The propriety of sport divers utilizing advanced or specialized equipment, diving into environments more hazardous than "typical" open water environments, or practicing diving techniques not considered to be within the realm of "recreational" diving has traditionally generated controversy. Past and current examples of debatable practices include penetration wreck diving, alternate second stage use, cave diving, planned stage decompression diving, buoyancy compensator use, oxygen decompression, ice diving, rebreather based SCUBA systems, and solo diving. The use of gas mixtures other than air also fall into this category. In this month's column, we examine the question of nitrox training and use.
While nitrox mixtures include air with both lower and higher percentages of the oxygen component than that found in air, all of the respondents considered only the type of mix in which the oxygen percentage was increased. The proponents who favored NAUI offering training in nitrox use, as well as many of those opposed to such specialty training, agreed that there were several benefits to an enriched air nitrox (EANx) mixture, including: longer bottom times, a greater safety margin with regards to decompression sickness, shorter surface intervals, and reduced decompression obligations.
Other non-physiological benefits detailed were the opportunity for market expansion and development opportunities, and the prospect for additional continuing education programs. The most persuasive argument raised was that since the numbers of sport divers using nitrox is rapidly escalating, that NAUI would be negligent in not providing training for those desiring it.
The majority of the members submitting opinions opposed a nitrox diving specialty program (60/40 against). The arguments they advanced were primarily technical, including the lack of a readily available and safe nitrox mix gas supply, the need for oil free compressors, the need for equipment designed and cleaned for oxygen use, and the increased complexity and hazards involved in recompression treatment of divers with DCS or embolism problems after diving with nitrox. Some of these problems could lead directly to cases of oxygen toxicity or decompression sickness.
The majority also felt that nitrox use was too complex and expensive for the average sport diver. Looking at the number of accidents which occur by divers improperly using air, a mix requiring a relatively simple set of procedures; the consensus belief was that more control over nitrox use is required. A common fear was that standard safety precautions used in the commercial or scientific communities would be ignored because of the expense, for example analysis of the final mix because of the high cost of the oxygen analyzing equipment.
Polarization in beliefs regarding the physiological safety of nitrox use also existed. While the U.S. Navy, commercial diving companies, and scientific divers have all been using nitrox for many years, there is a paucity of published data on the reliability of that use. Some of the respondents therefore feel that nitrox use should be considered experimental, until controlled research is conducted. Activists counter this by pointing to the large number of dives which have been successfully executed in a wide variety of environments and by an assortment of different groups.
Ultimately, the question comes down to a question of risk. Certainly, nitrox use entails more risk than does the use of air for diving in today's recreational community. The question of risk as posed by most of the respondents, however, looked to the actual use and/or abuse of nitrox as a breathing medium. Evolution in equipment and techniques, especially in the area of gas mixing, could do much to ameliorate this danger.
I would, however, pose the question of risk differently...if training in nitrox use is not available, would the number of divers injuring themselves be greater or less than those who would do so because of the increased use of nitrox if training was available? Regardless of whether or not NAUI sanctions training in nitrox diving, abuses will occur. We cannot prevent all misapplications, and must expect accidents and fatalities to occur. If we fail to provide accessible training, then mishaps will occur as divers blindly misuse nitrox as a result of inadequate knowledge. If we do offer training, accidents will occur because of wider use and carelessness. As dive industry leaders, we must decide which is the proper course to follow to insure that the industry remains as safe as possible.
QUESTION: "Should NAUI offer training through a specialty program in Nitrox Diving? Why/why not?"
A. This is a tough question to answer. On one hand, use of nitrox or other mixed gasses historically do not fit into the definition of "sport diving." However, divers are using dive computers in such a manner that a few years ago also was not defined as sport diving. This is acceptable procedure today.
On the other hand, if the market is using nitrox, and the need for education is growing, then NAUI should consider instituting a specialty course in nitrox diving. After all, our motto is "Safety Through Education." Since nitrox use is increasing, we should implement a Nitrox Diving specialty program.
--Struther MacFarlane, NAUI 6676; Toronto, Ontario, Canada (As a private professional educator, has taught all levels from introductory to serving as ITC Director. Recipient of the NAUI Canada Silver Pin and Special Recognition Awards.)
A. In a commercial or scientific diving setting controlled by a diving control board with an on-site diving supervisor, I have no problem with mixed-gas diving. Virtually all recreational diving has little to no supervision, and 99% of all divemasters and instructors know nothing of supervising a mixed-gas dive. After almost 28 years as a teaching organization, I sometimes wonder if we have even yet figured out how to keep divers safe on air. Now here we go toying with the idea of giving these same divers a breathing mix that depending upon its composition cannot be taken below 130 feet or 100 feet for fear of oxygen toxicity.
