AQI Colors and Numbers

AQI scale for particular matter and ozone levels


The US Environmental Protection Agency developed a common air pollutants scale to communicate pollution levels in a standardized way. This scale is the same for particulate matter and ozone. And AQI reading of 101 indicates a level above the national air quality standard. The higher the rating, the greater the health impact.

Air Quality Index Colors

The AQI is divided into color-coded categories. Each category is labeled by an informative descriptor. Descriptors are intended to convey information to the public about how air quality relates to public health.

AQI Numbers AQI Descriptor AQI Color
0 - 50 Good green
51 - 100 Moderate yellow
101-150 Unhealthy for Sensitive Groups orange
151 - 200 Unhealthy red
201 - 300 Very Unhealthy purple
300 - 500 Hazardous maroon

AQI Observations

Hourly or daily observations are measured and reported to the EPA's AirNow website (our source for the data) by federal, state, local, and tribal air quality agencies. Historical (daily) Air Quality Index values are calculated using an averaging method and real-time AQI values are based on a surrogate calculation.

Learn more by visiting the offical US EPA website