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Eight-Hour Ozone High Value Days for 2017
as of December 12

The table below lists the daily maximum eight-hour ozone concentrations measured which meet or exceed 71 parts per billion in 2017 in each community where the DAQ 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.

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YearSort ByReport Format
Highlight with AQI colors
2017 Sorted by Maximum Value
LocationRegionCAMSAQSDateTimeValuePOC
Walter Johnson 1 7132_003_0071June 23 201710:00871
Joe Neal 1 7532_003_0075July 4 201709:00801
Walter Johnson 1 7132_003_0071July 7 201709:00791
Joe Neal 1 7532_003_0075June 22 201709:00771
Joe Neal 1 7532_003_0075June 23 201711:00771
Paul Meyer 1 4332_003_0043August 31 201709:00761
Walter Johnson 1 7132_003_0071July 4 201709:00761
Palo Verde 1 7332_003_0073June 23 201710:00761
Palo Verde 1 7332_003_0073July 7 201709:00761
Joe Neal 1 7532_003_0075July 15 201710:00761
Walter Johnson 1 7132_003_0071June 30 201711:00751
Palo Verde 1 7332_003_0073June 16 201709:00751
Joe Neal 1 7532_003_0075June 30 201711:00751
Joe Neal 1 7532_003_0075July 7 201710:00751
Joe Neal 1 7532_003_0075August 5 201710:00751
JD Smith 1 200232_003_2002June 23 201711:00751
JD Smith 1 200232_003_2002July 4 201709:00751
Walter Johnson 1 7132_003_0071July 11 201710:00741
Walter Johnson 1 7132_003_0071July 12 201709:00741
Palo Verde 1 7332_003_0073July 12 201709:00741
Joe Neal 1 7532_003_0075June 16 201710:00741
Joe Neal 1 7532_003_0075June 28 201710:00741
Apex 1 2232_003_0022July 11 201710:00731
Walter Johnson 1 7132_003_0071June 16 201710:00731
Walter Johnson 1 7132_003_0071June 22 201709:00731
Walter Johnson 1 7132_003_0071August 31 201710:00731
Palo Verde 1 7332_003_0073June 22 201708:00731
Palo Verde 1 7332_003_0073July 4 201708:00731
Joe Neal 1 7532_003_0075June 14 201711:00731
Joe Neal 1 7532_003_0075July 12 201708:00731
Green Valley 1 29832_003_0298July 11 201709:00731
JD Smith 1 200232_003_2002August 31 201710:00731
Walter Johnson 1 7132_003_0071June 17 201709:00721
Walter Johnson 1 7132_003_0071July 15 201709:00721
Palo Verde 1 7332_003_0073June 30 201711:00721
Joe Neal 1 7532_003_0075June 17 201709:00721
Joe Neal 1 7532_003_0075July 14 201709:00721
Green Valley 1 29832_003_0298June 17 201709:00721
JD Smith 1 200232_003_2002July 7 201710:00721
Apex 1 2232_003_0022June 28 201710:00711
Paul Meyer 1 4332_003_0043June 23 201710:00711
Paul Meyer 1 4332_003_0043July 12 201709:00711
Walter Johnson 1 7132_003_0071May 23 201711:00711
Walter Johnson 1 7132_003_0071August 5 201710:00711
Joe Neal 1 7532_003_0075July 8 201709:00711
Joe Neal 1 7532_003_0075July 13 201709:00711
Green Valley 1 29832_003_0298August 31 201710:00711
JD Smith 1 200232_003_2002June 16 201710:00711
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 Clark County Department of Air Quality 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 Clark County Department of Air Quality 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.