How to Understand Underwater Pressure in Scuba Diving
Almost all diving techniques and knowledge center around the principle of pressure. Here are a few basic concepts you should master.
- Difficulty:
- Challenging
Instructions
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1
Know that air pressure decreases with altitude and water pressure increases with depth.
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2
Understand that, because water is denser than air, pressure increases more rapidly as you descend.
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3
Know that the human body is mostly water, and that in recreational diving, water pressure will be felt in the air spaces of the body (lungs, sinuses and ear canals).
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4
Understand the meaning of 'atmosphere of pressure.' The air pressure at sea level is defined as one atmosphere of pressure (1 ATM).
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5
Know that pressure increases at the rate of 1 ATM every 33 feet of water depth. A diver at 33 feet of depth is at 2 ATM, 3 ATM at 66 feet, and so on.
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6
Understand that air volume in a flexible space (such as your lungs and sinuses) is reduced proportionate to pressure. At 2 ATM the volume is halved, at 3 ATM it is a third of surface volume, and so on.
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7
Know that air density (such as in your lungs and scuba tank) is proportionate to pressure. At 2 ATM the density is doubled, at 3 ATM it is tripled.
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8
Realize that air within an air space will expand proportionally as pressure is reduced. For example, moving from 2 ATM to 1 ATM (33 feet underwater to the surface), air in a closed container will double. Keep this in mind when surfacing.
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Tips & Warnings
Understanding these concepts shows how important it is to ascend slowly while scuba diving. It's extremely dangerous for air to expand too rapidly inside your lungs.