--Jim Corry, NAUI 7184L; Washington, D.C. (Has taught all levels to ITCs both privately and at UCLA. Currently serves as Chairman of the Diving and Water Rescue Committee of the National Association for Search and Rescue. Has authored many articles about diving safety. 1989 Recipient of the Greenstone Award.)
A. Yes, because it would help the liability exposure facing the training organizations. Our diver population is aging, and using an Enhanced Air Nitrox (EANx) mixture for these divers can enhance their safety margin physiologically.
Training is vital with this type of diving. It is important that the divers understand Equivalent Air Depth (EAD) and oxygen toxicity concepts, to prevent abuses of these gas mixtures. But we must remember that WE WILL NOT PREVENT ALL ABUSES. There have been and continue to be numbers of divers who abuse compressed air use. We must expect the same with nitrox use.
EANx will also open a new market for dive stores, both in equipment sales and especially with continuing education. Very little new equipment is needed by the divers--only nitrox dedicated cylinders. The major expense can be borne by the dive stores (mixing systems, oxygen analyzers), which can spread the expense across a very large diving base population.
--Billy Deans, PADI OWSI 9283; Key West, Florida Keys, FL (Teaching since 1978, owns Key West Diver, Inc. dive store. Has extensive experience with nitrox diving and other mixed gas media.)
A. I do not feel that nitrox use is appropriate for sport divers. Our understanding of the physiological effects of this kind of exposure is deficient with only minimal documentation being available (ie. in the public domain at least). Further, additional knowledge and care is required for safe gas mixing, testing, and calculation of decompression status, especially if a "dial-a-mix" system is employed. Although these skills can surely be taught, I believe that the fundamental argument is clear. Any mixed-gas diving (such as nitrox) is more complex than air diving and the added degree of environmental manipulation is outside the acceptable parameters for a recreational activity.
--Neal Pollock, NAUI 7068; Vancouver, British Columbia, Canada (Diving Officer for the University of British Columbia, and current President of the Canadian Academy of Underwater Sciences. Past candidate for the NAUI Canada Board of Directors.)
A. Unless there is firm evidence that makes nitrox incompatible with safe diving practices we should learn as much as we can about it and help educate the diving public as to the best way to use nitrox. A specialty course might be the easiest way to impart that information.
‑‑Bob Widmann, NAUI 2055; Aptos, CA (Past Mid Pacific Branch Manager. Has taught all levels of diving, including having served as ITC Director. Recipient of NAUI Outstanding Service Award.)
A. NAUI should not implement a specialty course in Nitrox Diving at this time. We still do not have enough experimental data with nitrox tables to sanction their use with humans. For example, there is no research which has been done using nitrox in repetitive diving situations. More animal research should be done before nitrox use is routinely used by divers. Once the animal research is completed, then 10,000-15,000 documented dives with people should be conducted on an "experimental" basis before NAUI considers endorsing such a program.
There also are potential problems with nitrox use once it is approved. One such are the problems and risks involved with recompression chamber treatments, especially if the chamber personnel do not realize that the diver(s) was using nitrox during the dive. This complicates the oxygen toxicity problems, as an increased oxygen toxicity problem exists even after the dive is completed.
Another major problem relates to the mixing procedures used to get the nitrox breathing media. I am amazed that more people in Florida and other locales where nitrox is commonly used have not had more mixing-related accidents. At least two gas analyzers should be used to measure final oxygen content, and this is not routinely done by those groups.
This issue should not be ignored. More research should be done, and educational articles discussing both the benefits and increased risks of nitrox use should be written. It would not be inappropriate for NAUI to publish such articles in Sources to inform the membership of progress which is made.
--Art Bachrach, PhD; Taos, New Mexico (Past Director of Environmental Stress Program Center and Chair of Science in Psychophysiology, Naval Medical Research Institute; and Adjunct Professor of Medical Psychology, Uniformed Services University of the Health Sciences. Current member, NAUI Board of Advisors. Has authored many papers and textbooks on stress and diving.)
A. OK, why not?
--Jerry Schnabel, NAUI 2464; Bonaire, Netherlands Antilles (Photo pro for Divi Resorts in Bonaire. Has taught primarily Underwater Photography specialties, but also has entry level thru ITC teaching experience at many resorts in the Caribbean.)
A. Nitrox diving must be done correctly. Special gas mixes can be used in the recreational community if it is done correctly. If a person is technically qualified and motivated enough to acquire the proper equipment to use special gas mixtures properly, then using an enriched air nitrox (EANx) could lead to a lower of risk decompression problems than using air. But to get to that point, EANx must be employed precisely.
The big problem with divers who receive inadequate training or no training and make procedural mistakes while using nitrox. The primary risks include: (1) oxygen toxicity from using an improper mix (final gas mix was not analyzed), (2) inadequate decompression from using an improper mix, and (3) the technical risk of handling 100% oxygen, especially in the typical dive store environment.
