Oxygen Enriched Air: A New Breathing Mix?
Larry "Harris" Taylor, Ph.D.
This is an
electronic reprint based on the article that appeared in IANTD Journal (Sept/Oct
1993). This material is copyrighted and all rights retained by the author. This
article is made available as a service to the diving community by the author and
may be distributed for any non-commercial or Not-For-Profit
All rights Reserved.
This is the oxygen-enriched air section of my article
the history of mixed gas
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The first preparation of oxygen was by the English chemist
Joseph Priestly in 1773. Shortly thereafter, the French chemist, Antoine
Lavoisior determined that oxygen was vital to life. Lavoisior named the gas
"oxygen" (means "acid former" because he incorrectly believed this new gas to be
the essence of acids). By 1794, the English physician Reddoes had established
breathing oxygen- enriched air as a medical procedure. Paul Bert published the
results of some 670 experiments with oxygen-enriched atmospheres using a
hyperbaric chamber in 1878. Earlier, in 1874, Bert furnished balloonists with
bags containing 40 and 70% O2 so that they could survive the hypoxia
associated with their balloon ascensions. Bert was also the first to propose
that CNS oxygen toxicity was a function of the oxygen
Fleuss, Master Diver for Siebe, Gorman & Co. of
London, conducted the first documented dive using oxygen-rich air. Breathing an
estimated 50-60% O2, Mr Fleuss spent an hour in a large tank. A week
later, he used his apparatus in open water. He was injured when tenders on the
dive abruptly pulled him to the surface. The dives were conducted in 1879. By
1912 Robert Davis and Leonard Hill had devised a self-contained rigid diving
helmet that utilized a 50% oxygen-nitrogen mixture. This apparatus was used
under the guidance of J.S. Haldane to a working limit of 100 fsw. Since the
nitrogen concentration was much less than air, this device demonstrated the
then-remarkable decompression advantage available from using an oxygen-enriched
air breathing mixture.
The first commercial application of nitrogen-oxygen mixes of
other than normal air concentration was the self-contained dress of the
Westfalia Machinenfabrik in Geisenkirchen, Germany. In 1912 they used their suit with a
mixture of 45% O2 and 55% for depths to a 100 feet and a 30%
O2 mix for diving to depths of 200 feet. This suit, or the Nitrox
blend did not receive wide distribution. Based on this work, in 1913 Draegerwerk
produced a similar device that automatically mixed nitrogen and oxygen supplies
to produce a 60 percent O2 mix. About this time a rebreather device
attached to a cart (pulled by a boat) to allow passengers to tour the underwater
world was reported in Scientific American. The author suggested that underwater
touring might become a new recreational activity. Some time before WW I, the
Fleuss-Davis SCUBA unit appeared. This device consisted of two 10 cubic foot
tanks; one each for compressed air and oxygen. The gases were mixed in a
manifold between the two tanks and the diver's mouthpiece. The manufacturer
claimed success of this unit to depths of 66 feet.
Between the two world wars Siebe Gorman & Co. introduced
the technique of using different concentrations of oxygen mixed with nitrogen.
It had been established that divers could not tolerate oxygen concentrations
greater than 2 Ata for extended periods of time without difficulty. The divers
affected by this incapacity and convulsions associated with high O2
concentrations invented a mythical monster, "Oxygen Pete," who was supposed to
lurk on the bottom of the sea waiting to molest unwary divers. Oxygen toxicity hits during this time
were referred to as "getting a Pete."
Perhaps the best-kept secret of WWII was the use of
oxygen-enriched air re-breathers by the British commandos defending Gibraltar.
Those attacking the British stronghold were using 100% O2
re-breathers. The deeper maximum operating depth of the British mixes (45-60%
O2) was a distinctive underwater combat advantage since opposing
divers (using 100 % O2) would be at “convulsive depths” while the
British divers was still within their operating parameters. A major component of
the British strategy was to simply take the opponent down until convulsions
overwhelmed the enemy diver. This secret was so well kept, that much of this was
not even revealed to the US Navy until the 1950’s.
One interesting feature of the British combat protocols was
the definite association between CO2
build-up and increased susceptibility to oxygen toxicity seizures.
Their orders forbade rapid swimming unless “demanded by enemy contact.” Much of our present knowledge of oxygen
enriched air mixes can be traced directly to the British research efforts on
oxygen and oxygen-enriched air breathing mixes conducted during
Since it was known that increased oxygen (decreased nitrogen)
increased time available bottom time without decompression obligation in the 60
-100 foot range, a number of mixes were utilized primarily by the commercial
diving community during the period following WW II. Workman developed
decompression schedules for nitrogen-oxygen and helium-oxygen diving and
published these tables in 1965.
In the late seventies, the Canadian research institute DCIEM
was asked to develop a diving apparatus for the Canadian military to be used in
clearing mines. The ideal system would not disturb mine sensors that would
detect motion, magnetic fields, and/or sound. It was decided to utilize a
semi-closed system that would use a nitrogen-oxygen mix that would vary in
O2 concentration at depth to supply a constant pO2. The
constant pO2 is delivered via a pneumatic manifold, as opposed to an
electronic pO2 sensor controlled relay system. This system was made
available in the late 80's.
