How are gases separated for bottling?

Dave - So this is how you separate oxygen from nitrogen in the air or helium. The way that it's done commercially is by cooling air down and all the different gases in air have different points at which they condense so carbon dioxide will come out first, then oxygen, nitrogen and argon. If you slowly cool it down at different temperatures you take out different gases, different liquid gases. Helium isn't found in the atmosphere. You can only find it in the top of oil wells. It's caused by radioactive decay.