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Four Highest Eight-Hour Ozone Concentrations in 2018
as of April 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 2018 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 Retreat104/13/201813006404/18/201810006103/15/201818005704/12/2018120056
Albemarle High School104/13/201812006804/12/201813005904/06/201813005903/29/2018140056
Frederick Co. Public School Maint. Dept.104/13/201811006204/14/201809005703/19/201810005204/10/2018100050
Natural Bridge Station104/13/201813006704/18/201814006104/12/201813005704/06/2018110057
Harrisonburg VDOT104/13/201811006204/12/201812005404/06/201810005304/14/2018080052
Blue Ridge
Herman L. Horn Elementary School104/13/201812006604/18/201814006104/12/201812005604/17/2018120055
Charles City County104/13/201811005904/06/201811005904/12/201811005304/11/2018100050
Beach Road VDOT104/13/201811006004/06/201811005804/12/201814005704/11/2018100052
MSIC (MathScience Innovation Center)104/13/201810005804/06/201811005704/12/201813005504/11/2018100051
NASA Langley Research Center104/06/201812005504/11/201810005404/13/201810005304/12/2018100052
Tidewater Community College104/06/201810005704/13/201810005504/12/201810005304/11/2018090049
VA Tech Agricultural Research Center104/06/201811005804/12/201811005504/13/201810005404/11/2018100054
Aurora Hills Visitor Center104/13/201812006504/06/201813005604/12/201812005404/14/2018100051
Fredericksburg Geomagnetic Observatory104/13/201811006404/06/201812005904/12/201814005604/11/2018110053
Lee District Park - Fairfax County104/13/201811006404/06/201813005604/12/201812005504/11/2018110053
Sumerduck - C. Phelps Wildlife Mgmt Area104/13/201814006204/12/201814005804/06/201813005804/11/2018100053
Ashburn - Broad Run High School104/13/201813006404/12/201815005804/06/201813005604/14/2018100052
Shenandoah National Park - Big Meadows104/13/201813006704/12/201814005704/06/201811005604/18/2018160055
Long Park - Haymarket104/13/201812006504/12/201815005904/14/201810005204/11/2018100052
Widewater Elem. School - Widewater104/13/201811006404/12/201812005504/06/201813005504/10/2018110053
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.