Air quality guides

Air quality guides

Understand PM2.5, PM10, AQI, data sources and ranking methods. Practical explanations for air quality charts.

PM2.5 vs PM10 - understanding particles in the air

What PM2.5 and PM10 mean, how to read µg/m³ and how hourly, daily and annual concentrations differ. Practical examples for air quality tables.

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How to read AQI and air quality categories

AQI versus µg/m³: understand the six EEA categories, pollutant thresholds and the difference between an hourly category and a daily average.

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Modelled air quality vs station measurements

How CAMS model data differs from monitoring stations, where Pollution Alert gets its data and why dates, location and archive sources matter.

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How our air pollution ranking is calculated

How cities enter the PM2.5 ranking: shared dates, model sources, sorting, ties and limitations. Understand what the air pollution ranking can tell you.

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PM2.5 · PM10 · NO₂ · O₃

Understanding air quality and pollution data

What do PM2.5 and PM10 mean?

PM2.5 and PM10 are fractions of airborne particulate matter. PM2.5 covers fine particles up to 2.5 micrometres in diameter, while PM10 covers particles up to 10 micrometres. Concentrations in µg/m³ tell you how many micrograms of particles are present in a cubic metre of air. Compare values over the same time period.

Where does the air pollution data come from?

The latest concentrations come from the CAMS atmospheric model via Open-Meteo for each city’s coordinates. Values describe a model area, so conditions on individual streets may differ. Historical monitoring station data is shown separately where available.

How does PM2.5 concentration differ from AQI?

PM2.5 is the concentration of one particle fraction, expressed in µg/m³. AQI is an index calculated using a particular scale and thresholds. The pollutant cards show concentrations. Our city ranking compares PM2.5; PM10, ozone, nitrogen dioxide and other available gases add to the picture of air quality.

Which dates do the values and charts cover?

Each current value has a data date and time. Current concentration cards show the latest available hour, daily charts summarise individual days, and monthly records let you compare longer periods. These values represent different time intervals.

How can I check pollution in my city?

Search for your city and open its air quality page. Start with PM2.5 and PM10, then check the other available pollutants and the data timestamp. Charts and tables help you compare concentrations over time. Weather and historical climate information complement the pollution data.