Guide
How to check air quality where you are
What the European Air Quality Index measures, the difference between readings and forecasts, and when to change your plans.
Updated 14 November 2026
Air quality can change a lot within a day. Knowing what the index means, and whether you are looking at a measurement or a forecast, helps you decide when to open the windows, exercise outside or keep a child indoors.
What the European Air Quality Index measures
The European Air Quality Index, published by the European Environment Agency, rates air from "good" to "extremely poor" using five pollutants: fine particles (PM2.5), coarser particles (PM10), nitrogen dioxide, ozone and sulphur dioxide. The overall rating is set by the worst of them. PiSpace Air's pollutant guides explain where each one comes from and how it affects health.
Readings and forecasts are different things
A reading comes from a monitoring station and describes the air at that place in the past hour. A forecast comes from a model and describes what the air is expected to be over a wider area. Both are useful: readings tell you what is happening now, forecasts help you plan tomorrow. PiSpace Air labels which one you are looking at and when it was made.
Which pollutant to watch
- Fine particles come from traffic, wood burning and industry. They are the main concern in many European cities in winter.
- Nitrogen dioxide is highest near busy roads during rush hour.
- Ozone builds up on sunny, still summer afternoons, often outside cities.
When to change your plans
For most healthy adults, short periods of moderate air are not a reason to stay inside. People with asthma, heart or lung conditions, older people, pregnant women and children are more sensitive and should take care earlier, especially with outdoor exercise. Follow the advice of your doctor and your national health service, which takes precedence over any website.
Looking at a city before you move
For a move, one day says little. Look at how many days in a typical month the index is poor or worse, and in which season. The European overview is a good starting point, and each city page on this site links to that city's air quality page.
Sites used in this guide
- PiSpace Air: Air quality readings and forecasts, Europe first.