Air Quality Index (Atmo)

The air quality index is a quantified indicator that makes it possible to give an air quality assessment on a scale of 1 to 10. There are two daily air quality indices, different depending on the size of the agglomeration: • The ATMO index necessarily calculated in agglomerations with more than 100 000 inhabitants; • The “simplified” air quality index (AQI) calculated in agglomerations or zones geographical area with less than 100,000 inhabitants. These indices shall be calculated in accordance with the provisions of Article 3 of the Decree of 22 July 2004 as amended by the Order of 21 December 2011. They are determined from the levels of pollution measured during of the day by the underground stations responsible for monitoring the general pollution of the agglomeration. They do not take into account measuring stations directly related to traffic. They integrate the main ones air pollutants, tracers of urban activities (transport, tertiary, etc.), domestic and industrials: • nitrogen dioxide (NO2); • sulphur dioxide (SO2); • particles (PM10); • ozone (O3).