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Eight-Hour Ozone High Value Days for 2017
as of October 20

The table below lists the daily maximum eight-hour ozone concentrations measured which meet or exceed 76 parts per billion in 2017 in each community where the TREX 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
2017 Sorted by Maximum Value
LocationRegionCAMSAQSDateTimeValuePOC
Fort McDowell Yuma Frank-AZ 9 103004_013_1030June 14 201712:00841 N
POC (Parameter Occurrence Code): a code used to correctly separate data from multiple instruments at one site.
 N - Data from this instrument does not meet EPA quality assurance criteria and cannot be used for regulatory purposes.

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 - 0.059
51 - 100 Not Defined 0.06 - 0.075
101 - 150 0.125 - 0.164 0.076 - 0.095
151 - 200 0.165 - 0.204 0.096 - 0.115
201 - 300 0.205 - 0.404 0.116 - 0.374
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 TREX 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 TREX 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.