However, people are using nitrox. The divers using it are not breaking any laws, so they will continue to use nitrox and convince others to do so also. The dive training agencies should not ignore this problem--it is not going to go away. The certification agencies cannot avoid addressing this problem, it is inevitable that they develop training standards and procedures to address the nitrox diving issue. Training in nitrox diving should be provided.
--R. W. "Bill" Hamilton, Tarrytown, NY (In 1964 started work in laboratory of Union Carbide Corp. for Ocean Systems doing commercial diving research related to gasses and physiology. Since 1977 has been President of Hamilton Research Ltd. working as a gas physiology consultant for a variety of navies and commercial firms.)
A. Diving on nitrox with SCUBA, for the average diver, is probably not much different than diving with air. Very little change other than using different tables, specially cleaned gear, special testing equipment, and having to find a special supplier exist. But for these reasons, and others, nitrox diving is not for the average recreational diver and definitely requires special training.
My primary objection to the use of recreational nitrox diving is not with the diver--it is with the source of the gas. Nitrox, by definition, is a mixture of nitrogen and oxygen, to the exclusion of all other gasses. For breathing by divers both gasses should be medical grade and certified. Most operations I have heard about are really using "sweetened air" rather than true nitrox. Air tends to be somewhat dirty by graded standards, but divers are used to it. In our operations here at the Catalina Hyperbaric Chamber we use a 47/53 nitrox mix--purchased, not mixed locally. I have done gas mixing with both nitrox and heliox (helium and oxygen) breathing mixtures. For the well trained technician, mixing is not a problem; however for the "high school kid in the shop" filling tanks and maintaining the proper mixture could be. (But then, every good nitrox diver should carry around his own oxygen analyzer anyway.)
NOAA Nitrox I is the most popular nitrox table being talked about today. If NAUI cannot accept any of the newer, well tested, and proven air tables available how can they plan to adopt experimental nitrox tables? Yes, the NOAA tables have been in print for many years, but how much formal testing has been done on them? If the nitrox mix varies by as much as 1% from standard (32% oxygen), the NOAA tables are no longer valid. What tables do you use then?
And do not forget oxygen cleaning. Many proponents are suggesting that special cleaning is not required for mixes with less than 40% oxygen. A more acceptable standard is probably 25% oxygen. Any time a breathing mix exceeds 25% oxygen the equipment requires special cleaning, and perhaps having some of the parts exchanged for more oxygen tolerant materials. Once air has been put to the specially cleaned gear it should be considered contaminated, and recleaned prior to using "sweet" mixes again.
NAUI should stay out of the business of nitrox. Leave it to those few specialists who have the experience and knowledge to pass on their training to those few who need the special skills.
--Ronald J. Ryan, NAUI 7205; Two Harbors, Catalina Island, CA (Supervisor, Catalina Hyperbaric Chamber. Past employee in the commercial diving industry, where his duties included mixing special gasses for diving.)
A. Nitrox was in use before most divers in this country were born. For decades, the U.S. Navy and commercial diving companies have successfully used nitrox mixtures for increasing diving efficiency. More than a decade ago, NOAA recognized the significant advantages obtained by the use of nitrox, and published tables and procedures for its use in the 1975 edition of the NOAA Diving Manual.
Only within the last 5 years has the scientific and advanced level sport diving community began to take advantage of the numerous benefits of nitrox (increased bottom times, reduced residual nitrogen times, reduced nitrogen narcosis, shorter surface intervals, and safety). Why safety? Simple. The existing Nitrox Decompression Tables (NOAA Nitrox I) are simply more conservative than the U.S. Navy Air Decompression Tables upon which they are based. Scientists from over a dozen universities have performed thousands of nitrox dives, as have progressive sport diving groups.
The demand for good training in nitrox diving has stimulated the formation of the International Association of Nitrox Divers, and American Nitrox Diving, Inc. Detailed information covering the advantages and limitations of nitrox, safe and efficient methods for its preparation, and equipment and techniques necessary for its use are all nitrox diving training programs. While the use of nitrox is not for all divers, its use has advantages for many. There is no reason that this information could not be provided for those individuals by the national certification agencies. [Ed. note: NASDS has at this time sanctioned the use of nitrox in a nitrox diving specialty course.]
--Dick Rutkowski, NAUI 4563; Key Largo, Florida Keys, FL (President of Hyperbarics International, which conducts training programs for divers and instructors in nitrox diving. Past diving officer for NOAA, where he helped pioneer the use of nitrox diving in research tasks.)
A. I believe that the concepts (equivalent air depth and the dive tables) that enriched air nitrox use is based on are sound. However, there has been very little actual testing/use to prove the safety of its use. It is my opinion that the use by the sport diving community, if approved, will provide the data base to validate these theories. This is not bad or unacceptable--the U.S. Navy tables had very little testing when they were released, and were validated through use.
If nitrox diving is approved by NAUI, however, then I believe that the existing tables should be slightly modified to provide a greater margin of safety.
