Chapter 3
Air Quality Index
One number from 0 to 100 for how clean the air is, where 100 is best. It appears on the sensor page, in the sensor and station lists and in the widgets, for every sensor that measures at least one air pollutant.
01Bands
What the score means
| Score | Band |
|---|---|
| 90–100 | Excellent |
| 75–89 | Good |
| 55–74 | Moderate |
| 35–54 | Poor |
| 15–34 | Very poor |
| 0–14 | Hazardous |
02Calculation
How the score is calculated
- 1Each pollutant gets its own scoreBased on published guidelines (WHO 2021, European Air Quality Index, German UBA indoor values). A value right at the guideline scores about 80.
- 2Related pollutants form one groupPM1, PM2.5, PM4, PM10 and particle counts are one group. A group counts with its worst member.
- 3Groups are combined by importanceA weighted average of the groups. It can be at most 20 points better than the worst group, so good values cannot hide one bad pollutant.
| Group | Weight |
|---|---|
| CO₂ | 3 |
| Particulate matter | 2.5 |
| NO₂, CO | 2 each |
| VOC, ozone, formaldehyde | 1.5 each |
| SO₂, radon | 1 each |
| Humidity | 0.75, indoors only |
03Details
Good to know
Always current
Uses the latest value of each measurement, up to 3 hours old, and is recalculated every time you look.
Humidity alone is not enough
A sensor with only temperature and humidity gets no score. Humidity only adds to the score of indoor sensors.
What limits it
The breakdown shows the two most important groups and one line for the rest, with the pollutant that pulls the score down first.
Stations
A station shows the score of its worst sensor, also on its public station page.