The Carrier Gas technique measures the amount of helium leaking from part charged with Helium, into a chamber that has been swept with a carrier gas (usually Nitrogen), and vented past the mass spec unit.

This method offers measurable leak rates as low as 10^-7 std. cc/sec in high volume production applications.  This technique features a relatively high sensitivity, flexibility, and temperature and test time independency.  The method offers advantages in that it requires no roughing vacuum (lower cost and maintenance), and will therefore tolerate a much more hostile environment (slightly dirty or wet parts).  This is a relatively rugged technique.

Disadvantages include:  a higher cost than the Effect of the Leak testing methods (click above for details), time dependent, requires 2 consumables (Helium and carrier gas), chamber volume dependent, and location of the leak is not identified.  Also, part geometry may induce "blind spots," where helium could get trapped and not get circulated through the test circuit to the mass spec.

The test typically consists of the following steps:

	Establishing circulation of carrier gas around the part
	Pressurizing the part with Helium
	Monitoring Helium levels in carrier gas line

Sensitivity range [std.cc/sec]
Temperature dependence
Operator dependence
Main factors affecting sensitivity	Chamber volume
Test pressure range	any
Maintenance required	Qualified maintenance required for Mass Spec.
Cost