Hmm, thanks for the interesting info. That kind of makes sense; maybe pure CO2 escapes through the pores in your tubes more easily than the mixture of gases in the air? Although air is mostly nitrogen, if I recall correctly, and that's N2. Wouldn't that molecule be smaller even than CO2 and thus even more prone to seep out? That makes me wonder what the composition (%) of air in our tubes is, and if over time it ends up with different gas ratios than the air around us. Chemistry nerds on TE, help!

Anyway I'm not a CO2 cartridge fan anyway. Every time I try to use one, it blows up or doesn't work or something. I'm going back to a good ol' hand pump as soon as I get my new bike.