5. Criteria for determining the spatial representativeness area of sampling points

(a)

the geographical area may include non-contiguous domains but shall be limited in its extension by the borders of the zone under consideration;

(b)

if assessed via modelling applications, a fit-for-purpose modelling system shall be used and modelled concentrations shall be used at location of the sampling point to prevent systematic model-measurement biases from distorting the assessment;

(c)

other metrics than absolute concentrations may be considered, e.g. percentiles;

(d)

the tolerance levels and possible cut-offs for the different pollutants may vary depending on the characteristics of the sampling point;

(e)

the annual average of the observed pollutant concentration shall be used as the air quality metric for a specific year.

(a)

the flow around the sampling point inlet shall be unrestricted (in general free in an arc of at least 270o, or, for sampling points at the building line, of at least 180o) without any obstructions affecting the airflow in the vicinity of the inlet (at least 1,5 m 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 sampling point inlet shall be between 0,5 m (the breathing zone) and 4 m above the ground; higher siting may also be appropriate if the sampling point is located in a background location; the decision to apply such higher siting shall be fully documented;

(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 to which members of the public are unlikely to be exposed;

(d)

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

(e)

for all pollutants, sampling probes focused on measuring contributions from road traffic shall be at least 25 m from the edge of major junctions and no more than 10 m from the kerbside; for the purposes of this point, a ‘kerbside’ means the line that separates motorised traffic from other areas; a ‘major junction’ means a junction which interrupts the traffic flow and causes different emissions (stop&go) from the rest of the road;

(f)

for the deposition measurements in background locations, the guidelines and criteria of EMEP shall apply;

(g)

for ozone measurement, Member States shall ensure that the sampling point is positioned well away from sources such as furnaces and incineration flues, and more than 10 m from the nearest road, with distance increasing as a function of traffic intensity;

(h)

the following factors may also be taken into account: