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Eight-Hour Ozone High Value Days for 2021
as of September 20

The table below lists the daily maximum eight-hour ozone concentrations measured which meet or exceed 71 parts per billion in 2021 in each community where the IDEM 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
2021 Sorted by Maximum Value
LocationRegionSite CAMSAQSDateTimeValuePOC
Michigan City-W. Michigan Blvd 1 1618_091_0005June 3 202111:00831
Ogden Dunes 1O Dunes 1318_127_0024June 3 202110:00811
Valparaiso 1 2818_127_0026June 3 202111:00801
Michigan City-W. Michigan Blvd 1 1618_091_0005June 18 202111:00791
Ogden Dunes 1O Dunes 1318_127_0024June 18 202110:00791
LaPorte-E. Lincolnway 1 3418_091_0010June 3 202112:00781
Gary-IITRI 1 3118_089_0022June 3 202110:00761
Hammond-141st St 1 618_089_2008June 3 202110:00761
Gary-IITRI 1 3118_089_0022June 18 202110:00751
Hammond-141st St 1 618_089_2008July 20 202110:00741
Valparaiso 1 2818_127_0026June 18 202110:00741
Ogden Dunes 1O Dunes 1318_127_0024July 20 202110:00731
Valparaiso 1 2818_127_0026July 20 202110:00731
Flora 4 3618_015_0002June 12 202110:00721
Kokomo - E. Vaile Ave. 5 7918_067_0004June 12 202110:00721
Gary-IITRI 1 3118_089_0022July 20 202110:00721
Michigan City-W. Michigan Blvd 1 1618_091_0005June 11 202111:00721
Ogden Dunes 1O Dunes 1318_127_0024August 25 202110:00721
Granger-Beckley St 2 7418_141_0016June 4 202112:00721
Boonville 6 1218_173_0008July 28 202110:00721
Kokomo - E. Vaile Ave. 5 7918_067_0004June 18 202114:00711
Michigan City-W. Michigan Blvd 1 1618_091_0005June 4 202110:00711
LaPorte-E. Lincolnway 1 3418_091_0010June 18 202110:00711
Dayville 6 5218_173_0011July 28 202110:00711
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 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.