rebreathers that re-circulated pure oxygen while removing
carbon dioxide. Seemingly, the seriousness of the
hyperbaric oxygen problems in diving was not fully
appreciated until a number of oxygen-toxicity accidents
among military divers early in World War II.
As early as 1919, it was suggested that nitrogen
could be replaced by helium to increase divers’ operational
working depth. Work on helium-oxygen mixtures
began in earnest in the 1930s. In 1937, Max Gene Nohl,
breathing a helium-oxygen mixture and using a suit of
his own design, dove to a depth of 128 meters (420 feet)
in Lake Michigan. The first practical test of heliox was
the U.S. Navy’s salvage of the submarine USS Squalus
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.
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 was probably 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
than-actual dive table depths in planning and
executing dives. As this gave him considerable commercial
advantage, Galerne kept his techniques largely to
himself.
NAUI Nitrox Diver
6 Introduction
1878 Paul Bert shows nitrogen to be cause of
DCS.
1908 J. S. Haldane publishes first diving
decompression tables.
1935 Behnke et al. attribute narcosis to nitrogen.
1937 Gene Nohl dives to 420 feet on heliox.
1939 US Navy uses heliox for USS Squalus
salvage.
1940 Lambertsen proposes N2, O2, He mixtures.
1950sAndre Galerne using nitrox in commercial
diving.
1959 U.S. Navy Diving Manual introduces
oxygen-enriched air.
1975 Morgan Wells using nitrox with NOAA
divers.
1979 NOAA Diving Manual publishes NOAA
Nitrox I as standard mix.
1985 IAND formed–Rutkowski expands nitrox to
recreational diving.
1988 Harbor Branch Workshop on EANx Diving.
1991 Nitrox training agencies almost barred
from DEMA Show.
1992 aquaCorps/SDRG pre-DEMA Workshop.
1992 NAUI sanctions teaching enriched air
nitrox.
1994 Rodale’s Scuba Diving supports nitrox
training.
1995 Other recreational training agencies accept
nitrox.
1996 NAUI publishes Enriched Air Nitrox Diver
standards.
1997 NAUI publishes its first nitrox textbook.
1999 Reduced Gradient Bubble Model
introduced.
2001 NAUI RGBM Nitrox Dive Tables published.
FIGURE 1-2: TIMELINE OF THE GROWING KNOWLEDGE AND
ACCEPTANCE OF ENRICHED AIR NITROX