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Four Highest Eight-Hour Ozone Concentrations in 2019
as of August 23

Use this form to retrieve the four highest eight-hour ozone concentration averages from data collected at Virginia DEQ monitoring sites beginning January 1, 2012 through today. Although this is our most current data, it is not considered official until it has been certified by our technical staff. This information is updated hourly. All times shown are in Local Standard Time.

The table below lists the four highest daily maximum eight-hour ozone concentrations measured in 2019 in each community where the Virginia DEQ measures ozone. Concentrations that are rated Moderate or higher are color-highlighted based on the EPA-defined Air Quality Index colors. (See Interpreting the AQI.) The fourth-highest average is in bold black (unless it is highlighted). All ozone measurements are in parts per billion. Times are shown in 24-hour format and correspond to the beginning of the eight hour average.

Use the selection boxes below to customize this report. You may select a different year or a different report format. If you want to cut and paste data from this web page into another application, such as a spreadsheet, select the comma-delimited format. Click on the Generate Report button once you have made your selections.

YearReport Format
Highlight with AQI colors
Area Monitoring Site POC Highest Second Highest Third Highest Fourth Highest
Date Time Value Date Time Value Date Time Value Date Time Value
Rural Retreat104/04/201912006104/03/201910005804/17/201909005703/29/2019090057
Albemarle High School103/30/201912006004/04/201913005803/29/201911005804/17/2019100057
Frederick Co. Public School Maint. Dept.106/08/201911006103/30/201912005708/06/201910005505/07/2019100055
Natural Bridge Station103/29/201911006104/17/201912005904/03/201910005804/04/2019110057
Harrisonburg VDOT106/27/201909005805/16/201909005604/03/201910005503/30/2019100055
Blue Ridge
Herman L. Horn Elementary School103/29/201910006104/17/201911006007/14/201910005904/04/2019120059
Charles City County106/26/201911006506/27/201911006208/01/201909006107/13/2019100058
Beach Road VDOT106/27/201909006608/03/201910005907/26/201909005903/29/2019100058
MSIC (MathScience Innovation Center)108/01/201909007006/27/201911007008/18/201910006405/18/2019110064
NASA Langley Research Center106/27/201909006506/26/201910006105/24/201913006105/16/2019100061
Tidewater Community College106/27/201910006906/26/201910006108/01/201911006005/24/2019130059
VA Tech Agricultural Research Center104/25/201911005905/18/201912005805/16/201910005804/17/2019110057
Aurora Hills Visitor Center106/27/201909007406/28/201910006906/01/201912006907/30/2019090068
Fredericksburg Geomagnetic Observatory107/30/201910006106/27/201909006103/30/201911006003/29/2019110059
Lee District Park - Fairfax County108/01/201911007206/01/201912007106/27/201908006906/28/2019100068
Sumerduck - C. Phelps Wildlife Mgmt Area103/30/201912005904/17/201912005604/04/201911005508/05/2019110053
Ashburn - Broad Run High School108/20/201909007407/27/201910006306/27/201909006208/02/2019090060
Shenandoah National Park - Big Meadows104/17/201913006003/30/201910006006/05/201901005906/04/2019220059
Long Park - Haymarket108/20/201910007007/26/201911006308/05/201911006006/08/2019100060
Widewater Elem. School - Widewater107/30/201908006003/30/201911006007/26/201909005906/01/2019100059
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.