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AQI thresholds — what 'unhealthy for sensitive groups' actually means for you
AirNow flashes a number. Whether you should change your day depends on whether you're in a 'sensitive group' — and that label is broader than most people assume.
Published 2026-04-25 · Last reviewed 2026-04-25 · methodology
The six AQI bands
0–50 (green): Good. No precautions needed.
51–100 (yellow): Moderate. Unusually sensitive people should consider reducing prolonged outdoor exertion.
101–150 (orange): Unhealthy for Sensitive Groups. Specific populations should reduce exertion (see below).
151–200 (red): Unhealthy. Everyone may experience effects; sensitive groups should reduce exertion further.
201–300 (purple): Very Unhealthy. Health alert; most people should avoid all outdoor exertion.
301+ (maroon): Hazardous. Emergency conditions. Stay indoors with windows closed, run filtration if possible.
Who counts as 'sensitive' (orange band)
Anyone with asthma, COPD, or other lung disease.
People with heart disease.
Pregnant people.
Children under 18 (developing lungs).
Adults 65+.
Outdoor workers + athletes during prolonged exertion.
That's roughly 40% of the US population on any given day. 'Sensitive' is not a small carve-out.
Pollutant-specific subbands
AirNow rolls up five pollutants (O3, PM2.5, PM10, CO, NO2) into one composite — but the dominant pollutant matters.
PM2.5 (fine smoke particles): wildfire seasons + diesel-heavy corridors.
Ozone: peaks 12–6pm in summer; sensitive to heat + traffic. Ground-level only; stratospheric is fine.
When dominant pollutant matters, AirNow's daily forecast page surfaces it.
Action thresholds
Sensitive group + AQI ≥101: shorten outdoor activity to <30 min, switch to indoor exercise.
Anyone + AQI ≥151: cancel non-essential outdoor exercise; run HEPA filtration indoors.
Anyone + AQI ≥201: stay indoors, mask N95 if you must go out, watch for symptoms.
AQI ≥301: emergency. Watch for evacuation orders.
What zipradar shows
Per-ZIP rolling 30-day AQI summary from EPA AirNow API. We show daily peaks + seasonal patterns (e.g., wildfire-smoke months in CA/OR/WA).
Real-time current AQI is best read at airnow.gov directly — we link out for now.
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