AQI categories at a glance

Quick reference

References describe the U.S. Air Quality Index as the standard public-communication tool for outdoor pollutant concentrations during smoke events. The categories below summarize the U.S. EPA AirNow framework, with health-protective recommendations referenced from EPA, CDC, and California Air Resources Board guidance. The numeric thresholds are PM2.5-driven during wildfire smoke events; ozone and other pollutants use parallel frameworks but are rarely the dominant variable during smoke. References describe sensitive groups as including children, older adults, people with respiratory or cardiovascular disease, pregnant individuals, and outdoor workers.