Making soil collars for the LI-8250, Smart Chamber, and other soil chambers

Follow these guidelines if you want to make your own soil collars. If you construct a collar from a material with a different inside diameter than that of LI-COR soil collars, be sure to recompute the chamber volume and use the new volume in flux calculations.

20 cm collars (LI-8250, Smart Chamber, LI-8100A, and LI-6800)

Modern LI-COR soil gas flux systems use 20 cm soil collars.

You can make your own collars if you can acquire suitable pipe. Large soil collars from LI-COR are constructed from thick-walled, 8-inch SDR 35 PVC pipe. This material is widely available in the United States. In other countries, you may need to special order the PVC pipe or find a similar alternative.

To construct a collar, cut a length of pipe to approximately 11.43 cm. Then, use a grinder or coarse file to bevel the bottom edge to a 24° angle. The bevel is optional but does allow for easier insertion of the collar into the soil.

• Inside Diameter: 20.1 cm ± 0.03 cm
• Outside Diameter: 21.34 cm
• Height: 11.43 cm

10 cm collars (LI-8100A and LI-6400/XT)

Older soil gas flux systems are compatible with the 10 cm collar.

The 10 cm (4 inch) collars are made from thin-walled polyvinyl chloride (PVC) sewer pipe. The pipe must have an inside diameter of 10 cm (3.930 inches) minimum and an outside diameter of 11.4 cm (4.5 inches) maximum. Cut a section approximately 8.9 cm (3.5 inches) or longer, depending on requirements for your measurement. Bevel the bottom edge with a grinder or coarse file.