Titre European Citeair index : Common Air Quality Index (or CAQI)

  • Citeair
    Two air quality indices (background and traffic) for near real time information in European cities.

European Citeair index provides near real time air quality data for each city  for the background (representing the general situation of the given agglomeration) and for the traffic (being representative of city streets with a lot of traffic)


The Citeair index has been developed during the Citeair European project (Citeair – Common information to European air, co-funded by the European Union's INTERREG IIIC and IVC Programmes). This index has been launched in 2006 to the general public to provide:

  • Simple and take into account the traffic pollution.
  • To compare the current air quality across Europe.
  • Suitable to measurement methods of each monitoring network.

This index is currently used by more than a hundred of European cities and is calculated every hour based on monitoring stations.

Citeair Internet site home page

Citeair home page: www.airqualitynow.eu

Calculation of the index

Citeair index scale

In the Ile-de-France agglomeration, it is calculated for Paris city. The Background index representing the general situation is based on urban background monitoring sites. The Roadside index, being representative of city streets with a lot of traffic, is based on roadside monitoring stations. These hourly indices have 5 levels using a scale from 0 (very low) to > 100 (very high).

Considered pollutants:

Indice trafic Indice de fond
  • Mandatory pollutant: Nitrogen dioxide and particulate matter (PM10)

  • Auxiliary pollutant: Carbon monoxide and particulate matter (PM2.5)

  • Mandatory pollutant: Nitrogen dioxide, particulate matter (PM10) and ozone

  • Auxiliary pollutant: Sulfur dioxide, carbon monoxide and Particulate matter (PM2.5) (since 2011)
Display Common air quality index calculation grid.


The CITEAIR index is broadcasted in real time on www.airqualitynow.eu and on news websites (Actu Environnement, Journal de l'environnement ...) and on the hot air balloon Air de Paris (Parc André Citroën) .