My biggest concern with nitrox diving is the production of the breathing gas mixture itself. I have strong concerns about the ability of the average dive store employee to provide a safe mixture. The proper gas mix is critical to the safety of the diver--too high a percentage of oxygen, and the diver could develop oxygen toxicity. Too little oxygen, and the divers do not have the margin they are planning on with nitrogen uptake, and may get bent. If automated equipment was available that had very high reliability for providing the proper mix, I would be less concerned with approving nitrox use.
--Andy Pilmanis, PhD; San Antonio, TX (Currently involved in hyperbaric research for NASA in support of space program activities. Past Director of the Hyperbaric Chamber at the Catalina Marine Science Center at the University of Southern California. Has published extensively and lectured on diving safety and hyperbaric medicine.)
A. Having been asked this question quite frequently, I have several conversations regarding this with individuals from various certifying agencies, insurance companies, dive shops, and sport divers in the truest sense. To speak of nitrox, most people tend to dwell on the bottom time advantage. This is quite impressive in many cases, but there are other issues.
1. From a practical sense, the cost is prohibitive for most people, since one must purchase oxygen analyzers, cylinders to dedicate to nitrox use, etc., which may run as high as an extra $1000.
2. A major concern would be that of control. Who is to monitor the fill stations' mixing procedures and quality of gas? Who sets the standards? There appears to be enough difficulty in dealing with air.
3. We know from discussions with sport divers and with the growing interest in dive computers, that divers are conducting multi-level diving. With nitrox, a great deal of this flexibility is lost. Once a depth is determined for that given mix, one cannot descend any deeper. Therefore, a depth must be strictly adhered to with no option for going deeper. Once this is realized, many of the divers inquiring about nitrox realize that it is not quite what they thought.
4. From discussions with individuals in the insurance field, it does not appear that they are willing to support nitrox use. A great deal has been written regarding nitrox, with the majority of the agencies have publicly stated that they are against nitrox use, so the insurance companies do not seem supportive at this time. The current question is, if a diver gets injured now, will he/she be covered since nitrox diving is not currently considered "recreational" diving?
5. From a treatment standpoint, it is quite common for the injured sport diver to be inaccurate relating dive profiles. Without being derogatory about the divers' intelligence or competence, it is a common observation that the divers admitted for treatment have not paid close attention to their profiles. If this is the case with air, perhaps we may want to reevaluate diver training again before embarking on an ambitious project such as nitrox.
I am not presently supportive of nitrox use in sport diving. It is difficult for me to say this; being a diving physiologist I certainly appreciate the safety/health factors it provides. I would support nitrox use in the sport diving community if three things could be accomplished: (1) All divers were trained in its use since it would be readily available, (2) all stores were educated in the proper mixing procedures and followed the same standards, and (3) the insurance companies support its use so that any litigation would be covered and all accident-related problems were covered.
The question must be asked, "Do the benefits outweigh the risks?" Only the agencies can answer this.
--Dudley J. Crosson, PhD, NAUI 8838; Port St. Lucie, FL (Owner of Delta P, providing services to firms needing specialized supervision and training in advanced diving technologies, including special gas mixtures. Past Diving Safety Officer/Diving Physiologist for the Florida Institute of Technology Underwater Technology Program, and Diving Officer at the Harbor Branch Oceanographic Institution.)
A. NAUI has always stood for "Safety Through Education." Once a new method or technique, such as nitrox, has been refined and is ready for implementation by the sport diving community NAUI should offer the appropriate training and certification. It is questionable whether sport diving has a legitimate need for this technique considering the increased complexity of diving operations versus the benefits from increased bottom time. I do not feel that presently all facets of this technique have been investigated to the level required for widespread use by the general diving community.
Our diving staff at the National Undersea Research Center implemented an enriched air (nitrox) program in 1986 for support of ocean science investigations. To date, we have made over 600 dives using enriched air between 60 and 130 fsw with no incidents. We feel this safety record is due to the care and special attention paid to equipment and technique by our professional staff.
Diving an EANx mixture is, for the diver, no different than air. The equipment worn and the procedures used are generally the same. However, EANx diving requires the diver to be well versed in such topics as: central nervous system oxygen toxicity, equivalent air depth, partial pressures of oxygen, and nitrox repetitive diving tables. The diver should also be instructed in gas mixing techniques and gas analysis even though others (such as a dive shop or resort) may be responsible for this function. All these topics could be properly covered by NAUI instructors through a nitrox specialty course.
