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One-Hour Ozone High Value Days for 2018
as of August 17

In July 1997, the U. S. Environmental Protection Agency (EPA) announced a new National Ambient Air Quality Standard for ground-level ozone. The EPA is phasing out and replacing the previous one-hour standard with a new eight-hour standard to protect public health against longer exposure to the air pollutant.

A community will meet the new standard when the three-year average of the fourth-highest daily maximum eight-hour concentration measured at each monitoring site is less than 85 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. All times shown are in 24-hour format and are Local Standard Time. These times correspond to the beginning of the hourly average.

YearSort ByReport Format
Highlight with AQI colors
The table below lists the one-hour ozone concentrations measured in 2018 in each community where TCEQ measures ozone that are equal to or higher than 125 parts per billion. All ozone measurements are in parts per billion. Concentrations are color-highlighted based on the EPA-defined Air Quality Index colors. (See Interpreting the AQI.)

2018 -- Sorted by Maximum Value
LocationRegionCAMSAQSDateTimeValuePOCHours
Exceeded
SETRPC Port Arthur C6281062848_245_0628July 10 201813:001521 N1
Houston Aldine C8/AF108/X150 12848_201_0024July 27 201815:0014422
Lynchburg Ferry C1015/A165 12101548_201_1015July 27 201812:0013811
Cleburne Airport C77/C68247748_251_0003July 23 201815:0013711
HRM-3 Haden Road C603/A114 1260348_201_0803July 27 201813:001351 N1
Channelview C15/AH115 121548_201_0026July 27 201813:0013231
Houston East C1/G31612148_201_1034July 27 201814:0013021
Northwest Harris Co. C26/A110/X154122648_201_0029July 27 201818:0012822
Lang C4081240848_201_0047July 27 201816:0012821
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.

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.

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
  • The AQI for ozone is based on either the peak eight-hour running average since midnight OR the peak one-hour measurement since midnight.

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.