Small Diameter Passive Diffusion Bag Samplers (PDBs) are used in place of purging and low-flow sampling methods in groundwater monitoring wells less than 2-inches diameter to obtain representative, discrete interval samples of Volatile Organic Compounds under natural groundwater flow conditions. Because these samplers are smaller in diameter than our Equilibrator for 2-inch wells, they are longer in length to obtain sufficient sample volume for analysis.

The PDBs are installed in the saturated screen zone where natural groundwater flow refreshes the water in contact with the samplers. VOC molecules enter and exit the sampler’s semi-permeable membrane based on the concentration gradient between the well water and the sampler, maintaining a dynamic concentration equilibrium. After sufficient deployment time the PDBs are removed and the contents emptied into VOA bottles using a “juice box straw” emptying device.

To install Small Diameter Passive Diffusion Bag Samplers (PDBs) the following basic, re-usable, installation materials are recommended;

  • Suspension Tether to which the samplers are attached and suspended in the well,
  • Re-usable Stainless Steel weight to pull the tether assembly into place in the well,
  • A well cap from which to hang the suspension tether,
  • Connectors located on the tether at the location where the sampler is to be deployed and to which the samplers are connected using zip ties.
  • A small reel is helpful for raising or lower the assembly into the well without tangling.

EON’s Small Diameter PDBs are supplied pre-filled with de-ionized water, ready for installation and are designed to be extremely easy to install and rugged to survive unexpected field events.