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aw� <br /> to <br /> concentration data. Make sure that all equipment has been decontaminated before <br /> beginning sampling activities. <br /> A. Sampling equipment <br /> Numerous types and combinations of tubing, connectors, valves, and pumps have been <br /> used for soil vapor sampling. The tubing, gauges, and pump (if any) should be connected <br /> by tubing that is flexible, air-tight, and has a low capacity for adsorption of VOCs. <br /> Nylon tubing (marketed under the NylaFlowo name) with Y4 in OD is recommended. <br /> Teflon, Tygon®, rubber, and polyethylene tubing should be avoided. Stainless steel <br /> tubing is acceptable but has limited usefulness due to its rigidity. Swagelok® type <br /> connectors (Figure 9) should be used for all connections between tubing and other <br /> sampling components. These connectors are air-tight and reliable. Hose clamps and <br /> other types of connectors should be avoided as they may not provide an air-tight seal. <br /> The lack of an air-tight seal can allow oxygen to enter the sample, thus diluting the vapor <br /> concentrations and compromising the integrity of the sample. Leak testing (discussed <br /> below) is used to ensure the integrity of soil vapor samples. <br /> R <br /> Figure 9. Swagelok®connectors(image from equipsales.com). <br /> A vacuum must be created in order to draw the soil vapor to the land surface. The <br /> vacuum can be created by a battery powered pump, a syringe, or a sampling container <br /> that is under a vacuum (such as a Summa canister, discussed below). If a pump is used, <br /> it is important to ensure that the sample collection point is on the intake side of the pump. <br /> This will prevent any contaminants present in the pump from being drawn into the vapor <br /> sample. A three-way valve can be used to isolate the pump from a separate tube that is <br /> connected to a vapor sample container(see Figure 11). <br /> Summa canisters are strongly recommended for soil vapor samples. Tedlar® bags are <br /> not recommended. Soil vapor samples are collected in syringes in on-site soil vapor <br /> analyses only where the sample is immediately injected into a gas chromatograph(GC). <br /> A Summa canister is made of stainless steel, with a passivated, glass-lined internal <br /> surface. The passivation process utilizes electropolishing and chemical deactivation to <br /> create a chemically inert internal surface. Containers range in size from < 1 L to 15 L <br /> (Figure 10)and are provided by the analytical laboratory. Canisters are typically certified <br /> ETC Soil Vapor Sampling Technical Toolkit 15 <br /> Version 1.4, September 7,2005 <br />