The Discrete Interval Sampler is a stainless steel chamber attached to a reel via a length of LDPE tubing. The reel has a pressure attachment for pressurising and venting the chamber. Pressure is applied using a high-pressure hand pump.
The chamber is pressurised initially which forces a check-ball valve at the bottom downwards, preventing water from entering. When the sampler is at the desired depth, the attachment on the reel can be switched to the vent the internal pressure allowing the chamber to be filled by the hydrostatic pressure around it. At the top of the chamber there is a polypropylene check-ball that floats and closes the valve when water fills the chamber preventing sample from coming in contact with the tubing. This provides a high quality VOC sample as organic compounds will not be lost via adsorption onto the LDPE tubing.