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Gas Laws and Scuba Diving

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on 23 November 2014

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Transcript of Gas Laws and Scuba Diving


Boyle's Law explains how the volume of a gas varies with the surrounding pressure. Many aspects of scuba diving physics become clear once you understand this simple gas law: P₁V₁=P₂V₂
Charles's Law
Risks
As scuba diving is a popular recreational sport, it should not be forgotten that scuba diving is an extreme sport with its own peculiar injuries and potentially life-threatening hazards
Barotrauma
Barotrauma is caused by the damage done by increased underwater pressure on the air pocket in the middle ear
The “bends”
Often called "the bends," decompression sickness is caused by increased underwater pressure causing the body's tissues to absorb more nitrogen
Dalton's Law
The law states that the pressure exerted by a mixture of gases is equal to the sum of the pressures which would be exerted by the gases individually (In other words, mixed gases will stay in the same proportions under pressure)
P = p₁ + p₂ + p₃ ...
Henry's Law
The mass of a gas which dissolves in a volume of liquid is proportional to the pressure of the gas: (S₁)/(P₁)=(S₂)/(P₂)
It's All About That Gas

Boyle's Law
Nitrogen Narcosis
Oxygen Toxicity
Gas Embolisms
How to avoid the dangers
Scuba Diving
By: Jenny Giacalone
Scuba diving is a form of underwater diving in which a diver uses a self contained underwater breathing apparatus to breathe underwater
The depth range applicable to scuba diving depends on the application and training, but most dives are shallower than 30m. Recreational diving limits decompression to no-stop dives or relatively short planned decompression stops to minimize risk of decompression sickness. Recreational scuba is generally limited to between 30 and 40m, depending on the group you are with
Nitrogen narcosis is a reversible alteration in consciousness that occurs while diving at depth. It is caused by the anesthetic effect of certain gases at high pressure
As a diver descends, the water pressure around him increases, causing air in his scuba equipment and body to occupy a smaller volume (compress). As he ascends, water pressure decreases, so Boyle's Law states that the air in his gear and body expand to occupy a greater volume.
To a scuba diver this assures us that our bodies absorb gases in the same proportions at any depth. It is this principle which makes it possible to estimate gas levels in our body, plan repetitive dives and avoid the bends
To a scuba diver Henry's Law tells us that at higher pressure our bodies will absorb more gasses. At great depths, the amount of nitrogen absorbed into our blood and tissue is greater than the amount absorbed at shallow depths. That is why a diver going to 100 feet has a greater risk of the "bends" than a diver who dives only 30 feet.
Most of these scuba diving dangers stem from the effects of the increased water pressure of the undersea environment, but there are also dangers posed by sea life and faulty equipment
Risks include:
-Barotrauma
-The “bends”
-Nitrogen Narcosis
-Oxygen Toxicity
-Gas Embolisms
However, a descend that is too rapid can overcome a diver's ability to equalize and result in severe pain and even injury to the middle ear
Boyle's Law contributes to the cause of this because as the pressure increases, the volume decreases, hence why air pockets form in the ear
If that pressure is suddenly reduced, this extra nitrogen forms potentially harmful bubbles. Deep divers return to the surface in carefully monitored stages, so you can control the rate at which this absorbed nitrogen is released
Henry's Law contributes to this risk because of the water pressure, body tissue absorbs nitrogen gas faster as a diver descends than when ascending to the surface. However, if a diver ascends too quickly, nitrogen gas bubbles will form in body tissue rather than being exhaled
Narcosis results in relief of anxiety – a feeling of tranquility and mastery of the environment
-Narcosis can produce tunnel vision, making it difficult to read multiple gauges
Nitrogen narcosis occurs because gases in the body behave according to Dalton's Law of partial pressures.The greater the concentration of a gas in the mixture, the greater its partial pressure
Oxygen toxicity is a concern for underwater divers, those on high concentrations of supplemental oxygen, and those undergoing hyperbaric (oxygen therapy). The result of breathing elevated partial pressures of oxygen is hyperoxia, an excess of oxygen in body tissues.
Dalton's Law contributes to oxygen toxicity. This increased oxygen level gives rise to Decompression sickness and Nitrogen Narcosis, ultimately causing blindness and unconsciousness. Oxygen Toxicity badly affects the nervous system and results in severe conditions, such as: nausea, spasm, convulsion of facial muscles, muscle twitching, and vomiting.


Gas embolism occurs when gas bubbles enter arteries or veins
Symptoms of arterial gas embolism may be present but masked by environmental effects such as hypothermia, or pain from other obvious causes; symptoms include: loss of consciousness, vertigo, convulsions, and loss of coordination
Boyle's Law contributes this. As gases get compressed their volume shrinks. As gases decompress their volume expands. Taking a 1 cubic foot balloon down in the ocean would cause it to shrink to 1/2 its size at 33 feet. Breathing at depth, ascending, and holding your breath may cause serious lung over-expansion resulting in arterial gas embolism
The risks of scuba diving are very easy to run in to. But finding ways to avoid them is not a difficult maneuver.
Make sure that all of your equipment is up-to-date on standards and regulations.
Check your oxygen rates and your pressure levels more frequently to ensure safety
Be cautious of your time spent underwater, and check your depth--you don't want to be underwater for too long
Don't be dumb and listen to your instructor, no matter how much research you did, you are NOT a professional!
The law explains why the pressure in a scuba tank recently filled may appear to drop or increase slightly depending on whether the tanks were filled outdoors, or indoors. The law also explains why scuba tanks,when being filled with compressed air, get hot
“At constant pressure, the volume of a given mass is of an ideal gas increases or decreases by the same factor as its temperature increases or decreases.”
(V₁)/(T₁)=(V₂)/(T₂)
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