Air question

[susandennis]

When you buy canned air and then you use up all the air, it still blows.  You don't get that wet cold stuff but you get air coming out which is, honestly, all I feel I can ask out of a can of air. So, why would you ever need a new one?  What's the magic to that wet cold stuff? 

How redundant would it be to mention that I dropped out of chemistry when half of my 23 unknowns evaporated before I could get to them?  And I just flat failed physics.  Somehow I think one or both of those disciplines would have helped me understand why my empty can of air is still giving me a decent blow job and why I should not think it's decent and should go buy a new one.

Seriously.  Really.