NAUI Nitrox Diver
10 Introduction
Technical divers will breathe a highly oxygen-rich
nitrox mixture during their shallower decompression
stops or long exposures in the shallow zones in order to
more efficiently eliminate nitrogen from their bodies.
Another very common use of nitrox in diving is
simply as a safety margin. Divers who choose to dive
conservatively will often breathe nitrox but continue to
use air dive tables or an air computer. Over a series of
dives, they will absorb significantly less nitrogen than
their tables or computers indicate, effectively lowering
their risk of decompression sickness.
Finally, there may be truth in the claim of divers
that they are less physically tired after a series of dives
on enriched air nitrox. With less nitrogen in their bodies
than they would have had diving on air, the divers may
indeed feel less fatigue at the end of their diving day or
diving trip.
COMMON MISCONCEPTIONS ABOUT NITROX
As was said earlier, many misunderstandings developed
about nitrox as it began to be known (but not well
understood) in the recreational diving industry. Before
you move on to the next topic in this course, you should
be aware of some of the persistent myths about nitrox
and be able to sift the fact from the fiction.
Myth 1: “Nitrox is for technical diving.”
Although technical divers use oxygen-enriched air
when appropriate, such as during in-water decompression
stops, the use of nitrox does not make a dive “technical.”
Technical dives are planned decompression
dives, deep dives where both nitrogen and oxygen in the
breathing gas may be diluted with helium (trimix),
dives in which one changes between gas mixes during
the dive, dives that use an oxygen percentage greater
than 40%, or dives into overhead environments such as
caves or wrecks.
Myth 2: “Nitrox is for deep diving.”
Quite the opposite. Because of the increased concentration
of oxygen in nitrox, there are stringent depth limits
imposed to prevent oxygen toxicity. Nitrox is a mid-range
breathing gas and provides the greatest advantages for
dives in the 15- to 33-meter (50- to 110-foot) depth
range. Beyond that depth the decompression advantage
gain is minimal, and the risk of oxygen toxicity problems
increases rapidly. Later in this book you will learn how to
determine maximum operating depth (MOD) for various
nitrox mixes.
Myth 3: “If you dive with nitrox you won’t get
bent.”
Enriched air nitrox only reduces the fraction of
nitrogen in the gas you breathe; it does not eliminate it.
Moreover, no breathing gas mixture, dive table, or dive
computer can absolutely eliminate the possibility of
decompression sickness. Nitrox has advantages over air
because the partial pressure of the nitrogen is less for
any given depth. Nitrogen accumulation is slower, but
you must still monitor depth and time–as well as the
specifics of your breathing mixture–to avoid excessive
nitrogen accumulation in your body. The knowledge
and procedures in this text will help you control the
risks of decompression sickness while maximizing the
safety and enjoyment of your dives.
Myth 4: “Nitrox is safer than air.”
Nothing that we do is entirely without risk. All
diving involves some risk, and as noted above, there
are risks associated with nitrox. In this course, you
will learn procedures and techniques to responsibly
manage and minimize the risks of using oxygenenriched
air. Nitrox has advantages over air in many
diving applications, such as increased available dive
time and decompression advantages, but with these
advantages comes your added responsibility to be
mindful of oxygen levels and depth and time limits,
analyze you own gas mixture, properly maintain your
equipment, and dive prudently.