Six colours. Six numbers. And one band almost everybody misreads.
Start here
100
is the line
Below 100, air quality is satisfactory. Above 100 it is unhealthy — first for certain groups, then for everyone as the number climbs.
Green
0–50
Good
Air quality is satisfactory and air pollution poses little or no risk. Nothing to change.
Yellow
51–100
Moderate
Acceptable — but there may be a risk for people who are unusually sensitive to air pollution.
Orange — the one people misread
101–150
Unhealthy for Sensitive Groups
Most air quality alerts sit here. It sounds like somebody else’s problem. It usually is not.
Who is a sensitive group
Count your household. Most have at least one.
Red
151–200
Unhealthy
Some of the general public may feel effects; sensitive groups more seriously. Everyone should cut back on prolonged outdoor exertion.
Purple
201–300
Very Unhealthy
A health alert: the risk of effects is increased for everyone. Avoid outdoor exertion, keep windows shut.
Maroon
301+
Hazardous
A health warning of emergency conditions. Everyone is more likely to be affected. Stay indoors.
One thing worth knowing
Breathing harder and deeper pulls more pollutant into your lungs. A red-band run puts more in than a red-band walk.
Scale and wording per the EPA’s AirNow. General information, not medical advice.