Nitrogen narcosis, also called "rapture of the deep," is a condition that occurs in divers breathing compressed air from a tank. The condition becomes noticeable when divers go below about 100 ft. At that point, they experience an altered mental state similar to alcohol intoxication. Nitrogen narcosis has also been called "the martini effect" because for every 50 ft of depth beyond the initial 100 ft, the effect is something like drinking one martini on an empty stomach. At 300 ft, the effect becomes disabling, causing stupor, blindness, unconsciousness, and even death.

Nitrogen narcosis occurs because gases in the body behave according to Dalton's Law of partial pressures. The law states that the total pressure of a gas mixture is equal to the sum of the partial pressures of gases in the mixture. Partial pressure is the pressure exerted by any one of the gases in the mixture. The greater...