AQI explained — what 50, 100, 150 actually mean for your lungs

The 6 AQI categories

0–50: Good (green). Air quality is satisfactory; no health concerns.

51–100: Moderate (yellow). Acceptable for most. Unusually sensitive people may experience minor symptoms.

101–150: Unhealthy for Sensitive Groups (orange). People with lung disease, older adults, children, and those with heart disease may experience health effects.

151–200: Unhealthy (red). Everyone may begin to experience effects; sensitive groups may experience more serious effects.

201–300: Very Unhealthy (purple). Health alert; everyone may experience more serious effects.

301+: Hazardous (maroon). Health warnings of emergency conditions; entire population is more likely to be affected.

Which pollutants drive the AQI

PM2.5 (fine particulates): combustion smoke (wildfires, vehicle exhaust, industrial). The most-cited driver during wildfire smoke events. Penetrates deep into lungs.

PM10 (coarse particulates): dust, pollen, ash. Less penetrative but still irritating.

Ozone (O3): formed by sun + NOx + VOCs. Summer afternoons in cities. Worse in heat waves.

NO2, SO2, CO: traffic and industrial. Less common as the dominant AQI driver but matter near busy roads.

When to take precautions

AQI 100+: sensitive groups (asthma, COPD, kids under 5, adults 65+) should reduce prolonged outdoor activity.

AQI 150+: everyone should reduce strenuous outdoor activity. Mask up if going outside (N95 or KN95 — surgical masks don't filter PM2.5).

AQI 200+: stay indoors. Use a HEPA air purifier if you have one. Close windows. Run AC on recirculate.

Wildfire smoke: even short-term exposure to high PM2.5 raises cardiovascular risk. Don't 'tough it out'.

What zipradar shows

We pull from EPA AirNow's nearest monitoring station to your ZIP. Real-time AQI plus the multi-year average for context.

Rural ZIPs may have a station 50+ miles away — we show the distance so you know how representative the reading is.