In the air quality directive (2008/EC/50), the EU has set a critical level for nitrogen oxides (NOx) for the protection of vegetation within the zones designated by member states: the NOx annual mean value may not exceed 30 micrograms per cubic metre (µg/m3).
EEA standard re-use policy: unless otherwise indicated, re-use of content on the EEA website for commercial or non-commercial purposes is permitted free of charge, provided that the source is acknowledged (http://www.eea.europa.eu/legal/copyright). Copyright holder: European Environment Agency (EEA).
– it doesn't need to be set higher than 60 ºC. The same goes for the boiler of your central heating. Remember, 70 % of the energy used by households in the EU is spent on heating homes and another 14 % – on heating water.
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