The Air Quality Index provides users with a better understanding of the air quality in the places they live, work or travel. By displaying up-to-date information and real-time measurement data, users can get a simple overview of the air quality in individual cities and municipalities.
The index is based on hourly concentrations of five key pollutants: particulate matter (PM10 and PM2.5), nitrogen dioxide (NO₂), ozone (O₃) and sulphur dioxide (SO₂).
The index indicates the short-term (hourly) state of air quality. It does not reflect the long-term (annual) state of air quality, which can differ significantly from the short-term.
The index is consistent with the European Air Quality Index which started to be applied on 04 July 2025.
The concentration values of the five key pollutants determine the level of the index reflecting the air quality at each monitoring station. The index corresponds to the level of the pollutant that has the highest concentration of the five pollutants according to the following scheme.
The index ranges are complemented by health messages that provide recommendations for both the general population and vulnerable population groups. The latter include adults and children with respiratory problems and adults with heart disease.
