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Four Highest Eight-Hour Ozone Concentrations in 2019
as of February 19

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 Retreat102/14/201912004302/04/201910004302/16/201909004202/02/2019100041
Albemarle High School102/15/201919004202/13/201912004002/08/201907004002/03/2019120040
Frederick Co. Public School Maint. Dept.102/15/201918004001/20/201914003902/16/201910003801/25/2019100037
Natural Bridge Station102/15/201919004302/04/201911004202/16/201901003902/14/2019210039
Harrisonburg VDOT102/15/201919004302/13/201915004002/08/201909004001/30/2019120039
Blue Ridge
Herman L. Horn Elementary School102/15/201921004402/04/201911004402/13/201910004202/16/2019010041
Charles City County102/08/201911004402/15/201912004302/13/201910004002/04/2019110040
Beach Road VDOT102/08/201911004602/15/201913004402/03/201909004402/14/2019100042
MSIC (MathScience Innovation Center)102/04/201909004302/08/201910004102/15/201910004002/13/2019090039
NASA Langley Research Center102/15/201911004502/08/201912004402/04/201910004302/14/2019200042
Tidewater Community College102/15/201909004402/08/201911004302/06/201911004302/14/2019180040
VA Tech Agricultural Research Center102/15/201911004602/06/201912004602/04/201910004602/05/2019100044
Aurora Hills Visitor Center102/15/201921004102/16/201901003801/20/201917003802/19/2019040036
Fredericksburg Geomagnetic Observatory102/04/201914004502/15/201910004202/08/201912004202/16/2019010040
Lee District Park - Fairfax County102/15/201909004002/04/201911003901/20/201916003902/16/2019110038
Sumerduck - C. Phelps Wildlife Mgmt Area102/04/201913004202/15/201909003902/08/201912003802/03/2019130038
Ashburn - Broad Run High School102/15/201920004302/16/201911004101/20/201914003902/13/2019130038
Shenandoah National Park - Big Meadows102/04/201916004902/15/201918004502/14/201907004502/03/2019050045
Long Park - Haymarket102/15/201919004101/20/201915004002/16/201910003902/19/2019050038
Widewater Elem. School - Widewater102/16/201913004102/15/201909004102/08/201912004102/14/2019120038
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.