The gray area with enriched air is equipment, which can be split into two types, diver-worn and gas mixing equipment. Any equipment exposed to concentrations of oxygen greater than air must be designed for such service. Because SCUBA equipment is designed for use with air, the materials and lubricants used may not be safe for EANx mixtures. In an effort to answer some questions in this area I canvassed all major manufacturers of SCUBA equipment (via questionnaires) asking if their cylinders, regulators, and/or BCs were compatible with enriched air use. I received little response and concluded this was due to the fact that most major manufacturers have not yet determined whether or not their product can be safely used with EANx mixtures. Mixing equipment is a problem because there is not a commercially available enriched air mixing system. Each enriched air station must be custom designed and built without the aid of specific guidelines. If this is not done correctly by knowledgeable persons, serious problems can arise. Gas mixing using pure oxygen is at best an art and at worst extremely dangerous.
Enriched air diving is a safe and proven concept. However, we must wait for new developments in equipment technology before widespread use by the sport diving community should be considered or endorsed. Recreational diving is still viewed by the majority to be a high risk activity. Great strides have been made toward disproving this notion, and it would be a disservice to the sport to let a few zealous individuals lead us too far too fast. NAUI must live up to the ideology of safety first.
--Stephen J. Mastro, NAUI 6094; Wilmington, NC (Diving Coordinator for NURC/UNCW, trains scientific divers in advanced diving techniques, designs and constructs enriched air mixing systems. Published papers on operational use and mixing of enriched air.)
A. Nitrox is a gas mixture of oxygen and nitrogen in different proportions than those found in the air (or compressed air) we breathe. Getting the proper mixture may be tricky stuff: if your mix has too much nitrogen, you may not get the expected benefits of reduced narcosis and increased no-decompression limits. If it does not have enough, the partial pressure of oxygen might get too high then: beware of oxygen toxicity!
With compressed air, the 80% N2 -- 20% O2 mixture is easy to remember, and all our dive tables and computers take those percentages for granted. With nitrox, an almost infinite number of mixture combinations is possible...the decompression profile will then undoubtedly change but to what table should you refer to for your special mix? It is too easy to get a "wrong" mix, I therefore disagree with the idea of any specialized course in nitrox for sport diving.
--Martin Poirier, NAUI 10040; Cartierville, Quebec, Canada (Teaches part-time for Ecole de plongee sous-marine Triton, a NAUI Pro Facility. Teaches primarily Openwater I classes, and enjoys ice and wreck diving.)
A. Equivalent Air Depth (EAD) sounds like a reasonable concept, but it has not yet been proven. Before nitrox diving is accepted as a "safe" standard, the concept needs experimental validation. A minimum of 50,000 dives should be conducted under supervised conditions with each gas mixture before that mixture and associated tables are routinely utilized.
Dives which have been conducted using "home-brews" mixed in a garage should not be included in this data base. There is no control on such dives, and no post-dive standardized reporting mechanism. The content of the gas mix used in these dives is especially suspect, as at least two calibrated oxygen analyzers should be used to verify the mixture prior to diving.
You do not get something for nothing. Before toting "doubled no-decompression bottom times" and "increased safety margins," the increased risk of oxygen toxicity should be considered. The mechanisms behind oxygen toxicity are poorly understood, and also require more experimental data.
Because of these factors, I do not feel that the time is right for NAUI to consider implementing a Nitrox Diving specialty course.
--Dr. Glen Egstrom, NAUI 937L; Los Angeles, CA (Dive Officer for University of California, Los Angeles. Member NAUI Board of Advisors. Past President NAUI. Has taught all levels from Entry level to ITCs. Has authored many textbooks and articles on diving safety, and has lectured extensively. Recipient NAUI Outstanding Service Awards.)
A. The use of various nitrox mixtures has been around for years, only recently having been considered by recreational divers. Historically, it has been of significance only to commercial and research interests in terms of the cost/benefit ratio. The benefits are that bottom time is extended and the decompression obligation is reduced due to lower nitrogen partial pressures. These groups exercise their technological capability to precisely mix, analyze (with redundant oxygen analyzers) and properly supervise the application of nitrox.
If we try to justify use of nitrox by the recreational community based on its successful use in either the scientific or commercial communities, we immediately see that problems exist. Nothing remotely close to the same level of organization, technical discipline, or emergency support currently exists within the general recreational diving population.
The cavalier attitude demonstrated by many sport divers could lead to short cuts in the gas mixing process, and the creation of "home brews." Errors in mixing or applying the mix to dive tables could result in oxygen toxicity or decompression sickness. If an incident were to occur, the effectiveness of appropriate chamber treatment might be compromised due to the cumulative toxic effects of recent exposure to high partial pressures of oxygen.
Considering these risks, where are the benefits? In order for the risk/benefit ratio to favor nitrox use, the increase in bottom time must be significant, since reduced decompression obligation has little value to a population who supposedly do not conduct decompression dives. While the potential of increased bottom time does exist, the DCS risk inherent in the selected set of tables must also be examined. Conservative tables lower the risk of DCS but generally do not provide the desired increase in bottom time. In the use of nitrox, as with decompression diving, the risk/benefit ration may not favor the diver. From this perspective, it may be better to err with air.
