Wildfire smoke & air quality

Reading the scale

Category	AQI	What it means
Good	0–50	No precautions needed.
Moderate	51–100	Unusually sensitive people may notice symptoms.
Unhealthy for sensitive groups	101–150	People with asthma, heart or lung conditions, older adults and children should limit prolonged exertion outdoors.
Unhealthy	151–200	Everyone may begin to feel effects. Limit outdoor exertion.
Very unhealthy	201–300	Stay indoors where possible; run filtration if you have it.
Hazardous	301+	Avoid outdoor activity entirely.

Why the smoke is not where the fire is

Wildfire smoke rises into the free atmosphere and is carried by winds aloft, which frequently run in a different direction from surface wind. Plumes routinely cross several states, and smoke from Canadian fires regularly degrades air across the upper Midwest and Northeast with no fire burning anywhere near.

The health concern is fine particulate matter, PM2.5, small enough to reach deep into the lungs. It is the reason air can be hazardous under a sky that only looks slightly hazy.

What actually helps indoors

Close windows and run recirculation rather than fresh-air intake. A HEPA purifier sized for the room makes a measurable difference; a box fan with a furnace filter taped to it is the cheap version and works better than nothing. Avoid adding particulates indoors — candles, frying, vacuuming without a HEPA bag.

If you need to be outside in heavy smoke, a fitted N95 or better filters PM2.5. Cloth and surgical masks do not.

Air quality data from AirNow, the EPA's monitoring network, refreshed hourly. Contours are interpolated between monitoring stations, so conditions between stations are estimated rather than measured. General information only, not medical advice — if smoke is affecting your breathing, contact a clinician.