Nitrogen Instead of Oxygen??

correct… "No, nitrogen does NOT have more mass. GMW of diatomic nitrogen is 28.

GMW of diatomic oxygen is 32."

volume is what i should have said … since the passing through a substrate (rubber) is limited by its size, not weight.

i think you need to revert back to V=nRT/p

I believe, Nitrogen is a more tightly packed compressed gas and therefore more stable.