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Air Quality Index


 Small Air Quality Index

 Air Quality Index

"A guide to air quality and your health"

Last updated November 7, 2014 at 6:30 a.m.


Local air quality affects how we live and breathe. Like the weather, it can change from day to day or even hour to hour. The U.S. Environmental Protection Agency (EPA) and others are working to make information about outdoor air quality as available to the public as information about the weather. A key tool in this effort is the Air Quality Index or AQI. USEPA and the WVDEP-Division of Air Quality use this standardized system to provide the public with timely and easy-to-understand information on local air quality and whether air pollution levels pose a health concern.



Critical Pollutant






Greenbrier County
































Please note: Data in the table is collected from WVDAQ air monitoring sites. This information has not been verified by the WVDAQ and may change. While this is the most current data, it is not official until it has been certified by the appropriate technical staff.       "****" = data not available. WV Ozone Season = April 1 - October 31.

The AQI is reported on this website by the West Virginia DEP - Division of Air Quality. The table above lists the AQI for West Virginia cities where daily monitoring data is recorded. The current AQI rating, the critical pollutant, and the current peak concentration  for the pollutant as based on the National Ambient Air Quality Standards (NAAQS) are listed.

The reported AQI is the calculated value for the past 24 hours in that area and, dependent upon each monitoring site, measures concentrations of five criteria pollutants: carbon monoxide, ozone, sulfur dioxide, PM2.5 and PM10.


Interpreting the AQI

USEPA uses the AQI for five major pollutants regulated by the Clean Air Act – ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide and nitrogen dioxide. For each of these pollutants, USEPA has established a scale based on the NAAQS to protect against harmful health effects.


AQI Colors Table


AQI Colors

To make it easier for people to understand quickly the significance of air pollution levels in their communities, USEPA has divided the AQI scale into six levels of health concern and assigned a specific color to each category:

  • "GOOD" The AQI value for your community is between 0 and 50. Air quality is considered satisfactory and air pollution poses little or no risk. No cautionary actions are needed.
  • "MODERATE" The AQI for your community is between 51 and 100. Air quality is acceptable, however, unusually sensitive people should consider limiting prolonged outdoor exertion.
  • "UNHEALTHY FOR SENSITIVE GROUPS" Certain groups of people are particularly sensitive to the harmful effects of certain air pollutants. This means they are likely to be affected at lower levels than the general public. For example, children and adults who are active outdoors and people with respiratory disease are at greater risk from exposure to ozone, while people with heart disease are at greater risk from carbon monoxide. Some people may be sensitive to more that one pollutant. When AQI values are between 101 and 150, members of sensitive groups may experience health effects. The general public is not likely to be affected when the AQI is in this range.
  • "UNHEALTHY" AQI values are between 151 and 200. Everyone may begin to experience health effects. Active children and adults, and people with respiratory disease, such as asthma, should avoid prolonged outdoor exertion; everyone else, especially children, should limit prolonged outdoor exertion.
  • "VERY UNHEALTHY" AQI values between 201 and 300 trigger a health alert, meaning everyone may experience more serious health effects. Active children and adults, and people with respiratory disease, such as asthma, should avoid all outdoor exertion; everyone else, especially children, should limit outdoor exertion.
  • "HAZARDOUS" AQI values over 300 trigger health warnings of emergency conditions. The entire population is more likely to be affected. Everyone should avoid all outdoor exertion.

You may also see these colors when the AQI is reported in the newspaper or on television. The colors can help you rapidly determine whether air pollutants are reaching unhealthy levels in your area.


Real-Time Data


Due to computer security restraints, the AQI must be manually updated by DAQ staff and is not available on the weekends. However, our monitoring sites are linked with the U.S. Environmental Protection Agency's AIRNOW network, and provides an hourly update from 7 a.m. to 9 p.m. daily.


Monitoring Stations

West Virginia maintains a Statewide network for monitoring air quality. Air quality is measured by networks of monitors that record the concentrations of the major pollutants. These raw measurements are then converted into AQI values using standard formulas developed by USEPA. An AQI value is calculated for each of the individual NAAQS pollutants (ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide and nitrogen dioxide) in an area.

Data from monitoring stations located in Charleston, Greenbrier County, Huntington, Martinsburg, Morgantown, Parkersburg, Weirton and Wheeling is used to determine the AQI for those areas. Monitoring stations are equipped with computerized technical instruments.


National Ambient Air Quality Standards (NAAQS)

Air quality standards – known as National Ambient Air Quality Standards (NAAQS) – were established for acceptable concentrations of specific pollutants in the ambient (outdoor) air. These standards were set by the USEPA for pollutants which have adverse effects on human health and welfare. Two standards were established for each pollutant. Primary standards were set according to criteria designed to protect public health, including an adequate margin of safety to protect sensitive populations such as children and the elderly. The second standards were set according to criteria designed to protect public welfare (decreased visibility, damage to crops, vegetation, buildings, etc.).

Five principal pollutants currently have NAAQS: carbon monoxide (CO), nitrogen dioxide (NO2), ground-level ozone (O3), particulate matter (PM10 and PM2.5), and sulfur dioxide (SO2).  These are commonly called the "criteria pollutants."

Health effects of air pollution vary greatly, depending on the exposure level, duration and pollutant. The air quality standard is expressed as an average concentration over a specific time period (an hour, a day, or a year, for example) to account for the fact that the concentration of a pollutant in air varies over time. The concentration is expressed in parts per million (ppm) or micrgrams of pollutant per cubic meter of air (µg/m3). The standard also specifies whether the limit applies to an annual average concentration, a particular percentile or a number of times the level can be exceeded during the calendar year.

These standards are described in the Code of Federal Regulations, Part 58, Appendix G.


Additional Links


US EPA Air Quality Index(AQI) - AIRNow

Air Quality Index (AQI): A Guide to Air Quality and Your Health

Clean Indoor Air

It all adds up to cleaner air

United States Air Quality Trends

   Kid's Air 


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