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🍃 Air quality
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Detecting your location…
How clean or polluted the air is right now — based on particulates and gases that affect breathing and health.
Air Quality Index (AQI) values translate the concentrations of several harmful pollutants into a single, easy-to-read number that reflects how clean or polluted the air is and what it means for your health. This page uses the European AQI, which is calculated from fine particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide and sulphur dioxide. The pollutant in the worst category at any moment usually determines the overall index.
Particulate matter is the most health-relevant pollutant. PM2.5 (particles under 2.5 microns) is small enough to reach deep into the lungs and enter the bloodstream; PM10 includes coarser dust and pollen. Ground-level ozone forms when sunlight reacts with pollutants from traffic and industry, and irritates the airways. Nitrogen dioxide comes mainly from vehicle engines, and sulphur dioxide from burning fossil fuels containing sulphur.
Major sources include road traffic, power generation, industry, domestic heating and agriculture. Natural events contribute too: wildfires release enormous amounts of PM2.5, dust storms raise PM10, and vegetation emits compounds that help form ozone. Because pollutants are carried by the wind, poor air quality can travel hundreds of kilometres from its source.
Weather controls how pollution disperses. Wind and rain clear the air — rain literally washes particles out. Calm, stable conditions let pollutants accumulate. A temperature inversion, where a layer of warm air sits over cooler air near the ground, acts like a lid and traps pollution close to the surface, which is why some of the worst smog episodes happen on still, sunny winter days or hot summer afternoons.
Reference monitoring stations draw air through instruments that measure each pollutant continuously — for example, particles are measured by how they scatter light or by their mass on a filter. These ground measurements are combined with satellite data and atmospheric chemistry models to estimate air quality everywhere, including the values shown on this page.
Fine particulate matter, PM2.5, is generally considered the most harmful to health because the particles are small enough to penetrate deep into the lungs and pass into the bloodstream, affecting the heart as well as the lungs.
Heavy exercise makes you breathe in more air, and therefore more pollution. On poor or very poor days it is better to exercise indoors or reduce intensity, especially if you are in a sensitive group.
Cold, still weather and temperature inversions trap pollution near the ground, and more heating fuel is burned. These conditions can cause pollution to build up over several days.
Only when outdoor air is cleaner than indoor air. On high-pollution or wildfire-smoke days, keeping windows closed and using a HEPA purifier is usually better.