by: Jakob Jelling
Dalton's law refers to the effects which partial pressure might have on divers. This law says that the pressure of mixed gases is equal to the pressure produced by the individual gas. It can also be explained by saying that the total pressure of a mixture of gases equals the sum of the partial pressures of gases which are part of it.
This means that the number of molecules present in the total volume of a gas is proportional to the number of molecules present on each one of the gases which compose it. This way, while the total gas pressure increases as a diver goes deeper into the water, the partial pressure of each gas involved increases as well, and the effects which might cause on the divers body also increases with it.
For example, air is a mixture of gases which contains about 80% of nitrogen and 20% of oxygen although it also includes small amounts of other gases as well. According to Dalton's law, the partial pressure exerted by the nitrogen and by the oxygen which make the air will be equal to the total pressure of the air; and they will increase simultaneously.
A specific case in which the effects specified by Dalton's law should be seriously considered by divers is regarding nitrogen. Whenever there is an increase of the partial pressure of nitrogen, this would cause a higher nitrogen concentration dissolved in the diver's blood, and this could cause him to suffer a nitrogen narcosis. This, among many other situations which might arise due to the facts stated by Dalton’s law, should be prevented by a proper planning of the diving activities which a diver intends to practice.
The effects which a gas might cause on a diver are based on the pressure which such gas exerts on his body. This explains why Dalton's law is so important for divers and why they should understand it and prevent the effects it explains. Partial pressure related problems can affect the human body in several ways, such as causing nitrogen narcosis or ear canal damage among others, and therefore divers should pay attention to these dangers and take the necessary precautions.