliance with the target values, long-term objectives and information and alert thresholds where continuous measurement is the sole source of information is set out in the table below.
| Population of zone (thousands) | Agglomerations (urban and suburban)(1) | Other zones (suburban and rural)(1) | Rural background |
|---|---|---|---|
(1) At least 1 station in suburban areas, where the highest exposure of the population is likely to occur. In agglomerations at least 50% of the stations should be located in suburban areas. | |||
(2) 1 station per 25,000 km2 for complex terrain is recommended. | |||
| 0—249 | 1 | 1 station/50,000 km2 as an average density over all zones in Wales(2) | |
| 250—499 | 1 | 2 | 1 station/50,000 km2 as an average density over all zones in Wales(2) |
| 500—999 | 2 | 2 | 1 station/50,000 km2 as an average density over all zones in Wales(2) |
| 1,000—1,499 | 3 | 3 | 1 station/50,000 km2 as an average density over all zones in Wales(2) |
| 1,500—1,999 | 3 | 4 | 1 station/50,000 km2 as an average density over all zones in Wales(2) |
| 2,000—2,749 | 4 | 5 | 1 station/50,000 km2 as an average density over all zones in Wales(2) |
| 2,750—3,749 | 5 | 6 | 1 station/50,000 km2 as an average density over all zones in Wales(2) |
| 3,750 or more | 1 additional station per 2 million inhabitants | 1 additional station per 2 million inhabitants | 1 station/50,000 km2 as an average density over all zones in Wales(2) |