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PART 4 Microscale siting

13.  The following guidelines shall 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.

PART 5 Documentation and review of site selection

15.  The site-selection procedures shall be fully documented at the classification stage by such means as compass-point photographs of the surrounding area and a detailed map. Sites shall be reviewed at regular intervals with repeated documentation to ensure that selection criteria remain valid over time.

16.  For ozone, this requires screening and interpretation of the monitoring data in the context of the meteorological and photochemical processes affecting the ozone concentrations measured at the respective site.

Regulation 15(6)(b)Regulation 16(1)

SCHEDULE 7 Requirements for assessment methods other than fixed measurement

PART 1 Group A pollutants

1.  The following information shall be compiled for zones within which sources other than fixed measurement are employed to supplement information from fixed measurement or as the sole means of air quality assessment—

(a) a description of assessment activities carried out;

(b) the specific methods used, with references to descriptions of the method;

(c) the sources of data and information;

(d) a description of results, including information relating to—

(i) accuracies;

(ii) in particular, the extent of any area or, if relevant, the length of road within the zone over which concentrations exceed the limit value or, as may be, the limit value plus applicable margin of tolerance; and

(iii) any area within which concentrations exceed the upper assessment threshold or the lower assessment threshold; and

(e) for limit values the object of which is the protection of human health, the population potentially exposed to concentrations in excess of the limit value.

2.  Where possible maps shall be compiled showing concentration distributions within each zone.

PART 2 Group B pollutants

Requirements for air quality models

3.  Where an air quality model is used for assessment, references to descriptions of the model and information on the uncertainty shall be compiled. The uncertainty for modelling is defined as the maximum deviation of the measured and calculated concentration levels, over a full year, without taking into account the timing of the events.

Requirements for objective estimation techniques

4.  Where objective estimation techniques are used, the uncertainty shall not exceed 100%.

Standardisation

5.  For substances to be analysed in the PM₁₀ fraction, the sampling volume shall refer to ambient conditions.