--Dan Orr, NAUI 5612; Tallahassee, FL (Assistant Director and Associate Diving Officer of the Academic Diving Program at Florida State University. Former NAUI Mid-America Branch Manager. Has authored numerous articles on diving safety topics, as well as spoken on nitrox use at a variety of diving symposiums. Recipient of the NAUI Outstanding Service Award.)
A. NOAA Nitrox I (32/68), when used correctly and according to the instructions, is more safe for divers than air. Ignore the clearly defined protocols and, as with anything, the dangers increase with the magnitude of the individual's stupidity. Training to use Nitrox I correctly is short but essential. The rules for its safe use are neither complex nor too long to remember. Nitrox I must not be used at depths greater than 130 feet, and it must be blended in a precise and accurate way. Unfortunately, some not so precise methods are in use today and there is no safety net at the maximum allowable depth to stop those who do not understand why the gas does not allow deeper diving.
Divers have some options, depending on their needs, in how they choose to take advantage of Nitrox I. In general, bottom time is nearly doubled if the diver needs that time. However, when far from a hyperbaric chamber, the "enriched air" diver may use standard air tables and benefit from a greatly increased safety margin.
Quality training in all phases of nitrox use is now commercially available. Those who criticize the use of nitrox by sport divers, including some leaders within NAUI, should take the training. They might recognize the dive industry is at exactly the same place with Nitrox I today that we were with cave diving 15 years ago. Some dedicated leaders said then we should ban cave diving (a classic example of putting one's head in the sand). Clearer heads held that experts in the cave diving associations should lead the way. They did; and when pursued conservatively, cave diving risks are acceptable. The instructor associations should follow a similar path for safe introduction to Nitrox I as it can be the cutting edge of diving technology for the 1990's.
--Bill High, NAUI 175; Seattle, WA (Director, Professional Scuba Inspectors. NOAA Nitrox II trained mixer and user. Past President of NAUI, and recipient of NAUI Outstanding Service Award.)
A. No, I do not think NAUI should offer a specialty course in Nitrox diving. Nitrox is beyond the scope of sport diving. Being a professional diver as well as an instructor I have been involved in nitrox diving operations. The preparation and care for equipment used in nitrox diving is much more involved than that used with air diving. All equipment must be cleaned for use with oxygen and then only used for nitrox. This includes cylinders and regulators as well. Additionally the mixing and filling processes require extreme care. The gas must be analyzed before use and should be checked just prior to making the dive. An oxygen analyzer must be used for this check. A reliable analyzer will cost several hundred dollars. In light of the results of the dive table survey conducted recently at IQ, I do not believe that sport divers are ready to handle the complexities of table adjustments for nitrox. In short, I think that for sport diving the possibilities for problems far out weigh the benefits, and nitrox diving should be left to professional divers. -
-Frank J. Toal, Jr., NAUI 10185; Orlando, FL (Diving Systems Officer for the Living Seas at EPCOT Center, Disneyworld. Has taught Openwater I to Assistant Instructor courses, plus a wide variety of specialty classes. Former Diving Control Officer for Tampa Marine Institute.)
A. Emphatically NO!! I teach mixed gas diving, including nitrox, at a commercial diving school. I spend a minimum of 40 hours in the theory, mathematics, and mechanisms of the subject in the classroom before we begin an even longer practical module. Nitrox gas diving by far has the least research and the fewest verifications of the no-decompression and decompression schedules of all the possible gas mixes which we use in the commercial diving industry. In an industry where decreasing decompression time translates directly into more effective use of the diver (read more bottom time for the same amount of money), we still do not use nitrox diving to increase the no-decompression times for a given depth. On the contrary, because increasing the oxygen percentage causes adventure into the oxygen toxicity range, we set the potential for a greater danger than that of decompression sickness. And this is in an industry (offshore oilfield diving) where we have full-time topside supervision and support and highly trained divers; all working in their primary specialty of diving. A lot of this diving is shallow--less than 80 fsw--and using no-decompression, repetitive diving schedules.
Sport divers--recreational divers--would do well not to emulate or try to venture into commercial diving areas. How would they mix their gasses? How many instructors are qualified to teach such subjects involving compressibility coefficients of various gasses; the real-gas method of calculating partial pressures in a mixture versus the ideal-gas method; calculations of and methods used to adjust percentage of mixes (especially difficult in small cylinders such as used in scuba and without precise test gages); establishment of no-decompression limits and oxygen partial pressure/time limiting factors; etc. And once taught to some varying level of competency, how are we to assure the students will perform within the limitations once they are on their own? I feel we are looking at "liability city" here.
We are treading dangerous ground. Sport diving should constrain itself to just that and not venture into the realm of military combat diving and commercial diving, no matter how exotic the latter two may seem.
