What are the pressure changes in scuba diving?

Answer 1

Let's take a moment to define some terms. The typical value used to represent air pressure at sea level is 14.7 pounds per square inch or 14.7 PSIg. You can think of 14.7 pounds as the "weight" of the entire column above a one square inch surface. For convenience, this pressure is also termed one "Atmosphere" or atm. The formal definition of one atm is 1.01325 x 105 pascals. Think of one atm as "about 15 PSIg".

Unlike air, water has the property of not being compressible. The means a given volume of water "weighs" the same, regardless of depth. Accordingly, water pressure increases linearly with depth. It increases about 1/10 atm for each foot of sea water, or 1 atm every 33 feet.

A diver at 33 feet of sea water is under a total pressure of 2 atm - one atm of air and one atm of water. At 66 feet, the total pressure is 3 atm, and so on. At 660 feet, the total pressure is 21 atm (660/33) of water plus one of air).

Answer 2

The compressed air pushing against the inside of the Scuba tank causes pressure inside it.