(a)Protection of human health
Sampling points directed at the protection of human health should be sited:
(i)to provide data on the areas within zones where the highest concentrations occur to which the population is likely to be directly or indirectly exposed for a period which is significant in relation to the averaging period of the limit value(s);
(ii)to provide data on levels in other areas within the zones which are representative of the exposure of the general population.
Sampling points should in general be sited to avoid measuring very small micro-environments in their immediate vicinity. As a guideline, a sampling point should be sited to be representative of air quality in a surrounding area of no less than 200 m2 at traffic-orientated sites and of several square kilometres at urban-background sites.
Sampling points should also, where possible, be representative of similar locations not in their immediate vicinity.
Account should be taken of the need to locate sampling points on islands, where that is necessary for the protection of human health.
(b)Protection of ecosystems and vegetation
Sampling points targeted at the protection of ecosystems or vegetation should be sited more than 20 km from agglomerations or more than 5 km from other built-up areas, industrial installations or motorways. As a guideline, a sampling point should be sited to be representative of air quality in a surrounding area of at least 1000 km2. A sampling point may be sited at a lesser distance or to be representative of air quality in a less extended area, taking account of geographical conditions.
Account should be taken of the need to assess air quality on islands.