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Chapter 1 Introduction 17
from a depth of 74 meters (243 feet) in 1939. Because
of the expense and rarity of helium, heliox remained
limited to military diving applications until it entered the
commercial sphere some time later.
Nitrogen-oxygen mixtures other than air have a
history extending back more than half a century (Figure
1-2). Although the role of nitrogen in decompression
sickness had long been recognized, it was not until
1935 that A.R. Behnke and others first attributed the
debilitating narcosis that occurred during deep air dives
to the increased partial pressure of nitrogen. In the
early 1940s, Dr. Christian Lambertsen, working for the
U.S. Navy, proposed that various mixtures of nitrogen,
helium, and oxygen could be used to limit problems of
both oxygen toxicity and decompression sickness. In the
1950s, Dr. Ed Lanphier conducted extensive research
for the Navy on nitrogen-oxygen mixtures. Lanphier
was also largely responsible for the 1959 Navy Diving
Manual in which the use of oxygen-enriched air made its
appearance.
The first use of oxygen-enriched air for commercial
diving is believed to be by Andre Galerne of International
Underwater Contractors. In the late 1950s, Galerne
developed a protocol using EAN50 that permitted his
divers to greatly extend their available working time at
moderate depths of about 20 meters (65 feet). Galerne’s
method used the concept of equivalent air depth, which
is based on the knowledge that reduced partial pressures
of nitrogen allow the use of considerably shallower-thanactual
dive table depths in planning and executing dives.
As this gave him considerable commercial advantage,
Galerne kept his techniques largely to himself.
Credit for developing and introducing nitrox diving
techniques for standard scuba goes to Dr. Morgan Wells.
As the first Director of the NOAA Diving Program, Wells
began experimenting with the use of nitrogen-oxygen
mixtures in about 1970. Using “equivalent air depth,”
the NOAA Diving Program began utilizing nitrox on
diving projects in about 1975. A 32% oxygen mixture for
NOAA divers was settled upon as a standard. The second
edition of the NOAA Diving Manual, which appeared
in December 1979, published the results, calling the
32% mix NOAA Nitrox I and including a set of NOAA
Nitrox I dive tables that allowed the scuba diver to plan
nitrox dives. Several methods for mixing nitrox were
also published. For common diving ranges, the diver, in
effect, was allowed to use a depth on the NOAA Nitrox I
dive tables that was one 10-foot increment shallower than
the actual standard air dive profile. At the same time as
NOAA Nitrox I was making its appearance, Wells and the
NOAA Diving Program were using equivalent air depth
calculations to develop additional protocols for other
nitrox blends. EAN36 soon became known among nitrox
users as NOAA Nitrox II, although it was not until 2001
that the NOAA Diving Manual (fourth edition) finally
published it as an “official” mix and included appropriate
NAUI developed and designed dive tables (Figure 1-5).
In 1985, Dick Rutkowski, who had served as
Deputy Diving Coordinator under Morgan Wells and
helped to develop the oxygen-enriched air techniques,
retired from NOAA. Upon his retirement, Rutkowski
founded Hyperbarics International and the International
Association of Nitrox Divers to make available courses
for recreational divers and teach them the NOAA nitrox
diving techniques. Awareness of Rutkowki’s nitrox course
grew slowly but steadily, and over the next few years a
growing, but largely disregarded group of recreational
nitrox divers appeared.
Figure 1-3 Nitrox is used both commercially and
recreationally around the world.
Figure 1-4 As a diver, you need a certain amount
of knowledge, awareness, caution and
sensibility to use nitrox safely.