Plain English Meaning

Diving underwater while breathing compressed air from a tank. After diving, the body holds extra nitrogen for hours. Flying too soon afterwards can let that nitrogen form bubbles inside the body, which can make a pilot seriously ill.

Full Definition

Underwater diving in which the diver breathes compressed air or another gas mixture from a tank carried on the body. Because the diver breathes gas at higher-than-surface pressure, nitrogen dissolves into the bloodstream and body tissues. If the diver then flies before that excess nitrogen has fully cleared, the reduced cabin or cockpit pressure at altitude can cause the nitrogen to come out of solution and form bubbles, producing decompression sickness ("the bends").

Context Anchor

Seen in pilot health and physiological factors guidance, especially in recommendations about how long to wait before flying after diving.