The Air Quality Standards Regulations (Northern Ireland) 2007

PART 4 Microscale siting

13.  The following guidelines should be met as far as practicable—

(a) the flow around the inlet sampling probe shall be unrestricted, (and, for ozone sampling, free in an arc of at least 270°) without any obstructions affecting the airflow in the vicinity of the sampler—

(i) in the case of Group A and Group B pollutants, the inlet sampling probe shall 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; and

(ii) in the case of ozone, the inlet sampling probe shall be away from buildings, balconies, trees and other obstacles by more than twice the height the obstacle protrudes above the sampler;

(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 and (for ozone sampling) in wooded areas. 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 shall be positioned so that recirculation of exhaust air to the sampler inlet is avoided;

(e) in relation to the location of traffic orientated samplers for Group A and Group B pollutants—

(i) sampling points shall be at least 25 m from the edge of major junctions and at least 4 m from the centre of the nearest traffic lane;

(ii) for nitrogen dioxide and carbon monoxide, inlets shall be no more than 5 m from the kerbside; and

(iii) for PM₁₀, lead, benzene and Group B pollutants, inlets shall be sited so as to be representative of air quality near to the building line;

(f) for ozone, the inlet probe shall be positioned well away from such sources as furnaces and incineration flues and more than 10m from the nearest road, with distance increasing as a function of traffic intensity; and

(g) for deposition measurements in rural background areas as respects Group B pollutants and other pollutants falling within regulations 19 and 20, the European Monitoring and Evaluation of Pollutants guidelines and criteria shall be applied as far as practicable.

14.  The following factors may also be taken into account—

(a) interfering sources;

(b) security;

(c) access;

(d) availability of electrical power and telephone communications;

(e) visibility of the site in relation to its surroundings;

(f) safety of public and operators;

(g) the desirability of co-locating sampling points for different pollutants;

(h) planning requirements.