--Jim Haynes, NAUI 2115; Houston, TX (Teaches at The Ocean Corporation. Has taught at the USN Dive School, as a military advisor, semi- and closed-circuit UBA diving to Greek attack swimmers. Has worked as a military EOD and deep sea diver and supervisor, commercial diver, and offshore diving supervisor. Has taught sport diving from skin through ITC Director, and has been recipient of several NAUI Outstanding Service Awards.)
A. I understand that nitrox will or should reduce the number of decompression sickness accidents in sport diving. I am not convinced, however, that sport divers will follow the rules any better than they do now. I am under the impression that many of the DCS hits are a result of sport divers pushing the limits and bending the rules.
Another concern is the availability of nitrox. What guidelines will divers use when they make repetitive dives using air for one dive and nitrox for another?
The question is; should NAUI offer a specialty training program for using nitrox? I think we should get involved in training to insure that sport divers have the necessary skills and knowledge to use nitrox.
We are the premier diving educators and we should be leading the development of any training program that will help to make sport diving safer and more enjoyable. It appears that nitrox is going to be used by sport divers. NAUI needs to be involved with the development of safe diver training for using nitrox.
We should learn a lesson from the alternate air source evolution. It has been about 20 years since sport divers began attaching an additional second stage on their regulators for air sharing underwater. NAUI did not get involved in the development process, and consequently the training and use of these life saving devices is not standardized. Instructors still are unable to agree on the best methods for training divers how to use alternate air sources.
I hope NAUI decides to lead the development of educational programs for using nitrox and other sport diving innovations. Our role is "Safety Through Education."
--Tom Hemphill, NAUI 2491; Federal Way, WA (President of Emerald Seas Ltd, a professional diver training and consulting company; and General Manager of Emerald Seas Diving Center, a full service diving resort and training center on Orcas Island. Former NAUI National Sales Manager and Business Consultant. Has trained more than 3,000 divers at all levels up to and including Instructor.)
A. Breathing gasses other than air have been used for underwater consumption long before recreational diving became popular. These mixes have been applied to commercial, science, and exploration dives for the very same reason they are under consideration for the recreational industry today; with appropriate management they will provide a greater degree of safety and efficiency to the human diver underwater.
Perhaps our focus within NAUI should not be on the technology, but rather on how it is to be used. In my opinion, the availability of nitrox to the recreational community is inevitable. We should focus instead on what component of this new technology we do wish to define as recreational. No one will dispute that bandmask surface-supply gas diving is outside the realm of recreational diving, but a well managed alternative called hookah diving is a popular recreational rendition of the same technology. The recreational diving community has overcome and benefitted from the introduction of many new technologies (the LP inflator, alternate air source, buoyancy compensator, and recently the dive computer) by carefully and appropriately applying them to improve the safety and efficiency of its members.
NAUI has always stood for Safety Through Education, not ignorance or restriction. Our membership should learn as much as possible about this technology, encourage further research, and seek out appropriate renditions of this and future technologies for the recreational community we serve. History has taught us that if we fail to pursue new ideas, we leave it to others to define them for us.
--Gregg Stanton, PhD, NAUI ????; Tallahassee, FL (Director, Academic Diving Program, Florida State University; and Research Diving Coordinator. Has taught all levels of diving up to and including ITCs. Has conducted nitrox and mixed gas workshops for the American Academy of Underwater Sciences, and has authored many papers on various aspects of research diving.)
A. Nitrox, which is a mixed gas, has no place in sport diving. Mixed gas diving requires extensive and highly specialized training that is not practical for the sport diver. Mixed gas diving has many physiological effects on the body that differ greatly from air diving and also require a person to be in excellent physical condition in order to perform safely.
NAUI should not get involved in nitrox or any other mixed gas training. Let the commercial divers dive where mixed gas is warranted. We have a difficult time in training competent air divers, we do not need the extra burden of training sport mixed gas divers.
--Patrick Mark Cotter, NAUI Z7783; Carbondale, IL (Assistant Instructor at Bowling Green State University. Graduate of the Commercial Diver Training program at the Florida Institute of Technology.)
A. There is nothing strange or exotic about nitrox. In fact, we have been breathing a nitrogen-oxygen mixture (air = original nitrox) since birth. Until recently, the use of a varied mixture of nitrogen and oxygen has primarily been for military or scientific diving purposes. The National Oceanic and Atmospheric Administration (NOAA) has been using nitrox safely on scientific diving projects for over ten years. Nitrox is now entering into use by certain segments of the sport diving community. The temptation to use nitrox is understandable. It can appreciably increase bottom time with a decreased risk of decompression sickness and, as a side benefit, reduces the risk of nitrogen narcosis.
Any diver with a basic understanding of physics and a filler hose adapted to connect between an oxygen cylinder and a dive tank can change the nitrogen-oxygen ratio of their breathing mixture. Nitrox tables are available (NOAA Diving Manual) in a form that most divers can understand. The one essential ingredient missing is how to do it safely. Nitrox mixers (dive shops, clubs, or individuals) need to know the potential dangers of handling pure oxygen and that the equipment used to transfer and hold pure oxygen has to be oxygen clean. Nitrox divers must know the tolerable limits of increased partial pressures of oxygen. These needs can only be met with a well organized training program.
