O3

Definition

Ozone (O3) is a secondary pollutant formed from a complex series of chemical reactions of primary precursor pollutants, mainly NOx and VOCs, in the presence of solar radiation.

Ozone has a positive effect in the stratosphere, where it forms the so-called ozone layer, as it protects against ultraviolet radiation. However, in the troposphere it becomes a pollutant that acts as a powerful and aggressive oxidising agent.

Predominant sources of emissions

Ozone is a pollutant of concern in outdoor air, as the primary pollutants with which it reacts mainly come from road traffic, but ozone is also generated indoors by the use of electrical appliances such as photocopiers, laser printers, ionising air cleaners or disinfection devices.

Legislation and intervals

According to World Health Organization: The limit value for O3 is 100 μg/m3 for 8 hours average.

According to DIRECTIVE 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe: The limit value for O3 is 120 μg/m3 for 8 hours average.