Re: Is claim of being able to put more air at 15 psi into a vessel of 200 psi?

Air is made of Oxygen and Nitrogen molecules (mostly).  The number of 
molecules that a vessel can contain is directly proportional to how close 
the molecules can get to one another.  As the pressure increases in a 
closed system, the molecules of air the vessel can hold increases.
PV=nRT is an ideal gas law where P = pressure; V = volume; n = Number of 
moles of gas; R = gas constant; and T = temperature.
If the Volume stays the same and the temperature stays the same, the only 
variable that can increase is the number of moles.  Therefore, it is safe 
to say that at higher pressures, a vessel can contain more "air."

Jeremy B. Lynn
Engineer