Zones and agglomerations layer for air quality assessment and management in the Czech Republic. The zones and agglomerations are defined on the basis of the legislative specifications of the EU Directive 2008/50/EC and Act No. 201/2012 Coll., on Air Protection. A zone is an area defined by the Ministry of the Environment for the purpose of monitoring and managing air quality; an agglomeration shall mean a zone that is a conurbation with a population in excess of 250 000 inhabitants.

In accordance with Act 123/1998 Coll. on free access to environmental information, as amended, the CHMI has provided verified primary and aggregated data on outdoor air pollutants. These are the main pollutants with limit values according to current legislation: arsenic (As), benzene, benzo[a]pyrene, cadmium (Cd), carbon monoxide (CO), nickel (Ni), nitrogen dioxide (NO2), nitrogen oxides (NOX), ground-level ozone (O3), lead (Pb), particulate matter (PM10), particulate matter (PM2.5), sulphur dioxide (SO2). The data are based on measurements at stations owned by the CHMI for the period 1969-2022. The primary data are presented in measurement intervals of 30 min, 1 h or 24 h, depending on the type of measurement. Aggregated data are calculated from the above primary data. These data are: daily mean values, monthly mean values, annual mean values and the number of exceedances of the limit values for the protection of human health. Verified data for subsequent calendar years from 2020 will always be available by 1 July of the following year.