Credit: EPA
The federal Environmental Protection Agency has noted their color-coded scale for the Air Quality Index, from Code Green (Good) to Code Maroon (Hazardous).

MEMPHIS, Tenn. — The Shelby County Health Department has issued a Code Orange Ozone Alert for Shelby, Crittenden, and Desoto County for Thursday. This ozone forecast is due to forecasted ozone values that will be unhealthy for sensitive groups. DeSoto county reports they are in the Yellow zone.

What does a Code Orange Air Quality Alert actually mean?

According to the Environmental Protection Agency, the Air Quality Index is measured on a 500-point scale.

The values on that scale are also tied to a six-point, color-coded system — from Code Green (Good) to Code Maroon (Hazardous).  

Each category corresponds to a measure of air quality that helps determine the level of health concern.



  • When the Air Quality Index is between 0 and 50, conditions are considered Good and are listed as Code Green. In this category, air pollution poses little or no risk.
  • With an Air Quality Index between 51 and 100, conditions are listed as Code Yellow and are considered Moderate. Air quality is considered acceptable, but there may be a moderate concern for a small number of people.
  • An Air Quality Index of 101 to 150 brings Code Orange conditions. The air is considered Unhealthy for Sensitive Groups. People with lung disease, older adults and children are at greater risk from exposure to ozone, whereas persons with heart and lung disease, older adults and children are at greater risk from the presence of particles in the air.
  • An Air Quality Index of 151 to 200 will result in Code Red conditions. At that point, the air is considered Unhealthy. Everyone may begin to experience some adverse health effects, and members of the sensitive groups may experience more serious effects
  • When the Air Quality Index is 201 to 300, the conditions hit Code Purple and termed Very Unhealthy. This would trigger a health alert signifying that everyone may experience more serious health effects.
  • With an Air Quality Index of 301-500, conditions are at Code Maroon and considered Hazardous. This condition would trigger a health warning of emergency conditions. The entire population would be more likely to be affected by these conditions.

According to the EPA, the air quality is a measure tied to five major air pollutants that are regulated by the Clean Air Act: ground-level ozone, particle pollution — or particulate matter, carbon monoxide, sulfur dioxide and nitrogen dioxide

.Air Quality Index (AQI) Basics is an index for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be a concern for you. The AQI focuses on health effects you may experience within a few hours or days after breathing polluted air. For further information, you can visit

There are two types of ozone as defined by the EPA – ozone in the upper atmosphere, or “stratospheric ozone” is “good” ozone, because it protects us from ultraviolet radiation from the sun. Ground-level ozone is considered “bad” because it can trigger various health problems, particularly for children, the elderly and those who have health problems like asthma.