Air Quality Index

The Air Quality Index (AQI) is a color-coded scale used to effectively communicate the health impacts of air quality.  Higher AQI values mean greater health concern since there is more outdoor air pollution.   AQI values higher than 100 exceed the health-based standards set by the Environmental Protection Agency (EPA).

A daily AQI value is calculated for each monitored criteria​ pollutant: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide.  The pollutant with the highest AQI value is reported for that particular day.  For the Charlotte area, ground-level ozone usually has the highest AQI during the summer months and particulate matter usually has the highest AQI during the remainder of the year.

What do the colors mean?

When the AQI Color Code is green or yellow, the air quality is considered acceptable and is not expected to have widespread health impacts.

When the AQI Color Code is orange, sensitive groups may experience negative health impacts.  Sensitive groups include people with lung or heart disease, older adults, active people, and children.

When the AQI Color Code is red or purple, the general public is likely to experience negative health impacts.

AQI Basics for Ozone and Particle Pollution

Daily AQI ColorLevels of ConcernValues of IndexDescription of Air Quality
GreenGood0 to 50Air quality is satisfactory, and air pollution poses little or no risk.
YellowModerate51 to 100Air quality is acceptable. However, there may be a risk for some people, particularly those who are unusually sensitive to air pollution.
OrangeUnhealthy for Sensitive Groups101 to 150Members of sensitive groups may experience health effects. The general public is less likely to be affected.
RedUnhealthy151 to 200Some members of the general public may experience health effects; members of sensitive groups may experience more serious health effects.
PurpleVery Unhealthy201 to 300Health alert: The risk of health effects is increased for everyone.
MaroonHazardous301 and higherHealth warning of emergency conditions: everyone is more likely to be affected.

How can I protect my health on bad air quality days?

To protect your health on Code Orange, Red, or Purple days, you should limit prolonged or heavy exertion outdoors, especially in the afternoon hours when air quality is typically worse.  Your exposure to air pollution depends on the length of time and level of exertion.  Any activity that increases your breathing rate also increases your risk of exposure to air pollution.  You don't need to stay indoors, but "take it easy" outdoors to reduce your risk. 

How do I get the Air Quality Forecast?

The AQI is forecasted daily, just like the weather!  You can get the AQI forecast from the Mecklenburg County Air Quality homepage or the EPA A​​irNow website. You can also subscribe to email or text notifications at the EPA EnviroFlash website.  Check your local TV or newspaper weather report, especially in the summer months.