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.04 <br /> VACUUM <br /> GUAGE TUBING <br /> 200 ml/min <br /> FLOW CONTROL <br /> ORIFICE <br /> PURGE <br /> PUMP <br /> SUMMA <br /> CANNISTER <br /> SOIL VAPOR <br /> SAMPLING POIN <br /> Figure 11. Equipment arrangement for soil vapor purging and sampling (by Chuck <br /> Zuspan, CVX ETC) <br /> The exact procedure used in obtaining a soil vapor sample will vary as a function of the <br /> equipment used. There are however a number of topics which are consistent across <br /> equipment types. <br /> 1. Sample containers <br /> A number of sampling containers have been used for soil vapor sample collection, <br /> including Summa canisters, Tedlar® bags, Cali-5-Bond® bags, syringes, and sorbent <br /> sampling tubes. We highly recommend Summa®canisters,which are stainless steel, gas- <br /> tight, opaque, and laboratory-certified clean (see Section A Sampling Equipment above). <br /> The canister is evacuated by the lab to a pressure of -29.9 in Hg. 100 % certified <br /> canisters (1 L for sub-slab samples) are required for soil vapor analysis using the <br /> recommended analytical method, EPA Method TO-15 (described below). <br /> 2. Vacuum/flow rate and flow regulator/particulate filter <br /> The vacuum and resulting sampling flow rate should be minimized in order to limit <br /> enhanced volatilization of VOCs from water and sediment into the soil vapor sample. <br /> Using a low vacuum and low flow rate will aid in obtaining a representative soil vapor <br /> sample and also reduce the possibility of leakage of ambient air into the sampling <br /> equipment. Consistency in vacuum and sample flow rates should be maintained between <br /> ETC Soil Vapor Sampling Technical Toolkit 20 <br /> Version 1.4, September 7,2005 <br />