Paragraph 1 Microscale siting of sampling points

the flow around the inlet sampling probe must be unrestricted (free in an arc of at least 270° or, for sampling points at the building line, 180°) without any obstructions affecting the airflow in the vicinity of the inlet (that is to say 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);

the inlet sampling point must be between 1.5 m (the breathing zone) and 4 m above the ground unless the station is representative of a large area and higher siting is appropriate. Any derogations must be fully documented;

the inlet probe must not be positioned in the immediate vicinity of sources in order to avoid the direct intake of emissions unmixed with ambient air;

the sampler's exhaust outlet must be positioned so that recirculation of exhaust air to the sampler inlet is avoided;

in relation to the location of traffic-orientated samplers, sampling points must be at least 25 m from the edge of major junctions and no more than 10 m from the kerbside. F2A “major junction” is a junction which interrupts the traffic flow and causes different emissions (due to vehicles stopping and starting) from the rest of the road.