who has cannisters of nitrogen though? CO2 all the way, and CO2 is bigger than air, but it still leaks out quicker than air 'cos it disolves in latex (disolves in butyl too which is why the normal butyl tubes are down the next day after a quick repair too)
(I’m not completely sure disolves is the right chemistry like effect between a gas and a solid here, but it’s getting out more analgous to that than because of any tiny holes in the latex)