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 use.   

All rights Reserved.

This is the oxygen-enriched air section of my article the history of mixed gas diving.   

Divegeek Content Page:   Home     About "Harris"     Articles      Slides     War Stories     Editorials     Links    Fini

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 concentration. 

Henry 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 strong-hold 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 were 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 WWII. 

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 community.   

My Nitrox Course Slides are at Oxygen Enriched Air Diving


"What 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 pages. 

Marx. R. INTO THE DEEP, Van Nostrand, New York, NY. 1978, 198 pages. 

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 pages. 

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. 


Divegeek Content Page:   Home     About "Harris"     Articles      Slides     War Stories     Editorials     Links    Fini

About The Author:

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 America.

  Article History

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, (with notice that your observations are not supported by facts) 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 / marketing policy."

  Copyright 2001-2022 by Larry "Harris" Taylor

All rights reserved.

Use of these articles for personal or organizational profit is specifically denied.

These articles may be used for not-for-profit diving education