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ITO E RO E K SOP No.026,REV.1 <br /> ASSOCIATES,INC INDOOR AIR AND SUB-SLAB SOIL GAS SAMPLING METHODS <br /> PAGE 13 <br /> Each duplicate is collected in conjunction with a corresponding environmental sample. <br /> To collect duplicate samples in canisters, a Swagelok"T" will be connected to two canisters. <br /> Purging and sample collection will proceed as described above.After collection, one sample <br /> will be labeled as the environmental sample and one as the duplicate. <br /> Equipment blanks also will be collected at each site as required in the site-specific <br /> QAPP/FSP. Generally, one blank will be collected for every ten samples collected. Blanks will <br /> be collected by running ambient air through the sampling system immediately after it has <br /> been decontaminated, and by collecting the ambient air in a Tedlar®bag, SUMMA® canister, <br /> or sorbent tube using the same procedures used to collect environmental samples. Blank <br /> sample collection is conducted "upwind" of any observed interference, and the location of <br /> the sampling must be recorded in a field logbook. Equipment blanks are collected to ensure <br /> that field equipment decontamination procedures are adequate. <br /> 2.6 LEAK CHECK PROCEDURES <br /> Leakage during sub-slab soil gas sampling may dilute samples with ambient air and produce <br /> results that underestimate the actual site concentrations or may contaminate the sample <br /> with external contaminants. A tracer gas serves as a quality assurance (QA)/QC measure to <br /> verify the integrity of the seals.Leak tests should be conducted to determine whether leakage <br /> is occurring. Leak detection is performed using the following procedures: <br /> 1. Leak tests should be conducted for every sub-slab soil gas probe. <br /> 2. Tracer compounds such as isopropanol, butane, helium, sulfur hexafluoride, or <br /> 1,1-difluoroethane may be used as leak check compounds.These compounds may <br /> be contained in common products such as Dust-Off and rubbing alcohol. Be sure <br /> the tracer compound used does not contain chemicals or impurities that may be <br /> present as a site contaminant. <br /> 3. For sub-slab soil samples, place tracer compounds around the soil gas well at the <br /> ground surface and at all connections in the aboveground sampling system train. <br /> Enrich the atmosphere in the immediate vicinity of the area where the probe <br /> intersects the ground surface with tracer gas and measure a vapor sample from <br />