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Hyperventilation An increase in rate and/or volume of breathing. Carbon
dioxide blood levels decrease with little corresponding
increase in oxygen blood levels. If the diver engages in
excessive hyperventilation, he may diminish his desire to
breathe, long enough to become unconscious after a long
period of apnea.
Hypoxia A condition that occurs when a diver’s tissues do not
receive enough oxygen. Freedivers become hypoxic when
they hold their breath; they can eventually suffer blackout
if they hold their breath too long.
Multi-level dive A dive that includes time spent at various depths and whose
no-decompression limits are therefore not determined
solely by the maximum depth attained.
NITROX In sports diving refers to any mix with a higher fraction of
oxygen than standard air.
NOAA United States National Oceanic and Atmospheric
Administration.
No-decompression time
The maximum amount of time a diver may remain at a
particular depth without having to make decompression
stops during the subsequent ascent.
