AQI Guide
Understanding the Air Quality Index and what it means for your outdoor activities.
What is AQI?
The Air Quality Index (AQI) is used for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be a concern. The AQI focuses on health effects you may experience within a few hours or days after breathing polluted air.
AQI Levels
Good
Air quality is satisfactory. Air pollution poses little or no risk.
Great day to be active outside!
Moderate
Air quality is acceptable. May be a risk for some people who are particularly sensitive to air pollution.
People particularly sensitive to air pollution should consider reducing prolonged outdoor exertion.
Unhealthy for Sensitive Groups
Members of sensitive groups may experience health effects. General public is less likely to be affected.
People with respiratory or heart conditions, the elderly and children should limit prolonged outdoor exertion.
Unhealthy
Everyone may begin to experience health effects. Sensitive groups may experience more serious effects.
Everyone should limit prolonged outdoor exertion.
Very Unhealthy
Health alert: everyone may experience more serious health effects.
Everyone should avoid prolonged outdoor exertion.
Hazardous
Health warnings of emergency conditions. The entire population is more likely to be affected.
Everyone should avoid all outdoor exertion.
Frequently Asked Questions
What is a good AQI for outdoor activities?
An AQI of 0-50 is considered good and safe for all outdoor activities. At 51-100 (Moderate), most people can continue normal activities, but particularly sensitive individuals may want to reduce prolonged or heavy exertion.
How often is AQI data updated?
Air quality data providers typically update their measurements hourly. The data you see reflects the most recent readings available from government agencies and established air quality providers.
What pollutants does AQI measure?
The AQI is calculated from six major pollutants: ground-level ozone (O3), particulate matter (PM2.5 and PM10), carbon monoxide (CO), sulfur dioxide (SO2), and nitrogen dioxide (NO2). The overall AQI is determined by the pollutant with the highest reading.
Why might AQI vary within a city?
Air quality can vary significantly over short distances due to local sources like traffic, industrial facilities, or topography. Valleys may trap pollution, areas near highways have higher pollution, and green spaces often have better air quality.