its only cold because its under pressure, at least im pretty sure...right? its not the gas itself that is cold, and im sure co2 cartridges are pressurized more than the n2o or whatever the nitrus molecule is, cause its gotta shoot like a hundred paintballs and shoots them pretty fast
N2O is COLD in liquid form which is what it is in the cartridge, when you pop the cartridge the N2O is no longer compressed (obviously) and changes from a liquid to a gas and is about room temperature from my experience with it.