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[Kansas Law Dog]

Attached is a graph of Absolute Pressure versus Altitude. At sea level the standard pressure is 14.7 psia (pounds per square inch absolute), although weather - barometric conditions cause it to vary slightly. Atlanta is the only major city east of the Rocky Mountains that is over 1000 feet above sea level, and just at 1050 feet. At that altitude the standard pressure is 14.2 psia. Hence, Atlanta is the second highest city in the NFL and Major League Baseball.

A couple more elevations / pressures are: (1) Denver at 5280 feet / 12.1 psia, (2) Ouray at 7700 feet / 11.0 psia, and (3) Imogene Pass 13,100 feet / 8.9 psia.

For those that took chemistry in high school, you may remember PV = nRT, which reduces to Vb (volume of air required per breath on top of a mountain) equals the volume of air required per breath at sea level times the pressure at sea level divided by the pressure on top of the mountain, for constant terms of nRT. Just think of it as you need to breathe an equal number of oxygen molecules whether you are at sea level or on top of a mountain.

Enough of the equations, here are the relationships:

In Denver you need to fill your lungs with 22% more air than at sea level to get the same amount of oxygen.
In Ouray you need to fill your lungs with 34% more air than at sea level.
On Imogene Pass you need to fill your lungs with 64% more air than at sea level.

Most people cannot fill there lungs with 64% more for each breath until they are fully acclimated to altitude, therefore they take more breaths per minute than at sea level. This contributes to exhaling more water vapor with each breath, which is why you need to drink more water. Also, oxygen deprivation cause a light headed feeling (or headaches). In time you will acclimate to the higher altitude. However, be sure to drink lots of water (not carbonated soda pop, beer, or wine) and pace yourself.