What is Charles law in regards to scuba diving?

Answer 1

Charles' Law states that the volume of a constant amount of gas (i.e. moles) held at a constant pressure will vary in volume directly with absolute temperature. As far as this pertains to Scuba. hot air takes up more "room" in your tank. So when your tank is filled, the gas volume becomes denser, pressure increases, and so does the gas temperature. So a newly filled tank 80cu ft tank may show a temperature of 120F and a pressure of 3000psi (so theoretically this tank contains 80cu ft of air at 3000psi; the fill pressure). Later, if the tank cools down, the gas inside the tank also chills and condenses, causing a pressure drop. Thus, the tank in the example will contain less are (and cool, less pressure) than a tank that remained cooler on filling. A second, more important application relates to The Bends, or Nitrogen supersaturation. As you dive on compressed air at pressures over surface pressure (1 atm). Nitrogen (and other gases) dissolve in your tissues. The more pressure over time, the more gas dissolves in your system. Ideally, you'll spend your dive in such a way that, as you depressurize (ascend), the dissolved gases that are now soming out of your tissues will be expelled as gases in the lungs, and you'll simply outgas them by breathing. Problems arise, however, when the gas comes out of solution so quickly and in such volume that instead of being transported to the lungs and outgassed, it forms bubbles within the tissue. Depending on the size and quantity of bubbles, and where they form, this problem can range from being asymptomatic or presenting as an itch, all the way up to occluding major bl;ood vessels resulting in mini-strokes and even death (although death from the Bends is very rare, and this condition can be treated before fatality in most instances). Charles' law comes in when a diver who is very near to being bent or is only slightly symptomatic boats. At that point, warming the diver may invoke Charles' law and increase the size of any existing bubbles, thus doing more tissue damage. The first responder to a diver with the bends, then, is confronted by a difficult decision: warm the diver and prevent hypothermia but increase the damage caused by the bends, or don't warm the diver, and risk hypothermia.