The zones are used as reporting units of the air quality in Belgium. These zones are defined based on Article 3 of the 2004/107/EC Directive and Article 4 of the 2008/50/EC Directive. A zones shall mean a part of the territory of a Member State, as delimited by that Member State for the purposes of air quality assessment and management (source: 2008/50/EC).2008/50/EC Article 4: Establishment of zones and agglomerations: Member States shall establish zones and agglomerations throughout their territory. Air quality assessment and air quality management shall be carried out in all zones and agglomerations.

The air quality measurements are interpolated on a 4x4 km² grid using Corine Land Cover.

The air quality monitoring networks in Belgium are used for the assessment of air quality under the air quality directives (2008/50/EC & 2004/107/EC).