Understanding Air Quality Alerts
What AQI (Air Quality Index) Means
The Air Quality Index (AQI) is a standardized scale for measuring outdoor air quality developed by the EPA. Like the UV Index, higher AQI numbers indicate worse conditions. The scale runs from 0 to 500+: 0-50 (Good — green): Air quality is satisfactory, outdoor activities are fine. 51-100 (Moderate — yellow): Air quality is acceptable, sensitive groups should be cautious. 101-150 (Unhealthy for Sensitive Groups — orange): Children, elderly, and people with respiratory conditions should limit outdoor activity. 151-200 (Unhealthy — red): Everyone may begin to experience health effects, outdoor activities should be limited. 201-300 (Very Unhealthy — purple): Health warnings, everyone should avoid prolonged outdoor activity. 301+ (Hazardous — maroon): Health emergency, everyone should avoid all outdoor activity.
Try it in the app:
In SunUp, look below the UV Index display for the AQI reading. It shows the current number and a color-coded label.
Pro tip:
AQI measures a combination of pollutants including ground-level ozone, particulate matter (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. SunUp primarily focuses on PM2.5 and ozone — the pollutants most relevant to outdoor exercise.