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Eight-Hour Ozone High Value Days for 2018
as of December 11

The table below lists the daily maximum eight-hour ozone concentrations measured which meet or exceed 71 parts per billion in 2018 in each community where the Virginia DEQ measures ozone. This information is updated hourly. Concentrations are color-highlighted based on the EPA-defined Air Quality Index colors. (See Interpreting the AQI.) Times shown are in 24-hour format and are Local Standard Time. Our convention is that the time reflects the beginning of the eight-hour average. All ozone measurements are in parts per billion.

Use the selection boxes below to customize this report. You may select a different year, a different sorting order, or a different report format. Click on the Generate Report button once you have made your selections.

YearSort ByReport Format
Highlight with AQI colors
2018 Sorted by Maximum Value
LocationRegionSite CAMSAQSDateTimeValuePOC
MSIC (MathScience Innovation Center) 472-M 1951_087_0014June 30 201811:00841
Aurora Hills Visitor Center 647-T 1151_013_0020July 9 201811:00771
Widewater Elem. School - Widewater 644-A 2751_179_0001July 12 201810:00741
Aurora Hills Visitor Center 647-T 1151_013_0020July 3 201809:00721
Charles City County 475-B 1351_036_0002June 18 201812:00721
Aurora Hills Visitor Center 647-T 1151_013_0020June 30 201810:00711
Lee District Park - Fairfax County 646-B9 1551_059_0030May 24 201812:00711
POC (Parameter Occurrence Code): a code used to correctly separate data from multiple instruments at one site.

Interpreting the AQI

Air Quality Index

Each NAAQS pollutant has a separate AQI scale, with an AQI rating of 100 corresponding to the concentration of the Federal Standard for that pollutant. Additional information about the AQI and how it can be used is available from the EPA's AirNow web site.

Place your mouse pointer over the scale displayed above to view information about the Air Quality Index, and each of the rating levels.

The actual index calculation is different for each parameter measured and is specified by the EPA. The following table shows the various breakpoints used in calculating the AQI.

AQI Breakpoint Definitions
AQI Range 1hr Ozone
in ppm
8hr Ozone
in ppm
0 - 50 Not Defined 0 - 0.054
51 - 100 Not Defined 0.055 - 0.070
101 - 150 0.125 - 0.164 0.071 - 0.085
151 - 200 0.165 - 0.204 0.086 - 0.105
201 - 300 0.205 - 0.404 0.106 - 0.200
301 - 400 0.405 - 0.504 Not Defined
401 - 500 0.505 - 0.604 Not Defined
500+ Not Defined Not Defined

PLEASE NOTE: This data has not been verified by the Virginia DEQ and may change. This is the most current data, but it is not official until it has been certified by our technical staff. Data is collected from Virginia DEQ ambient monitoring sites and may include data collected by other outside agencies. This data is updated hourly. All times shown are in local standard time unless otherwise indicated.