Microscale siting of sampling points
9. Insofar as is practicable, sampling points shall be situated in accordance with the following criteria—
(a)the flow around the inlet sampling probe must be unrestricted (free in an arc of at least 270o) without any obstructions affecting the airflow in the vicinity of the sampler and the inlet sampling probe must normally be some metres away from buildings, balconies, trees and other obstacles and at least 0.5 m from the nearest building in the case of sampling points representing air quality at the building line;
(b)in general, the inlet sampling point shall be between 1.5 m (the breathing zone) and 4 m above the ground. However, higher positions (up to 8 m) may be necessary in some circumstances. Higher siting may also be appropriate if the station is representative of a large area;
(c)the inlet probe shall not be positioned in the immediate vicinity of sources in order to avoid the direct intake of emissions unmixed with ambient air;
(d)the sampler’s exhaust outlet must be positioned so that recirculation of exhaust air to the sampler inlet is avoided;
(e)in relation to the location of traffic-orientated samplers, sampling points must be at least 25 m from the edge of major junctions and at least 10 m from the kerbside.