Sulphur dioxide - Daily limit value for the protection of human health

In the air quality directive (2008/EC/50) the EU has set two limit values for sulphur dioxide (SO2) for the protection of human health: the SO2 hourly mean value may not exceed 350 micrograms per cubic metre (µg/m3) more than 24 times in a year and the SO2 daily mean value may not exceed 125 micrograms per cubic metre (µg/m3) more than 3 times in a year.