I personally believe that nitrox will be a standard breathing mixture for sport divers in the not too distant future and hope that NAUI is ready with a nitrox specialty training course to meet the demand.
--Ian K. Workman, NAUI 4232; Gautier, MS (Unit Diving Supervisor for NOAA Southeast Fisheries Center, and instructor for SeaSpace Dive Center.)
A. NAUI should not offer a specialty in nitrox diving. At the moment there are no special scuba cylinders for nitrox mixtures which does not make it impossible for a diver to confuse a nitrox filled cylinder for an air filled cylinder, or vise versa. The consequences of that small mistake could be devastating. What happens when divers or stores do not quite empty their nitrox filled tanks and carelessly refill them with air for other divers or dives? What happens when a diver who has used a mixed gas has a diving accident and needs hyperbaric treatment? What are the assurances that the doctor will know exactly what percent oxygen the mixture contained? How do we insure that the nitrox produced by all the stores meets exact specifications (whatever those are), and that their students are able to retain what they have learned in a two or three day course enough to be safe (we have trouble enough in getting them to drop a weight belt or read tables after a year)? Is it worth the extreme liability it involves? We do not think so. Our goal is to make diving safer, not to introduce "just another way for divers to possibly get hurt."
--Walt "Butch" Hendrick, NAUI 1724; Hurley, NY
--Andrea Zaferes, NAUI 10533
--George Safirowski, NAUI 8921L
--Walt "Sandy" Hendrick, NAUI ???? (All are instructors of Lifeguard Systems Inc. Butch Hendrick is a past Director of NAUI, and recipient of the NAUI Outstanding Service Award and the Leonard Greenstone Award, and author of Oxygen and the Scuba Diver.)
A. Successfully used by the National Oceanic and Atmospheric Administration (NOAA) and an ever growing number of research institutions during the past twenty years, nitrox's validity as a safe gas are beyond dispute. The concerns of safety alone should dictate NAUI's policy: the lack of professional, sanctioned training in the proper use of nitrox has led some divers to adopt improper and dangerous methods of creating oxygen/nitrogen mixtures. The motto "Safety Through Education" can and should be applied to the use of nitrox.
Rather than stand by and watch divers engage in imprecise and dangerous practices of gas mixing, NAUI should be blazing the trail in assisting those divers who wish to become educated as to correct procedures for mixing and using nitrox. By definition, a nitrox course must include gas mixing information, which is NOT to say that the course will qualify divers to mix their own gas. It is hoped that such information will lead to the discontinuance of dangerous and incorrect mixing practices.
Safety factors, such as gas distribution and use during training, can be addressed in the Standards and Procedures Manual. For example, we may wish to designate nitrox distribution centers to ensure a valid supply of legitimate gas. Because of possible oxygen toxicity complications when using NOAA Nitrox I, we may wish to limit nitrox training dives to areas where there is NO possibility of descending below 130 fsw.
Experienced divers who wish to use nitrox will not be (and are not) discouraged from its use because a certifying agency will not sanction it. Let us allow those with the experience and inclination to become more knowledgeable about correct and incorrect uses of nitrox. In this way, NAUI will further the advancement of safe recreational diving and continue to be a leader in the field of sport diving.
--Bernie Chowdhury, NAUI 10304; New York, NY (Teaches Openwater I to Advanced classes and Deep Diving specialty courses for Pan-Aqua Diving, Inc. Member of the International Association of Nitrox Divers.)
NOTE: The views expressed in this column are opinions held by the individual members referenced, and are not those of NAUI or the editors of NDA News.]Questions for the next issues:
Questions for the next issues:
For the January/February issue: "What could be done to improve the marketability of NAUI's products, programs, and services?"
For the March/April issue: "Given the multitude of dive tables on the market, which tables should be taught? Why?"
For the May/Jun issue: "Should instructors be required to have oxygen administration equipment and training to remain in teaching status?"
All members are encouraged to respond. This column is for you, the membership, to develop. Answers should be kept fairly brief, preferably no more than two or three paragraphs. Responses to each question will be collated by the editor, condensed if necessary, and printed in this section. New questions may also be posed for discussion. Questions should be concise, and should stimulate a wide cross‑section of the membership. Include with your responses or questions the following information: your name, address, phone number, NAUI membership number, dive‑related employment, past diving accomplishments, and a review of your dive teaching experience. Send your materials to Jeffrey Bozanic, c/o NDA News, P.O. Box 14650, Montclair, CA 91763‑1150.
Compiled and Edited by Jeffrey Bozanic, NAUI 5334L
Sources, Nov/Dec 1989, (1:4), pp. 8-13.
NAUI Members' Forum #14
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