Nitrogen?

[Eric_R_Kissell at whirlpool.com]

Re: Gas escaping faster

When we leak check in refrigeration, we use Helium purportedly because it
has a smaller molecule and will leak more readily through very small leaks.
Plus it is easy to differentiate from typical air, so we can use leak
detectors.  Keep in mind that in mass manufacturing we are trying to find
leaks that might cause a problem 10 years from now in several minutes of
manufacturing process time, thus the high pressure helium leak checks.
Hydrogen might leak more readily, but using a flammable gases looking for
leaks has always seemed like a bad idea.  Of course, some refrigeration
systems use flammable hydrocarbon gas as the refrigerant, but that is a
whole other conversation.

If we use the molecule size (location on the periodic table of elements) as
a decision criteria, it would appear that Oxygen (8) might leak less than
Nitrogen (7).  Note that Helium is 2 on the periodic table.

Anyway, to reduce leaking, based on the above criteria, I would suggest
that Aragon (18) is the way to go  ; -)

Food for thought,
Eric