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Four Highest Eight-Hour Ozone Concentrations in 2021
as of September 20

Use this form to retrieve the four highest eight-hour ozone concentration averages from data collected at IDEM monitoring sites beginning December 14, 2005 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 2021 in each community where the IDEM 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
North West
Hammond-141st St106/03/202110007607/20/202110007406/18/202110007008/25/2021110068
Ogden Dunes106/03/202110008106/18/202110007907/20/202110007308/25/2021100072
Michigan City-W. Michigan Blvd106/03/202111008306/18/202111007906/11/202111007206/04/2021100071
LaPorte-E. Lincolnway106/03/202112007806/18/202110007106/04/202111006807/27/2021100064
North Central
South Bend-Shields Dr106/18/202113006906/03/202112006906/04/202112006707/27/2021120066
Potato Creek State Park106/18/202111006806/03/202110006806/04/202111006506/17/2021120062
Granger-Beckley St106/04/202112007206/03/202111006906/18/202112006707/27/2021120066
North East
Fort Wayne-Beacon St106/17/202110006406/18/202114005906/12/202111005906/04/2021120059
Leo HS106/17/202111007006/04/202112006906/05/202111006606/18/2021140065
West Central
Terre Haute-Lafayette Ave106/17/202112006306/14/202110006306/04/202111006305/24/2021120062
West Union106/14/202109006506/04/202110006406/18/202110006206/17/2021110062
East Central
Anderson-Eastside Elem. School206/04/202112006906/17/202111006806/14/202109006506/12/2021100065
Indpls-Washington Park107/27/202111006906/12/202110006607/26/202110006506/16/2021120065
Indpls-Harding St106/12/202111006807/27/202111006707/26/202110006706/16/2021120063
Indpls-Ft. Harrison107/27/202110006906/17/202111006906/04/202111006906/16/2021120066
Noblesville-191st St106/17/202112007006/04/202112006806/12/202111006706/14/2021090065
Indpls - I-70 E106/17/202111006206/12/202110006206/04/202112006005/24/2021110060
Kokomo - E. Vaile Ave.106/12/202110007206/18/202114007106/11/202113006506/14/2021080064
South West
Evansville-Buena Vista Rd106/17/202110006606/14/202112006507/23/202110006406/04/2021110064
St. Philips106/14/202111006306/04/202110006206/18/202112006006/17/2021100059
South East
New Albany108/26/202111007006/14/202112006706/04/202111006507/27/2021110064
Charlestown State Park106/04/202112006806/17/202111006708/24/202110006606/14/2021130063
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 0.201 - 0.2011
401 - 500 0.505 - 0.604 Not Defined
500+ Not Defined Not Defined

PLEASE NOTE: This data has not been verified by the IDEM 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 IDEM 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.