Instrument is not on line. The instrument is collecting data, but it has not been calibrated and the data it collects is ignored. Instrument is not on line. Automatic span check in progress. This is to check that the instrument calibration is holding. Span checks are generally performed once a week on each instrument and last from 2 to 4 hours. Non-scheduled span checks may be initiated at any time by TCEQ field operators - usually during the course of troubleshooting. Automatic span check in progress. Automatic calibration in progress. Calibrations are performed when instruments are changed or fail a span check and last from 3 to 6 hours. Non-scheduled calibrations may be initiated at any time by TCEQ field operators - usually during the course of instrument repair/replacement or troubleshooting. Automatic calibration in progress. Lost data. Usually indicates that data was never collected. This may also be triggered by delays or breakdowns in data communications. Try retrieving the data later. Lost data. Usually indicates that data was never collected. A malfunction that voids the data has occurred. The operator has determined that the data is not valid and should be ignored. Data voided by field operator. Data exceeds automatic criteria for rejection.<ul><li>For meteorological parameters, this indicates that the measurements fall outside the EPA guidelines for meteorological collection of data. This is usually due to a short-term meteorological condition, such as rapid heating during the day or extended periods of calm winds.<li>For pollution parameters, this indicates that the instrument failed a scheduled automatic calibration or span check. Calibrations are performed periodically to insure that the instrument is functioning properly and the data collected is valid. If a calibration is failed, TCEQ field operators will go to the monitoring station to determine why the automatic calibration failed. Once the problem has been identified and corrected, a fresh calibration will be done on the instrument and valid data will start being collected.</ul> Data exceeds automatic criteria for rejection. Quality Control audit in progress. TCEQ conducts periodic Quality Control audits on each monitoring site. Quality Control audit in progress. Preventive maintenance. Indicates the instument or monitoring site is undergoing maintenance and data collected is not valid data. Preventive maintenance. Data rejected by TCEQ validators. The TCEQ validators have reviewed the data and determined that it is not valid. Data rejected by TCEQ validators. Data rejected because of failed or poor quality assurance results. Data rejected because of failed or poor quality assurance results. Not enough five-minute measurements available to create an hourly average. There must be 45 minutes of data available each hour in order for a valid hourly average to be created. Not enough ambient five-minute samples have been collected to create a valid hourly average. The measurement exceeds a lower limit and has too negative a value. It is possible to get small negative values under routine conditions, but large negative numbers indicate a problem in the data collection system. The measurement exceeds a lower limit and has too negative a value. This is only seen on NOx monitors. This indicates that the sum of NO and NO₂ measured at a site does not balance with the amount of NO_x measured at a site. This usually indicates a problem in the instrument adjustment. This sum of NO and NO2 measured does not balance with the amount of NOx measured. Blank sample. Blank sample. Audit sample. Audit sample. Unblended standard check conducted at 5 ppb-V. Unblended standard check conducted at 5 ppb-V. Experimental or bad sample. Experimental or bad sample. 55-component standard sample. 55-component standard sample. Automatic span check in progress. This is a short instrument challenge to check that the instrument calibration is holding. These span checks are generally performed once a day on instruments and last 30 minutes. These are normally only seen if the system detects an instrument problem during the span check. Automatic span check in progress. Acetylene response check. Acetylene response check. Compressed air comparison sample. Compressed air comparison sample. Daily Cal check standard duplicate. Daily Cal check standard duplicate. Detection limit analysis. Detection limit analysis. Radian audit sample. Radian audit sample. Unknown flag found in data. Unknown flag found in data. Not Detected. The compound was not detected at a concentration that could be reliably quantitated. This may mean the compound is present but had interferences present, was below the detection capability of the instrument, or not present at all. Not Detected.