The Air Quality Standards (Wales) Regulations 2007

PART 2 Macroscale siting for Group B pollutants

7.  The sites of sampling points should be selected in such a way as to provide data on—

(a) the areas within zones where the population is likely to be directly or indirectly exposed to the highest concentrations averaged over a calendar year;

(b) concentrations in other areas within zones which are representative of the exposure of the general population;

(c) deposition rates representing the indirect exposure of the population through the food chain.

8.  Sampling points should in general be sited so as to avoid measuring very small micro-environments in their immediate vicinity. As a guideline, a sampling point should be representative of air quality in surrounding areas of no less than 200 m² at traffic-orientated sites, at least 250 m ×; 250 m at industrial sites, where feasible, and several square kilometres at urban-background sites.

9.  Where the objective is to assess background levels the sampling site should not be influenced by agglomerations or industrial sites in its vicinity, i.e. sites closer than a few kilometres.

10.  Where contributions from industrial sources are to be assessed, at least one sampling point must be installed downwind of the source in the nearest residential area. Where the background concentration is not known, an additional sampling point must be situated within the main wind direction. In particular, where regulation 9(1)(a) applies, the sampling points should be sited such that the application of the measures referred to at regulation 7(2)(b) can be monitored.

11.  Sampling points should also, where possible, be representative of similar locations not in their immediate vicinity. Where appropriate, they should be co-located with sampling points for PM₁₀.