Official AQI Index Thresholds & Health Categories
The Air Quality Index (AQI) converts complex atmospheric chemical measurements into an accessible scale from 0 to 500, established by global environmental protection agencies.
| AQI Range | Status | Color Code | Health Recommendations |
|---|---|---|---|
| 0 – 50 | Good | Green | Air quality is satisfactory. Ideal conditions for outdoor activities and exercise. |
| 51 – 100 | Moderate | Yellow | Acceptable air quality. Extremely sensitive individuals may experience mild respiratory symptoms. |
| 101 – 150 | Unhealthy for Sensitive | Orange | Members of sensitive groups (children, seniors, asthmatics) should limit prolonged outdoor exertion. |
| 151 – 200 | Unhealthy | Red | General public may begin to notice adverse symptoms. Sensitive groups should avoid outdoor activity. |
| 201 – 300 | Very Unhealthy | Purple | Health alert: Serious risk of respiratory distress for everyone. Keep indoor windows sealed. |
| 301 – 500 | Hazardous | Maroon | Emergency warning conditions. The entire population is likely to be severely affected. |
Key Atmospheric Pollutants Explained
Fine Particulate Matter (PM2.5)
Microscopic aerosol particles with diameters under 2.5 microns, originating from vehicle combustion, industrial emissions, and wildfires. When inhaled, PM2.5 passes through alveolar tissues into blood circulation.
Coarse Dust Particles (PM10)
Inhalable particles smaller than 10 microns, commonly produced by mechanical grinding, dust storms, road dust, and construction activities. They irritate upper respiratory airways and eyes.
Ground-Level Ozone (O₃)
Formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of intense solar ultraviolet radiation. Ozone is a potent pulmonary irritant.