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Section 4. Sampling with Tedlar Bags <br /> This section provides a description of Tedlar bags, <br /> practical considerations for sampling, and step-by-step <br /> instructions for collecting a grab sample. Photographs <br /> illustrate the correct way to assemble the various <br /> sampling components. <br /> 4.1 Introduction to Tedlar Bags <br /> A Tedlar bag is a container used to collect a whole air <br /> sample for landfill gas,. soil gas, and stationary source <br /> applications. The Tedlar bag is best suited for projects <br /> involving analysis of compounds in the ppmv range. <br /> AA� <br /> However, Tedlar bags can be used for other applica- <br /> tions such as ambient air monitoring for atmospheric/ <br /> fixed gases. They can be used to collect sulfur com- <br /> pounds, but only if the fittings are non-metallic (e.g., <br /> polypropylene,Teflon, or Nylon). <br /> A Tedlar bag is made of two plies of Tedlar film sealed <br /> together at the edges and features a valve that allows the interior to be filled. Sample collection <br /> requires a pressurized sampling port, a low flow rate pump, or a lung sampler. The bag expands as <br /> sample enters. When the target volume of sample is collected, the valve is closed and the Tedlar bag <br /> is returned to the laboratory. Air Toxics .Ltd. maintains a limited inventory of Tedlar bags in 1 L , 3 <br /> L, and 5 L volumes. <br /> 4.1.1 Tedlar Film <br /> Tedlar is a trade name for polyvinyl fluoride film developed by DuPont Corporation in the 1960's. <br /> This patented fluoropolymer has been used in a wide variety of applications including protective <br /> surfacing for signs, exterior wall panels, and aircraft interiors. Tedlar film is tough, yet flexible and <br /> retains its impressive mechanical properties over a wide range of temperatures (well below freezing to <br /> over 200°F). Tedlar exhibits low permeability to gases,good chemical inertness, good weathering <br /> resistance, and low off-gassing. <br /> 4.1.2 How "Active" is the Surface of a Tedlar Bag? <br /> The surface of a Tedlar bag is a work in progress. The surface of a new bag is essentially free of VOCs <br /> at the single digit ppbv level. Compounds detected from analyzing new Tedlar bags include methylene <br /> chloride,toluene, acetone, ethanol, and 2-propanol. Note that 2-propanol has been detected in some <br /> new bags up to 45 ppbv. Once the Tedlar bag is used, however, the surface has been exposed to <br /> moisture and possibly VOCs. It may irreversibly adsorb many VOCs at the low ppbv level. A series of <br /> purges with certified gas may not remove the VOCs from the surface. $15 for a new bag is a small <br /> price to pay for peace of mind. <br /> AIR TOXICS LTU. <br /> 16 <br />