Gas laws as they relate to divers...intellectual discussion

[firemanjoe]

I am putting a class together for the guys at work regarding dive physiology. Main topic of discussion is how pressure affects divers. I am referring to Dalton's Law, Boyle's Law, Charles' Law and Gay-Lussac's Law.

Dalton's Law states that the total pressure exerted by a mixture of gases is equal to the partial pressures of each gas in the mixture.

Boyle's Law states that the volume of a gas changes inversely with the pressure of the gas as long as no temperature changes or amount of gas has been made.

Charles' Law states that the volume of a gas is directly related to the temperature when there is no change in pressure or amount of gas.

Gay-Lussac's Law says that the pressure of a gas is directly related to its temperature in Kelvin.

Question is this-
How do these laws affect divers? These are in every dive book we have at the station but little mention as to how they work for divers.

thanks

 

[*dave*]

I am putting a class together for the guys at work regarding dive physiology. Main topic of discussion is how pressure affects divers. I am referring to Dalton's Law, Boyle's Law, Charles' Law and Gay-Lussac's Law.

Dalton's Law states that the total pressure exerted by a mixture of gases is equal to the partial pressures of each gas in the mixture.

Boyle's Law states that the volume of a gas changes inversely with the pressure of the gas as long as no temperature changes or amount of gas has been made.

Charles' Law states that the volume of a gas is directly related to the temperature when there is no change in pressure or amount of gas.

Gay-Lussac's Law says that the pressure of a gas is directly related to its temperature in Kelvin.

Question is this-
How do these laws affect divers? These are in every dive book we have at the station but little mention as to how they work for divers.

thanks

Dalton's Law is at the heart of deco theory, narcosis and O2 toxicity

Charles' Law is most obvious in dealing with tank pressure and explains why hot fills or leaving a full cylinder in the car trunk on a hot Summer day are bad.

Boyle's Law is all about pressure's impact on gas spaces. Buoyancy, over expansion injuries and Archimedes Principle are all tied to this law.

Gay-Lussac's Law... Crap, this is the first I recall hearing of this one. It seems to step on Charles... What OW manual teaches this law?

 

[Walter]

Dalton's Law along with Henry's Law affect divers with respect to decompression theory.

Boyle's Law affects divers with respect to buoyancy and avoiding barotrauma - squeezes and over expansion injuries.

Charles' Law affects hot air ballons, but has no application to diving.

You are confusing Gay-Lussac with Amonton who predated Gay-Lussac by over a century. Amonton's Law affects divers with respect to filling tanks and having tanks exposed to high temps.

Charles' Law is most obvious in dealing with tank pressure and explains why hot fills or leaving a full cylinder in the car trunk on a hot Summer day are bad.

Nope. Charles' Law deals with temperature and volume, not pressure.

Gay-Lussac's Law deals with combining volumes. There's no diving application, but people sometimes think he developed the law dealing with temperature/volume or sometimes temperature/pressure relationships.

 

[*dave*]

Charles' Law affects hot air ballons, but has no application to diving.

Next time you get a hot fill and splash with less than working pressure, what law would you use to explain the drop in pressure?

 

[Teamcasa]

Nope. Charles' Law deals with temperature and volume, not pressure.

An expanding gas in a confined space is still explained by Charles's Law.

 

[*dave*]

Yep, you are correct... The Ideal Gas Law combines Boyle's and Charles' law to tie pressure, volume and temperature together.

wow, thanks for making that point.

Nope. Charles' Law deals with temperature and volume, not pressure.

Gay-Lussac's Law deals with combining volumes. There's no diving application, but people sometimes think he developed the law dealing with temperature/volume or sometimes temperature/pressure relationships.

 

[*dave*]

An expanding gas in a confined space is still explained by Charles's Law.

Gas can't expand in a confined space, which is why pressure increases. I know you know, but.....

 

[Walter]

Next time you get a hot fill and splash with less than working pressure, what law would you use to explain the drop in pressure?

That would be Amonton's Law, Dave.

An expanding gas in a confined space is still explained by Charles's Law.

A gas in a rigid container cannot expand. Pressure will increase, but not the volume. This describes a SCUBA cylinder and was worked out by Amonton long before Charles developed his law. If the gas is in a flexible container, the volume will increase. This describes hot air balloons and was worked out by Charles.

 

[Teamcasa]

You are right, I do know. However, (in light of the OP's question, How do these laws affect divers?) the picture is easily painted by explaining just what happens to a gas when it is heated, in a confined space, like a SCUBA tank.

I would have gone to a Diesel/Gasoline engine but since this is SCUBA, it not relevant except for how a compressor works.

 

[*dave*]

yanno... I've been using Charles' to explain hot fills and pressure drop in cold water for a few years now. While I was getting the concept across, I was using the wrong law. Kinda embarrassing, but it's more important I clean up my act.

You are right, I do know. However, (in light of the OP's question, How do these laws affect divers?) the picture is easily painted by explaining just what happens to a gas when it is heated, in a confined space, like a SCUBA tank.

I would have gone to a Diesel/Gasoline engine but since this is SCUBA, it not relevant except for how a compressor works.