What does the air quality index (AQI) number mean?

The AQI rolls up ozone, particulates, and a few other pollutants into one number so you don't need a chemistry degree to know if it's a bad-air day. 0-50 is good, 51-100 is fine for most people but worth a second thought if you're sensitive to pollution, and anything past 100 starts affecting healthy people too, not just at-risk groups. We show it for every location for free, full stop — it's a safety number, not a premium feature.