Air Quality – Preliminary Data

In accordance with Annex 2 of Decree 106/2025 Coll., which implements certain provisions of the Act on the Public Hydrometeorological Service, the Czech Hydrometeorological Institute (CHMI) has made operational (unverified) primary and aggregated data available for outdoor air pollutants (pollutant concentrations from automatic monitoring stations, provided in the scope and temporal aggregations specified by Act No. 201/2012 Coll., on Air Protection). The data include key pollutants with ambient air limit values under 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), suspended particles PM₁₀, suspended particles PM₂.₅, and sulfur dioxide (SO₂). The data are based on measurements from CHMI-owned stations since 1969. Primary data are provided in measurement intervals of 30 minutes, 1 hour, or 24 hours, depending on the type of measurement. Aggregated data are calculated from the aforementioned primary data and include the following: daily averages, monthly averages, annual averages, and the number of exceedances of ambient air limit values. Preliminary data include air quality information that is older than one hour. Verified data can be found in the dataset *Air Quality Measurements – Verified Data*, in accordance with the data verification process. Verification is carried out once a year, no later than July 1st (YYYY-1).