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City of Stockton TL 394-0074-01 May 4, 1994 Page 13 ■ Analytical instruments are serviced on a regular basis to monitor accurate calibration; ■ Organic-free water will be monitored daily for quality; ■ Gas chromatographs will be calibrated daily; ■ Method blanks will be tested to check whether the glassware and reagents are free of interference from chemicals that would invalidate the analyses; and Standards will be prepared using the applicable reference materials. A-8 Standard Operating Procedures for Using Photoionization Detector PID and/or Drager® Tubes. The PID will be calibrated in accordance with the manufacture's recommendations prior to use in the field. Upon arrival at the project site, the PID will be used to monitor background concentrations of organic vapors in the atmosphere at the site. The background concentrations will be measured in a location upwind and removed as possible from sources of organic vapors on the site. When background concentrations of organic vapors register as "0.0" on the PID, subsequent readings of "0.0" registered from samples tested in the field will be recorded as WD" (not detected). When background concentrations of organic vapors register at some quantity above "0.0", subsequent readings registered from samples tested in the field at or below this value will be recorded as "B/G" (background). The Drager® tubes used will be consistent with the type of analyte which is suspected as being present on the project site (i.e. for gasoline product use the benzene tube, for diesel product use the petrol-hydrocarbon tube, etc.). Prior to use the tubes will be examined to insure the shelf life expiration date has not expired and the tube has not been opened or damaged. Tubes will only be use for one test. The Drager® Gas Detector Pump will be used with Drager®tubes to insure accuracy. Prior to use the pump will be examined to insure it is in proper operating condition. The tube will be opened and inserted into the pump just prior to use. The pump will be stroked the number of times required by the specific tube in use (i.e. 2 strokes for the petrol-hydrocarbon tube). After each stroke the pump will be allowed to open to the full extent of the arrestor chain (10 to 20 seconds). If the analyte is present in the sample, the material within the tube will discolor. The extent of the discolored material corresponds to the concentration of the analyte present. Readings from the tube will be recorded based upon the amount of discolored material read from the calibrated markings on the tube. In the event the discoloration should extend beyond one marking but not to the next, this will be recorded as greater than (>)"the lower value. (i.e. if the discoloration extends beyond 300 ppm but does not reach 500 ppm, this would be