| Grid computing the index of air quality 
 
 
 
| Contamination | Index | Major Pollutants | Other Pollutants |  | NO2 | O3 | PM10 | CO | SO2 |  | Very high | > 100 | > 400 | > 240 | > 180 | > 20000 | > 500 |  | High | 100 | 400 | 240 | 180 | 20000 | 500 |  | 76 | 201 | 181 | 91 | 10001 | 301 |  | Average | 75 | 200 | 180 | 90 | 10000 | 300 |  | 51 | 101 | 121 | 51 | 7501 | 101 |  | Low | 50 | 100 | 120 | 50 | 7500 | 100 |  | 26 | 51 | 61 | 26 | 5001 | 51 |  | Very Low | 25 | 50 | 60 | 25 | 5000 | 50 |  | 0 | 0 | 0 | 0 | 0 | 0 |  
The air quality is rated on a 5-point scale from 0 (low pollution) over 100 (very high pollution). It is based on three main pollutants: PM 10 (particulate matter), NO2 (nitrogen dioxide), O3(ozone) and may consider two additional pollutants that is to say, CO (Carbon monoxide  and SO2 (sulfur dioxide) to the cities for which data are available.NO2 , O3 , SO2 : hourly value / maximum hourly value in μg/m3PM 10 : hourly value / maximum hourly value or average daily adjusted μg/m3CO: moving average 8 hours / moving average maximum of 8 hours in μg/m3
 
 Calculating air quality is based on a review of various local measures air quality and reflects . to as much as possible the alert thresholds or daily limits In order to make comparable cities and to overcome the nature of the monitoring network, two indices are defined.
 
 
Index background (global), representing the general situation of the agglomeration (based on urban background monitoring sites)Index near traffic, representing busy roads (based on monitoring stations along the route) |