In order to protect human health and vegetation from the effects of excessive air pollution, the air quality is continuously examined and assessed in accordance with legal regulations. For this purpose, the State Office for Agriculture, Environment and Rural Areas (LLUR) in Schleswig-Holstein operates a network of measuring stations at which air pollutants are measured using different methods. The measurement data from Schleswig-Holstein and a lot of additional information about the measurements are forwarded to the Federal Environment Agency and from there reported to the European Commission together with the data from all federal states. All currently published data are classified as preliminary, as they are first automatically checked for validity for your quick information. Before the final evaluation and assessment of the air quality, a multi-stage test is carried out in accordance with legal requirements. In the CSV files, the 3 o'clock measurement is "missing" on the day of the change from standard time (CET) to summer time (CEST), but there are two 3 o'clock measurements on the day of the change from summer to normal time. The JSON files are not affected by this problem; standard time is used here throughout. Information on the measuring station