Eight-Hour Ozone High Value Days for 2015
as of February 27

The table below lists the daily maximum eight-hour ozone concentrations measured which meet or exceed 76 parts per billion in 2015 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.

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Year	Sort By	Report Format
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015	RegionLocationCAMS NumberAQS NumberDateMaximum Value	Tabular (Web Formatted)Comma-Delimited
Highlight with AQI colors

2015 Sorted by Maximum Value
Location	Region	CAMS	AQS	Date	Time	Value	POC
No values meet or exceed 76 ppb for 2015
No sites report 8-hour ozone concentrations meeting or exceeding 76 parts per billion for 2015.
POC (Parameter Occurrence Code): a code used to correctly separate data from multiple instruments at one site.

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 - 0.059
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

• 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 beginning 1/1/2013, 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.