This can cause destructive wear to the seal face geometry. The dimensions required are very critical. You need seal face materials that do not distort over a wide range of temperature and pressure. This can be a serious problem with most conventional seal face materials. There should be some facility available to remove any excess gas that might leak into the system.
Some consumers complain of excessive noise in the gas lines.
In some dual seal applications the barrier or buffer fluid is used to regulate the temperature at the seal faces. Gas does not do this very well because of its poor thermal conductivity. The Mc Nally Institute 1986 S. Belcher Rd.