Understanding air quality
How air quality is measured, and what the numbers mean
Air quality is read through a set of pollutants, indices and weather conditions. We explain how monitoring works and how to place official readings in context across Île-de-France.
Monitoring indices
Reading indices with their context
Monitoring relies on several indicators that track different microscopic elements in the atmosphere. Each index summarises a set of measurements, so a single value rarely tells the whole story.
Weather also shapes what residents breathe. Thermal inversions can trap pollutants near the ground, changing how they disperse across the metropolitan area from one season to the next. Our articles explain these dynamics in detail.
How observatories work
From sampling to interpretation
01
Sampling
Fixed and mobile stations collect air samples at defined locations across the region, using standardised measurement methods.
02
Analysis
Instruments quantify the concentration of selected pollutants, which are then compared with reference thresholds set by public authorities.
03
Interpretation
Experts combine the results with weather data and local context to produce public indices and bulletins that readers can verify at the source.