Air Quality
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PM2.5 are fine particles, microscopic soot from vehicles, industry, and wildfire smoke, small enough to reach deep into the lungs and the bloodstream. Usually the main driver of a bad-air day here.
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O₃ is ground-level ozone, formed when sunlight cooks car and factory emissions, so it peaks on hot, sunny afternoons. It inflames the airways and makes breathing harder.
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PM10 are coarse particles like dust, pollen, and mold stirred up by wind, farming, and construction. They irritate the eyes, nose, and throat.
The Air Quality Index (AQI) runs from 0 to 500 — the higher it climbs, the more people are affected and the more serious the effects. Each hour it’s set by whichever pollutant is worst at the time.
- Good0–50
Air quality is satisfactory and poses little or no risk.
- Moderate51–100
Acceptable, though unusually sensitive people may notice minor effects.
- Unhealthy for Sensitive Groups101–150
Children, older adults, and people with heart or lung conditions may feel effects; most others won’t.
- Unhealthy151–200
Everyone may begin to feel effects, and sensitive groups more seriously.
- Very Unhealthy201–300
A health alert — the risk of effects is heightened for everyone.
- Hazardous301–500
Emergency conditions; the entire population is likely to be affected.
Sources: EPA AirNow