What is the Air Quality Index (AQI)?

The Air Quality Index (AQI) is a scale from 0 to 500 used to communicate how polluted the air is and what associated health effects might be a concern. Lower values indicate cleaner air.

What is PM2.5 and why is it dangerous?

PM2.5 refers to fine particulate matter smaller than 2.5 micrometres. These tiny particles can penetrate deep into the lungs and bloodstream, causing respiratory and cardiovascular problems.

How often is the air quality data updated?

AQIWatcher refreshes air quality data every 10 minutes using the Open-Meteo Air Quality API, which provides hourly forecast data.

Is AQIWatcher free to use?

Yes, AQIWatcher is completely free. It uses the open-source Open-Meteo API which requires no API key.

Which pollutants does AQIWatcher track?

AQIWatcher tracks PM2.5, PM10, ozone (O3), nitrogen dioxide (NO2), carbon monoxide (CO), and sulphur dioxide (SO2).

How do I compare air quality between two cities?

Use the Compare page at aqiwatcher.app/compare. Search for any two cities and AQIWatcher will display a side-by-side pollutant comparison with AQI scores and health recommendations for both.

Can I get alerts when air quality gets bad?

Yes. On the Dashboard page, go to the Alerts tab to set AQI and PM2.5 thresholds. AQIWatcher will send browser push notifications when those thresholds are exceeded.

Which cities have the best air quality?

Visit the City Rankings page at aqiwatcher.app/rankings to see the 20 cleanest and 20 most polluted cities worldwide based on real-time AQI data.

What does AQI 150 mean?

An AQI of 150 falls in the Unhealthy range. Everyone may begin to experience health effects. Members of sensitive groups may experience more serious health effects. It is advisable to reduce prolonged or heavy outdoor exertion.

How does weather affect air quality?

Weather significantly impacts air quality. Wind disperses pollutants, rain washes particles from the air, temperature inversions trap pollution near the ground, and high temperatures accelerate ozone formation. AQIWatcher provides weather context alongside AQI data.

Is PM2.5 or AQI more important to track?

Both are important but serve different purposes. AQI is a composite health index that is easy to interpret at a glance. PM2.5 is a specific pollutant measurement - the most harmful to human health - that feeds into the AQI calculation. Tracking both gives you the most complete picture.

Can I embed AQIWatcher on my website?

Yes. Visit aqiwatcher.app/widget to generate an embeddable air quality widget for any city. The widget updates automatically with live AQI data and can be customised for size and appearance.

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