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54 NAUI Nitrox Diver
appropriate FO2 and planned depth. For example, the
best mix at a PO2 of 1.4 ata for a dive to 28 meters (92
feet) is 36% O2. When diving with oxygen-enriched air,
it is essential that you know the maximum operating
depth for the gas with which you are diving. The MOD
should be determined for each cylinder independently
at the time the contents are analyzed (see Chapter 7). It
should be marked clearly on the cylinder contents label,
and the cylinder should be checked before the dive. Best
mix allows you to have more control over your diving by
using the optimal nitrox blend for your dives, perhaps
gaining additional no-required-decompression dive time
in the process.
Planning and executing a nitrox dive requires more
than just knowing the maximum operating depth or the
nitrox blend you will use. When you dive, you must also
plan your dive time. In the next chapter we will present
dive tables and dive computers as they are used in
enriched air nitrox diving.
Verify What You Have Learned
Review the following questions about
Choosing the Best Nitrox Mix:
1. What are the two standard nitrox mixes?
2. What is Maximum Operating Depth?
3. Using the Maximum Operating Depth table, what
is the MOD for EAN36 if the PO2 is not to exceed
1.4 ata?
4. What is the first thing you need to find when
calculating the maximum operating depth for any
nitrox mixture?
5. What is the range of oxygen percentages you can
set on the NAUI MobileTM App calculators?
6. What is Best Mix?
7. Using the Oxygen Percentages for Best Mix table,
what is the best mix for a 30 msw (100 fsw) dive
with maximum PO2 of 1.4 ata?
8. Explain how to calculate best mix.
For answers, see Appendix.
Pioneers Paving the Way
Throughout diving’s history, it is NAUI leaders,
pioneers and trend setters who have defined the
sport. Whether in the establishment of scuba
instructional standards, equipment development,
advancements in underwater research or dive
training innovations, NAUI pioneers have paved
the way for divers around the world.
Tom Mount (1939-present)
Tom Mount is a technical diver and cave diver.
In 1991, Mount joined Dick Rutkowski in the
International Association of Nitrox and Technical
Divers (IANTD) to teach Nitrox to recreational
divers. In 1992, Mount was named president
and chief executive officer of IANTD, a position
that he held until 2005. Mount was one of
the pioneers in relation to diver training and
development of dive tables in relation to the use
of trimix as a breathing gas for diving. Also a
founding member of the National Association for
Cave Diving, Mount has taken a leading role in
the development of closed-circuit rebreathers
for recreational diving. Mount has worked for
the Army Core of Engineers, NOAA, Teach Tour
Dive Travel Company and the YMCA as training
director. From 1965 to 1967, he jointly held
the world record for the deepest dive made on
compressed air.
Mount has published numerous technical
diving texts, including the Technical Diver
Encyclopedia, Exploration and Mixed Gas
Diving Encyclopedia, and Tek Closed Circuit
Rebreather. In 2000, his contributions to
recreational scuba diving were acknowledged
by the Academy of Underwater Arts and
Sciences with a NOGI Award for “Sports/
Education." He has received Beneath the Sea’s
Diver of the Year award; Rebreather Worlds
Life Time Achievement Award, TEKDiveUSA;
DEMA’s Life Time Achievement Award and
numerous other recognitions from various diving
associations as well as the NOAA.