Ozone Average Values

Ozone monitoring sites are located in 30 North Carolina counties and operated by state, local, federal and Tribal Governments.  For ozone, the United States Environmental Protection Agency (USEPA) defines the Design Value as the 4th-highest daily maximum 8-hour average concentration, averaged over a 3-year period.  For more detailed information on how the design value is calculated, please see 40 CFR Part 50, Appendix U.

In 2015, USEPA strengthened the NAAQS for ozone to 0.070 parts per million, or ppm.  Any design value above this level is considered non-attainment of the standard.  There are currently no counties in North Carolina in non-attainment.

To view ozone design values by county, please select the desired time period below.