The color-coded air quality scale is a quick way to show whether outdoor air is healthy to breathe. The scale runs from green for good air quality to maroon for hazardous conditions, with health risks generally increasing as the Air Quality Index rises.
What are the major pollutants that affect the scale?
According to the EPA’s AirNow site:
EPA establishes an AQI for five major air pollutants regulated by the Clean Air Act. Each of these pollutants has a national air quality standard set by EPA to protect public health:
- ground-level ozone
- particle pollution (also known as particulate matter, including PM2.5 and PM10)
- carbon monoxide
- sulfur dioxide
- nitrogen dioxide
What is the air quality scale?
The Air Quality Index, or AQI, is the U.S. Environmental Protection Agency’s system for reporting outdoor air pollution and its potential health effects. It covers five major pollutants, including ground-level ozone and particle pollution.
The AQI runs from 0 to 500 and uses six colors:
| AQI | Color | What it means |
|---|---|---|
| 0-50 | 🟢 Green | Good. Air pollution poses little or no risk. |
| 51-100 | 🟡 Yellow | Moderate. Acceptable for most people, though unusually sensitive people could be affected. |
| 101-150 | 🟠 Orange | Unhealthy for sensitive groups. People at greater risk may experience health effects. |
| 151-200 | 🔴 Red | Unhealthy. Some people in the general population may experience effects, with greater risks for sensitive groups. |
| 201-300 | 🟣 Purple | Very unhealthy. The risk of health effects increases for everyone. |
| 301-500 | 🟤 Maroon | Hazardous. Emergency-level conditions in which everyone is more likely to be affected. |
How it works in Cobb County
Cobb County residents may see the AQI in weather reports, apps or air quality forecasts for metro Atlanta. Current AQI readings can also change during the day as ozone or particle pollution levels change.
A key threshold is AQI 101, or orange. At that point, air quality is considered unhealthy for sensitive groups. Red and higher categories indicate increasingly broad health concerns.
Why it matters to residents
The AQI can help residents decide when to adjust outdoor exercise, yardwork, sports and other activities. On poorer-air-quality days, reducing the length or intensity of outdoor activity can reduce exposure.
The basic rule is simple: The higher the number and the farther the color moves from green toward maroon, the greater the health concern.
What to know now
For current conditions and forecasts, residents can check EPA’s AirNow, which reports the official U.S. AQI.