The air quality index

How good is the air? Our air quality index shows you. It's based on hourly average measurements of ozone (O₃), nitrogen dioxide (NO₂), particulate matter (PM₁₀ and PM_2.5), and sulfur dioxide (SO₂). Using the most recent hourly data from a station, pollutant concentrations are classified into five index categories from "very good" to "very poor" using threshold values.

AQI class
PM₁₀^*
PM_2,5^*
O₃^*
NO₂^*
SO₂^*

very poor
over 90
over 50
over 240
over 100
over 100

poor
55-90
31-50
145-240
61-100
61-100

moderate
28-54
16-30
73-144
31-60
31-60

good
10-27
6-15
24-72
11-30
11-30

very good
0-9
0-5
0-24
0-10
0-10

^* Hourly means in µg/m³

These threshold values were derived based on current health studies and taking into account the recommendations of the World Health Organization (WHO). The pollutant with the worst rating determines the LQI classification and thus the index class and color. The circle symbol at each station indicates whether all five pollutants are measured, distinguishing between:

"Complete circle": all 5 pollutants are measured at the station. An assessment of air quality and resulting health recommendations are fully possible.

"Incomplete circle": fewer than five pollutant measurements are available; i.e., at least one pollutant was not measured. A comprehensive assessment of air quality and resulting health recommendations may not be possible. Nevertheless, the available results provide an indication of current air quality.

It is not always necessary to measure all five pollutants at the monitoring stations. This is not unusual. If there is a low initial level of one pollutant, continuous measurement at that station is not required.

The following table shows the behavioral tips of the German Environment Agency. Because air quality is not always the sole cause of health problems, medical advice should generally be sought in the case of persistent or recurring symptoms, regardless of air quality.

Index
Risk
Health advise and recommendations:

General hints
Our recommendation for the general public
Our recommendation for particularly sensitive groups¹

very poor
People with lung and cardiovascular diseases, children, and the elderly may experience health problems. Even healthy people can experience symptoms such as coughing or shortness of breath.
Engage in strenuous outdoor activities at times or in places with better air quality (e.g., less traffic). Reduce your physical activity if you experience symptoms such as coughing or shortness of breath.
Avoid strenuous outdoor activities or shift them to times or places with better air quality (e.g., less traffic). Reduce or stop your physical activity if you experience symptoms such as coughing or shortness of breath. Consult a doctor if symptoms persist.

Poor
Health problems may occur in people with lung and cardiovascular diseases, children and the elderly.
Whenever possible, engage in strenuous physical activities, such as outdoor sports, at times or in locations with better air quality (e.g., less traffic). Reduce your physical activity if you experience symptoms such as coughing or shortness of breath.
Engage in strenuous outdoor activities at times or in places with better air quality (e.g., less traffic). Reduce or stop your physical activity if you experience persistent symptoms such as coughing or shortness of breath, and seek medical advice.

Moderate
People with lung and cardiovascular diseases may experience health problems.
Enjoy your outdoor activities.
If possible, engage in particularly strenuous physical activities, such as outdoor sports, at times or in places with better air quality (e.g., less traffic). Reduce your physical activity if you experience recurring symptoms such as coughing or shortness of breath.

Good
Health problems due to air pollutants are unlikely.
Enjoy your outdoor activities.
Enjoy your outdoor activities.

very good
No health problems are expected due to air pollutants.
Enjoy your outdoor activities.
Enjoy your outdoor activities.

¹ People with pre-existing conditions such as asthma or cardiovascular diseases, children, pregnant women or elderly people

Further background information on the AQI and the derivation of the index classes can be found at
Der Luftqualitätsindex - LQI. Only available in German.