Plain English Meaning

Gases the body absorbs but doesn't use. Nitrogen is the main one. It rides along in your blood and tissues without doing anything — until the pressure around you drops fast enough that it bubbles out, which is what causes the bends.

Full Definition

Gases that do not chemically react with body tissues and are simply dissolved in the blood and tissues under pressure. In aviation physiology, the inert gas of concern is nitrogen, which makes up about 78 percent of the air a pilot breathes. When ambient pressure drops rapidly, dissolved nitrogen can come out of solution and form bubbles, causing decompression sickness.

Context Anchor

Seen in discussions of altitude-induced decompression sickness, especially after scuba diving or during high-altitude flight without proper pressure protection.