Large Volume Sampling can be accomplished (e.g., at landfills, for methane, for very low detection limits
or risk assessment) using syringes and gas bulbs (250mL to 1L) or Summa canisters. Where large sampling volumes
are required, ESN uses a 10L vacuum/volume purge tank to accurately measure the volume recovered from a soil gas
hole or other sampling installation. The tank has a large gauge calibrated in volume. The tank is initially
evacuated with the 12 volt self-contained pump. Sampling devices can be put in line between the tank and the
sampling tool, such as glass bulbs, summa canisters, etc. (see figure). The valve is then opened to purge
the system and the tank gauge records the volume of gas removed. A second gauge in the sample train is used to
indicate problems with sampling in low permeability soils. This system insures that sample was actually recovered
from the test hole and that an adequate purge occurred.