I want to add a gas cylinder for my air horns instead of having to buy a air compressor. I want to use a nitrogen or compressed air welding cylinder but my question is,if I use the same size tank (55cf) which has more product?Nitrogen or compressed air? I have read other post that most use Nitrogen why is that? I am using a 55cf tank so it will fit in my tool box. I will need a GOOD regulator also I need someone to give me some advice on a good one to use for this type of thing. Thanks