Air quality index
With the help of the air quality index, the concentrations of different pollutants are divided into five categories, from good to very poor. The air quality index is a simplified way of illustrating real-time (hour by hour) air quality.
The index is based on health impacts, limit values and guidelines for air quality. When air quality is poor, health impacts are possible on sensitive individuals.
Sub-indices are calculated for sulphur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), ozone (O3), fine particles (PM2,5) and thoracic particles (PM10). The highest detected value determines the air quality index. The index rating is 100 when anyone of the concentrations meets the guideline or limit value level.
Table: Air quality classes and the connection between health impacts
| Class |
|
Health impacts |
Other long-term impacts |
| Very poor |
|
Adverse effects possible on sensitive subpopulation |
Clear impacts on vegetation, material impacts |
| Poor |
|
Adverse effects possible on sensitive individuals |
Clear impacts on vegetation, material impacts |
| Fair |
|
Unlikely effects |
Clear impacts on vegetation, material impacts |
| Satisfactory |
|
Very unlikely effects |
Mild environmental impacts |
| Good |
|
No health effects |
Mild environmental impacts |
Table. The concentrations behind the classes of the finnish air quality index since april 2007.
Air quality
(value) |
CO |
NO2 |
SO2 |
O3 |
PM10 |
PM2.5 |
TRS |
Good
(<50) |
<4 |
<40 |
<20 |
<60 |
<20 |
<10 |
<5 |
Satisfactory
(50-75) |
8 |
70 |
80 |
100 |
50 |
25 |
10 |
Fair
(75-100) |
20 |
150 |
250 |
140 |
100 |
50 |
20 |
Poor
(100-150) |
30 |
200 |
350 |
180 |
200 |
75 |
50 |
Very poor
(>150) |
>30 |
>200 |
>350 |
>180 |
>200 |
>75 |
>50 |
Unit per hour, mikrograms per cubic meter (µg/m
3), carbon monoxide CO (mg/m
3).
For an example: When the number of air quality index rises above 51, the air quality turns from good to satisfactory.