How is the Air Quality Index (AQI) calculated?
Jan 12, 2026| Every day when we open the weather app, we see a number-the Air Quality Index (AQI). It acts as an 'air health report,' telling us whether the air today is suitable for going outside. But do you know how this number is calculated?
The Air Quality Index (AQI) is a comprehensive evaluation of six pollutants: PM2.5, PM10, ozone (O₃), carbon monoxide (CO), sulfur dioxide (SO₂), and nitrogen dioxide (NO₂). Each pollutant has its own sub-index, and the AQI is determined by taking the maximum value among them as the basis for the day's air quality classification.
Monitoring calculation and numerical division
Automatic monitoring stations are distributed throughout the city, collecting air samples in real time. The data is transmitted via the network to the platform, where the system automatically calculates the hourly Air Quality Index (AQI) and updates it on the public platform.
-0-50: Excellent
-51-100: Good
-101-150: Light pollution
-151-200: Moderate pollution
-201-300: Heavy pollution
-300: Severe pollution
When AQI> 100, sensitive populations should reduce outdoor activities; ozone pollution peaks are often in the summer afternoon, and it is recommended to travel during off-peak hours; when PM2.5 pollution is severe, professional protective masks should be worn when going outdoors.
The significance of data
Air Quality Index (AQI) is more than just a number-it reflects a city's energy mix, traffic conditions, and industrial distribution. A drop in AQI marks the success of the Blue Sky Protection Campaign, while a rise signals a natural warning.
Next time you check air quality, pay close attention to specific pollutant data to identify the actual factors affecting your health. After all, clean air requires our collective efforts to protect.