Laws of Thermodynamic: Boyle's Law

Laws of Thermodynamic: Boyle's Law
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How Boyle’s Law Applies To A Diver’s Breathing

We will now treat of the relation between diving and Boyle’s law. We begin by once again referencing that wonderful Navy diver film, Men of Honor. In the movie Cuba Gooding’s character, in trying to persuade the medical student who later becomes his wife to tutor him, sums it up graphically: “Boyle’s Law describes the behavior of gases under varying amounts of atmospheric pressure.

It states that if a diver holds his breath at 100 feet, continues holding while rising to ten feet, then the gases in his lungs increase four times. Now why is this important to a diver? Forget to exhale on the way up, and your lungs explode (emphasis mine).” Lung explosion exaggerations notwithstanding, at the very least the diver will suffer internal injury.

When a diver is ascending, the gas or air pressure in his or her lungs is decreasing. From equation 1 in part one we can see that simultaneously, the volume of air in the lungs begins rapidly increasing. To nullify this effect, the diver must decrease this volume, and the quickest and simplest way to do this is by exhaling.

Now let us examine why this law must be considered in designing clothes and equipment for a diver.

How Boyle’s Law Applies To A Diver’s Clothes and Equipment

When a diver descends, air pressure is increasing, but its volume is decreasing. The air becomes more and more compressed. This affects the air pockets in clothing, so that the wet suit feels tighter. This effect is known as skin squeeze, and may cause physical trauma. The diver has to compensate for the lost volume by releasing air into the inflatable vest or jacket known as a Buoyancy Compensation Device (BCD).

In the descent, all of the air pockets in the diver’s body are also affected by this compression, including that in the sinuses, teeth, ear canals, mask, and even the airspace behind the ears. Divers compensate by exhaling into the mask. Conversely, as the diver ascends, he or she must get rid of the excess air by releasing it from the BCD vest. gives a basic tutorial on air pressure, with a chart on how it, the volume, and the air density changes at varying sea levels. Equipment that is designed for a diver’s use must take into consideration how all of these changing conditions may affect him or her.

Image Credits

Navy Diver from


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This post is part of the series: Thermodynamics Boyle’s Law

This series of articles describes Thermodynamics Boyle’s Law.

  1. Boyle’s Law: Part-2