Eight-Hour Ozone High Value Days for 2021
as of April 13
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 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.
| 2021 Sorted by Maximum Value | |||||||
|---|---|---|---|---|---|---|---|
| Location | Region | CAMS | AQS | Date | Time | Value | POC |
| Lang C408 | 12 | 408 | 48_201_0047 | April 11 2021 | 11:00 | 89 | 2 |
| Houston Aldine C8/AF108/X150 | 12 | 8 | 48_201_0024 | April 11 2021 | 11:00 | 86 | 2 |
| Houston Harvard Street C417 | 12 | 417 | 48_201_0417 | April 11 2021 | 11:00 | 78 | 1 |
| Camp Bullis C58 | 13 | 58 | 48_029_0052 | April 11 2021 | 11:00 | 76 | 1 |
| Houston East C1/G316 | 12 | 1 | 48_201_1034 | April 11 2021 | 10:00 | 76 | 2 |
| UH Launch Trailer C1611 | 12 | 1611 | 48_201_1611 | April 11 2021 | 11:00 | 76 | 1 N |
| Houston North Wayside C405 | 12 | 405 | 48_201_0046 | April 11 2021 | 11:00 | 75 | 1 |
| Texas City 34th St. C620 | 12 | 620 | 48_167_0056 | March 23 2021 | 11:00 | 74 | 1 N |
| UH Moody Tower C695 | 12 | 695 | 48_201_0695 | April 11 2021 | 10:00 | 74 | 1 N |
| Conroe Relocated C78/A321 | 12 | 78 | 48_339_0078 | April 12 2021 | 10:00 | 73 | 1 |
| San Antonio Northwest C23 | 13 | 23 | 48_029_0032 | April 11 2021 | 11:00 | 72 | 2 |
| Bulverde Elementary C503 | 13 | 503 | 48_091_0503 | April 11 2021 | 11:00 | 72 | 1 N |
| Park Place C416 | 12 | 416 | 48_201_0416 | April 11 2021 | 11:00 | 72 | 1 |
| Meyer Park C561 | 12 | 561 | 48_201_0561 | April 11 2021 | 12:00 | 71 | 1 N |
| Dripping Springs School C614 | 11 | 614 | 48_209_0614 | April 11 2021 | 12:00 | 71 | 1 N |
| UH WG Jones Forest C698 | 12 | 698 | 48_339_0698 | April 12 2021 | 10:00 | 71 | 1 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
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.