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.

ColorAir qualityHealth impactsOther long term impacts
goodno known impactsmild environmental impacts
satisfactoryvery unlikelymild environmental impacts
fairunlikelyclear impacts in vegetation and materials
poorsensitive individuals may experience adverse effectsclear impacts in vegetation and materials
very poorsensitive population may experience adverse effectsclear 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 classificationSO2NO2PM10PM2.5O3COTRS
goodbelow 20below 40below 20below 10below 60below 4000below 5
satisfactory20-8040-7020-5010-2560-1004000-80005-10
fair80-25070-15050-10025-50100-1408000-2000010-20
poor250-350150-200100-20050-75140-18020000-3000020-50
very poorabove 350above 200above 200above 75above 180above 30000above 50

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