Services | Discrete Vadose Zone Sampling

Discrete Vadose Zone Vapor Sampling Devices
The Post-Run Tubing System (PRT)

The Post-Run Tubing System (PRT) is the most common way to recover vapor samples. The PRT system consist of O-ring connections that enable the PRT system to deliver a vacuum-tight seal to prevent sample contamination from up hole. With the PRT system the sample can be drawn through the point holder, adapter and into the sample tubing via a vacuum pump.

Sampling Purge Volumes
1 Volume = Volume of polytube 4.4647ML/ft
pointholder & 3" of rod pull back= 60ml

Volume Purge/ML
5'depth
10'depth
15'depth
20'depth
25'depth
30'depth
35'depth
40'depth
Volume
82.32ml
104.65ml
126.97ml
149.29ml
171.62ml
193.94ml
216.26ml
238.59ml
Purge Volume 200cc/min
24.7 sec
31.4 sec
38.1 sec
44.8 sec
51.5 sec
58.2 sec
64.9 sec
71.6 sec


V= Volume
Tubing 0.25 in OD, 0.17in
H=Depth
r=Radius


Derived from fomula



Note: Please keep in mind that not every soil yields soil gas. Some damp to moist, fine grated, well compacted plastic clays (which have been slightly compressed by probe rod insertion) will not yield soil gas to the tool string no matter how much vacuum is applied. The solution to this problem consists of applying a vacuum and shutting off the line valve and slowly retracting the probe rods until the tip passes through a permeable zone. Soil gas will enter the system and the gauge on the vacuum source will respond abruptly.





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