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Eight-Hour Ozone High Value Days for 2017
as of April 23

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 TCEQ 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
Huffman Wolf Road C563 12 56348_201_0563March 15 201721:001771 N
Huffman Wolf Road C563 12 56348_201_0563March 16 201700:001651 N
Conroe Relocated C78/A321 12 7848_339_0078April 7 201711:00811
UH WG Jones Forest C698 12 69848_339_0698April 7 201712:00791 N
Baytown Garth C1017 12 101748_201_1017April 7 201711:00781
UH West Liberty C699 12 69948_291_0699April 7 201711:00781 N
Wallisville Road C617 12 61748_201_0617April 7 201710:00751 N
Galveston 99th St. C1034/A320/X183 12 103448_167_1034April 7 201710:00721
Killeen Skylark Field C1047 9 104748_027_1047April 7 201711:00711
HRM-3 Haden Road C603/A114 12 60348_201_0803April 7 201710:00711 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 - 0.054
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 Not Defined
401 - 500 Not Defined Not Defined
500+ Not Defined Not Defined

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

Following EPA reporting guidelines, negative values may be displayed in our hourly criteria air quality data, down to the negative of the EPA listed Method Detection Limit (MDL) for the particular instrument that made the measurements. The reported concentrations can be negative due to zero drift in the electronic instrument output, data logger channel, or calibration adjustments to the data. Prior to 1/1/2013, slightly negative values were automatically set to zero.