Air quality index
Air quality AQI European Air Quality Index
An air quality index turns pollutant concentrations into an understandable rating. The meaning of a number or colour depends on the particular index.
One display for several pollutants
Particles, ozone and other pollutants affect health differently. An air quality index first rates their concentrations separately. The European index covers PM2.5, PM10, nitrogen dioxide, ozone and sulphur dioxide. The poorest available individual rating determines the overall category.
Why not just take an average?
If four pollutants are low and one is high, averaging could hide the problem. The overall index therefore highlights the least favourable result. Check which pollutant is responsible.
Fifty does not always mean the same thing
The European index, Germany’s LQI and the US AQI can use different scales, thresholds and averaging periods. Methods can change too. A number only makes sense with its own legend. It is not a concentration in µg/m³ either.
What the index cannot do
- It describes the assessed pollutants and stated period, not every property of the air.
- An hourly index does not establish compliance with an annual limit.
- An area model value is not a measurement beside a particular road.
Personal decisions also depend on location, exposure duration and sensitivity. Guidance from official monitoring services helps when pollution is elevated.