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our mobile laboratory has been field tested for ruggedness and dependability in <br />extreme and diverse environments. <br />Field Products <br />Passive Diffusion Bag (PDB) Samplers for the Collection of Groundwater Samples <br />for Volatile Organics Analysis <br />CAS has been granted a license to manufacture, use and provide the bags by the <br />US Geological Survey (USGS) and The General Electric Company (GE), both co - <br />patent holders on the product (US #5,804,743). The downhole passive water <br />sampler and method of sampling was invented by Don Vroblesky (USGS) and <br />Thomas Hyde (GE). <br />PDB Samplers are made of low-density polyethylene (LDPE), which acts as a <br />semipermeable membrane. Volatile Organic Compounds (VOC's), excluding certain <br />ketones, ethers and alcohols diffuse readily through the membrane. An equilibrium <br />is established between the VOCs in the bag and those in the groundwater. The <br />PDB Sampler, in the shape of a long cylindrical tube, is filled with analyte -free water. <br />It's available in both field -ready and field -filled versions. It is simple to deploy, <br />eliminates the collection and disposal of purged water and significantly reduces the <br />cost of sampling. Upon retrieval, usually 14 days after deployment, bags are opened <br />to fill vials and returned to the laboratory for analysis. <br />Page 21 of 29 <br />