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This web page provides the most current hourly measurement data available. Our convention for time-tagging data is the beginning of each hour. For example, values shown for the noon hour represent a sample collected during the noon hour (noon to 1:00 p.m) and then analyzed at the site during the following hour (1:00 p.m. to 2:00 pm). The noon values will not be available from the site until after 2:00 p.m. This results in an apparent two hour time lag in the data. We also present our data in Local Standard Time for each measuring site regardless of Daylight Savings Time Observance. For most of Texas this is Central Standard Time (sites in El Paso will be in Mountain Standard Time). During Daylight Savings, this introduces another apparent one hour time lag in the data.
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.