Air Quality Indexes


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On Snap4CIty multiple Air Quality Indexes are estimated and available.

See for scenarious:

Air Pollutant Emission viewer



EAQI: From European Air Quality Index

Enfuser Air Quality Index

Air quality index is used to describe the air quality in simple terms and an easy-to-understand color scale. It is based on measured air quality data and gives an overall characterization of the actual air quality. Finnish air quality index is a hourly index which describes the air quality today, based on hourly values and updated every hour.

Color Air quality Health impacts Other long term impacts
good no known impacts mild environmental impacts
satisfactory very unlikely mild environmental impacts
fair unlikely clear impacts in vegetation and materials
poor sensitive individuals may experience adverse effects clear impacts in vegetation and materials
very poor sensitive population may experience adverse effects clear impacts in vegetation and materials

The index takes into account the concentrations of sulphur dioxide (SO2), nitrogen dioxide (NO2), respirable particles (PM10), fine particles (PM2.5), ozone (O3) carbon monoxide (CO), and the total reduced sulphur compounds (TRS). The measured concentrations are compared with the current air quality guidelines.

Sub-index definitions

A sub-index is assigned for each of the measured compounds and the highest sub-index determines the overall air quality index at the station.

Index values of the different compounds (sub-indexes), concentration micrograms per cubic meter air (µg/m3)
Index classification SO2 NO2 PM10 PM2.5 O3 CO TRS
good below 20 below 40 below 20 below 10 below 60 below 4000 below 5
satisfactory 20-80 40-70 20-50 10-25 60-100 4000-8000 5-10
fair 80-250 70-150 50-100 25-50 100-140 8000-20000 10-20
poor 250-350 150-200 100-200 50-75 140-180 20000-30000 20-50
very poor above 350 above 200 above 200 above 75 above 180 above 30000 above 50

The air quality index in use in Finland is developed and maintained by the Helsinki Region Environmental Services Authority HSYand the National Institute for Health and Welfare THL.

CAQI: From Wikipedia:

As of 2012, the EU-supported project CiteairII argued that the CAQI had been evaluated on a "large set" of data, and described the CAQI's motivation and definition. CiteairII stated that having an air quality index that would be easy to present to the general public was a major motivation, leaving aside the more complex question of a health-based index, which would require, for example, effects of combined levels of different pollutants. The main aim of the CAQI was to have an index that would encourage wide comparison across the EU, without replacing local indices. CiteairII stated that the "main goal of the CAQI is not to warn people for possible adverse health effects of poor air quality but to attract their attention to urban air pollution and its main source (traffic) and help them decrease their exposure."[34]

The CAQI is a number on a scale from 1 to 100, where a low value means good air quality and a high value means bad air quality. The index is defined in both hourly and daily versions, and separately near roads (a "roadside" or "traffic" index) or away from roads (a "background" index). As of 2012, the CAQI had two mandatory components for the roadside index, NO2 and PM10, and three mandatory components for the background index, NO2, PM10 and O3. It also included optional pollutants PM2.5, CO and SO2. A "sub-index" is calculated for each of the mandatory (and optional if available) components. The CAQI is defined as the sub-index that represents the worst quality among those components.[34]

Some of the key pollutant densities in μg/m3 for the hourly background index, the corresponding sub-indices, and five CAQI ranges and verbal descriptions are as follows.[34]

Frequently updated CAQI values and maps are shown on the and other websites.[33] A separate Year Average Common Air Quality Index (YACAQI) is also defined, in which different pollutant sub-indices are separately normalised to a value typically near unity. For example, the yearly averages of NO2, PM10 and PM2.5 are divided by 40 μg/m^3, 40 μg/m^3 and 20 μg/m^3, respectively. The overall background or traffic YACAQI for a city is the arithmetic mean of a defined subset of these sub-indices.[34]

Helsinki Air Quality Index

It is an estimation of the Air Quality Index adopted in the Helsinki area and provided by FMI sensors in a scale from 1 to 5. Its meaning and mechanisms to its estimation seem to be not available, probably should be similar to those adoptred by Enfuser as described above.

Air quality index from Copernicus The regional air quality (RAQ) production of the Copernicus Atmosphere Monitoring Service (CAMS) is based on partner state-of-the-art numerical air quality models developed in Europe : CHIMERE from INERIS (France), EMEP from MET Norway (Norway), EURAD-IM from University of Cologne (Germany), LOTOS-EUROS from KNMI and TNO (Netherlands), MATCH from SMHI (Sweden), MOCAGE from METEO-FRANCE (France) and SILAM from FMI (Finland). Common to all models, the meteorological parameters settings (coming from the ECMWF global weather operating sytem), the boundary conditions for chemical species (coming fron the CAMS IFS-MOZART global production), the emissions coming from CAMS emission (for anthropic emissions over Europe and for biomass burning).

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