The Air Quality Limit Values Regulations (Northern Ireland) 2002

Classification of zones

5.—(1) The Department shall classify each zone in relation to each of the relevant pollutants according to whether ambient air quality in that zone for that pollutant is required to be assessed by—

(a) measurements;

(b) a combination of measurements and modelling techniques; or

(c) by the sole use of modelling or objective estimation techniques.

(2) Measurements must be used to assess ambient air quality in relation to a relevant pollutant in a zone if—

(a) the zone is an agglomeration;

(b) the levels of that pollutant in the zone are between the relevant limit values and upper assessment thresholds; or

(c) the levels of that pollutant in the zone exceed the limit values for that pollutant.

(3) A combination of measurements and modelling techniques may be used to assess ambient air quality in any zone in relation to a relevant pollutant where the levels of the pollutant over a representative period are below the relevant upper assessment thresholds.

(4) Where the levels of a relevant pollutant in any zone are below the relevant lower assessment thresholds, the sole use of modelling or objective estimation techniques for assessing levels of that pollutant is permissible unless—

(a) the zone is an agglomeration; and

(b) the pollutant being assessed is sulphur dioxide or nitrogen dioxide.

(5) The upper and lower assessment thresholds for the relevant pollutants are determined in accordance with Schedule 2.

(6) Where a zone is classified in relation to a pollutant under paragraph (1)(a), modelling techniques may be used for supplementing the measurements taken in order to provide an adequate level of information on ambient air quality in relation to a relevant pollutant in a zone.

(7) The classification of zones required by paragraph (1) shall include any zones which may be classified by the Department as exceeding limit values for—

(a) sulphur dioxide owing to concentrations of sulphur dioxide in ambient air due to natural sources;

(b) PM₁₀ owing to concentrations of PM₁₀ in ambient air due to—

(i) natural events which result in concentrations significantly in excess of normal background levels from natural sources; or

(ii) the resuspension of particulates following the winter sanding of roads.