FAQ
What is PM2.5?
PM2.5 refers to fine particulate matter smaller than 2.5 micrometers. It poses the greatest health risk as it penetrates deep into lungs and enters the bloodstream.
Where does the data come from?
Current values come from the Open-Meteo Air Quality API, which publishes hourly pollutant concentrations modelled by the Copernicus Atmosphere Monitoring Service (CAMS) for each city.
How often is data updated?
The underlying model data is hourly. Our cache refreshes every 15 minutes.
What is a safe PM2.5 level?
WHO recommends annual mean below 5 µg/m³. Levels above 35 µg/m³ are unhealthy for sensitive groups. Above 150 µg/m³ is unhealthy for everyone.
How is AQI calculated?
The US AQI converts pollutant concentrations into a 0–500 scale. We use EPA breakpoints for PM2.5: 0–50 Good, 51–100 Moderate, 101–150 Unhealthy for Sensitive Groups, 151–200 Unhealthy, 201–300 Very Unhealthy, 301+ Hazardous.