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AirQuality.city is an independent hobby project. Donations help cover hosting, sensors, enclosures, replacement parts and expansion of the local monitoring network.
Pages
Explainers on air quality, how it is measured, and how to read the data.
Air quality in Croatia depends on location, season and weather
Croatia does not have one uniform air-quality level. Traffic, heating, industry, terrain, wind, fires and Saharan dust can change conditions from hour to hour and place to place.
Frequently asked questions about air quality
Short answers to the questions that most often come up around AQI, PM2.5 and PM10, differences between services, fog, sensors and official monitoring stations.
One number is not the whole picture of air quality
AQI is a useful starting point, but better interpretation also needs concentration, timestamp, trend, station location and the pattern at nearby sites.
From sensor to map: how data moves through AirQuality.city
AirQuality.city combines its own SensorBox stations with official monitoring networks. The data is produced differently, so the portal keeps those differences visible rather than hiding them.
The same city can show a different AQI on different services
A different colour or number does not automatically mean that one service is wrong. The difference may come from another station, index, averaging period or pollutant set.
Privacy and Cookies
AirQuality.city processes only the information needed to operate and protect the website, communicate with users and send the newsletter. We do not use analytics or advertising cookies.
Terms of Use
Rules governing the use of AirQuality.city, including the purpose of the portal, data limitations, permitted use of content and liability.
About AirQuality.city
AirQuality.city is an independent hobby project combining local SensorBox measurements with publicly available official data to make air quality easier to follow and understand.
Join the project
AirQuality.city grows through new monitoring locations, technical contributions and people willing to help make local air-quality data more accessible.
Data sources and methodology
Technical documentation covering data sources, SensorBox processing, the PM index, timestamps, official monitoring data and the limitations of AirQuality.city measurements.
AQI turns pollutant concentrations into a simpler air-quality signal
AQI makes air quality easier to scan, but it is not a universal measure. The US and European systems use different thresholds, averaging rules and pollutant sets.
AQI scale and the meaning of each category
AirQuality.city uses the six U.S. EPA AQI categories for PM2.5 and PM10. The number is useful for quick interpretation, but category boundaries are not sudden physical changes in the air.
PM2.5 and PM10: small particles with different sources and risks
PM2.5 and PM10 are not two chemicals but two particle-size fractions. They differ in sources, atmospheric behaviour and how deeply they can penetrate the respiratory system.
NO₂, O₃, SO₂ and CO: gases a PM sensor cannot see
Particulate matter is not the only air-quality concern. Official stations also monitor nitrogen dioxide, ground-level ozone, sulphur dioxide and carbon monoxide, each with different sources and behaviour.
From measurement to display: the AirQuality.city methodology
AirQuality.city combines several data sources, checks freshness and displays concentrations, trends and a PM index while keeping the limitations visible.