Also, Americans have quite easy access to Nitrogen.
It is not Liquid Nitrogen, like you could be thinking, where freezing o-rings is involved.
Its better than HPA (compressed air) because it is just one gas, so more consistent.
RAILDEMON
Co2 is stored as a liquid.
In order for it to turn from a liquid, to a gas, as it does when it expands, it pulls heat from the surrounding area, so making that area cold.
It freezes o-rings, it's dirty, inconsistent and generally, past it.
HPA or Nitrogen, can be stored at a higher pressure, with greater volume, hence more shots.
Its cleaner, more consistent, doesnt freeze things (the reverse in fact)
Because it is at high pressure, when it moves through small orifices, it moves very quickly, which generates heat through friction, which is why your tank gets warm when you fill it too fast.
The heat is also a good reason why you dont mix HPA and mineral oils, which is what happened when the tank exploded.