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ANALYTICAL METHODOLOGY <br /> Oxygen Concentrations in Soil Vapor <br /> Instrument: <br /> On-site Gas chromatograph. <br /> Method <br /> ASTM method 1945-96. Fixed gases by GC-TCD. <br /> Instrument Initial Multipoint Calibration <br /> The instrument is calibrated prior to arrival on-site. <br /> Daily Continuing Calibration <br /> Continuing Calibration is performed at the start of each day and end of each <br /> day by measuring outside air. Acceptable continuing calibration agreement: <br /> +/- 20% to the known outside air value of 20.8%. <br /> Blanks <br /> Pure nitrogen (oxygen free) is analyzed at the start of each day and during <br /> the day as appropriate depending upon the measured concentrations. <br /> ©Hartman Environmental Geoscience 2011 3 <br />