The network of measuring stations registered in the ISKO database in 2022. The basis for the air quality assessment is the concentrations measured at the monitoring stations. The measurement network is densest in the areas with the highest concentrations of pollutants, but covers the whole Czech Republic. The backbone network of monitoring stations is the National Air Quality Monitoring Network (NAQMN), operated by the CHMI. It includes both stations with an automated monitoring programme (AIM) and stations with a manual monitoring programme (MIM), from which the samples taken are analysed in the laboratories of the CHMI. In many cases, air pollution at one site is monitored simultaneously by both automatic and manual methods. The national network of concentration monitoring is supplemented by monitoring stations of other organisations, whose measurements are also used in the assessment of air quality.