This happens because the temperature at which oxygen changes from a gas to a liquid is about 13 degrees Celsius above that of nitrogen. The oxygen can be seen dripping from the can just as on a humid day you can see drops of water condense and drip from a can you take from the refrigerator.
Though you technically can join the military up to age 42, if you're 35 or over you'll need an age waiver if you've never been in the military before.
Well if you want to join the Army National guard the age limit is 42, so take your age minus years your served and thats your new age ie 48 years old - 8 years in service = 40 years old... Follow.