What is residual nitrogen?

Residual nitrogen refers to the nitrogen that remains in a diver's body after surfacing from a dive, which is dissolved in blood and tissues due to the pressures experienced underwater. When divers descend and ascend, the pressure changes can cause nitrogen present in the body to be absorbed and released. During a dive, especially at greater depths, increased pressure allows more nitrogen to dissolve into bodily fluids. Upon surfacing, this nitrogen does not immediately leave the body; instead, it remains in the bloodstream and tissues until the diver's body gradually expels it over time through normal respiration and other physiological processes.

Understanding residual nitrogen is crucial for divers as it relates directly to the risk of decompression sickness, often referred to as "the bends." Managing and monitoring residual nitrogen levels is essential for ensuring safe diving practices and determining dive schedules, notably the need for safety stops or surface intervals between dives.

The other options relate to different concepts concerning nitrogen and diving: some focus on nitrogen consumption or exhalation, but none correctly define the specific leftover nitrogen in the body post-dive as residual nitrogen does.