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Eight-Hour Ozone High Value Days for 2021
as of June 12

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
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
Michigan City-W. Michigan Blvd 1 1618_091_0005June 11 202111:00721
Granger-Beckley St 2 7418_141_0016June 4 202112:00721
Michigan City-W. Michigan Blvd 1 1618_091_0005June 4 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.