In 1978 NOAA formally established procedures for a standard
mixture of 68% N2 / 32% O2. It is known as NOAA Nitrox I. A second
standard mix that contains 36% O2 is known as NOAA Nitrox II. Since
that time, a number of users, including the US Navy, commercial and academic
diving operations have successfully used Nitrox in operations shallower than 130
feet. NOAA has developed a reasonable compact shipboard continuous gas mixing
system to supply Nitrox for diving operations.
During the last five years, approximately 28,000 logged dives
using Nitrox were surveyed. Although rigorous statistical analysis is not yet
complete, the trend is that Nitrox is a safe, easily handled mix when used by
properly trained divers. Two different agencies, ANDI and IAND, have been formed
to introduce this technology to the sport diving communities. The sanctioning of
Nitrox training by recreational training agencies NAUI and NASDS indicates that
Nitrox mixes are becoming a permanent part of the sport diving
improvement may here after be made in diving I will not pretend to say; yet I am
convinced that there can be much progress in the art." Johnny Green wrote these
words in 1859. They are still valid!
Brauer, R. HYDROGEN AS A DIVING GAS, Undersea and Hyperbaric
Medical Society, Bethesda, MD. 1987, 336 pages.
Davis, R. DEEP DIVING AND SUBMARINE OPERATIONS, St. Catherine
Press, London, England, 1962, 713 pages.
DeLatl, P. & Rivoire, J. MAN AND THE UNDERWATER WORLD,
G.P. Putnam's Sons, New York, NY. 1956, 400 pages.
Donald, K. OXYGEN AND THE DIVER, SPA Lyd. Worchs. Great
Britain, 1992, 238 pages.
Loach, N. "The Deepest Dive: A Study In Controlled Paranoia",
Ocean Realm, Summer, 1988, p.80-89.
Dugan, J. MAN UNDER THE SEA, Collier Books, New York, NY.
1965, 443 pages.
Gilliam, B. et. al. DEEP DIVING, Watersport Publishing, San
Diego, CA. 1992, 254 pages.
Green, J. DIVING WITH AND WITHOUT ARMOR, Faxon's Steam Press,
Buffalo, NY, 1859, 62 pages.
Hamilton, R. WORKSHOP CONCLUSIONS, Scuba Diving Resource
Group, Boulder, CO, 1992, 22 pages.
Larsen,H. A HISTORY OF SELF-CONTAINED DIVING AND UNDERWATER
SWIMMING, National Academy of Sciences, Washington, D.C. 1967, 50
Marx. R. INTO THE DEEP, Van Nostrand, New York, NY. 1978, 198
Miller, J. & Koblick, LIVING AND WORKING IN THE SEA, Van
Nostrand Reinhold, New York, NY. 1984, 433 pages.
Rutkowski, D. NITROX MANUAL, Hyperbarics International, Key
Largo, FL. 1989, 103 pages.
Schilling, C. A HISTORY OF THE DEVELOPMENT OF DECOMPRESSION
TABLES, Undersea Medical Society, Bethesda, MD. 1981, 131
Smith, E. TECHNIQUES FOR DIVING DEEPER THAN 1500 FEET,
Undersea Medical Society, Bethesda, MD. 1980, 159 pages.
Vallentine, R. DIVERS AND DIVING, Blandford Press, Poole,
Dorset, England, 1981, 169 pages.
Zinkowski, N. COMMERCIAL OIL FIELD DIVING, Cornell Maritime
Press, Cambridge, MD. 1978, 316 pages.
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Larry "Harris" Taylor, Ph.D. is a biochemist and Diving Safety
Coordinator at the University of Michigan. He has authored more than 100 scuba
related articles. His personal dive library (See Alert Diver, Mar/Apr, 1997, p.
54) is considered one of the best recreational sources of information In North
During the late 1980's and early 1990's the introduction of oxygen-enriched air as a breathing mix was a most controversial topic. It gave rise to a series of "anti" articles in some recreational dive magazines of the day. One major training agency, in particular was against using the gas in training. An article appeared in a major recreational diving magazine of the day denouncing "nitrox" as a new gas that had not been around long enough to evaluate. This upset me 'cause I knew that was simply not the case. So, I investigated the history of the gas and wrote the above article.
After submitting the article, an editor called me and told me that MY OPINION that oxygen-enriched gas had been used prior to the 1950's was absolutely false and, as such, the magazine could NOT publish the article. I pointed out that I had listed a number of valid references that clearly indicated the use of oxygen-enriched breathing mixes during the 1850's in chambers and the late 1870's underwater. The editor said, "AGENCY X says nitrox is a new gas and therefore you MUST BE Wrong! If you rewrite this piece as a letter to the editor, we will publish it as an opinion, but not as an article.
So, I rewrote the above information as a letter and sent this draft to IANTD, which published the article. Later, this article was expanded to include other gases (Brief History of Mixed Gas Diving )
At the time I was amazed at how readily some will dismiss scientific and historical fact merely to comply with "editorial policy."
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