Do you know how technical diving got its name, its history and evolution to its present status as the vanguard of diving? Read on to find out.

Though still regarded as crazy by some in the military and commercial diving circles, technical diving, which just turned 32 years old, is no longer considered the radical fringe and has taken its rightful place as the vanguard of sport diving. The history of diving is the story of the quest to go deeper and stay longer. Mixed gas is one of the technologies enabling divers to do that. The U.S. Navy was the first to develop mixed gas (specifically helium) diving protocols in the 1930s to rescue sailors from downed submarines. Commercial divers in the 1960s then developed their own protocols and methods as oil field diving pushed beyond reliable air diving limits[1].

This need to “go where no one has been before” was a driving force in the 1980s. It wasn’t uncommon for underwater explorers to conduct unsanctioned, relatively long 61-122 metre dives on air using oxygen for decompression, at their own peril. Even in the cave diving community, there weren’t any guidelines for diving beyond 40 metres.

In the mid-to-late 1980s, small groups of experienced divers led by pioneers such as Dale Sweet, Jochen Hasenmayer, Sheck Exley, Bill Gavin, Parker Turner, Bill Main, Lamar English, Billy Deans and others, began experimenting with helium mixes to push the limits of self-contained diving further. Diving physiologist Dr. R.W. “Bill” Hamilton and others such as former U.S. Navy medical officer Dr. John Zumrick and anaesthesiologist John Crea aided them by providing special mix decompression tables.

It seems remarkable today that explorers like Exley were conducting mixed gas cave dives as deep as 189-274 metres in the mid-to-late eighties. Cave environments offered confined water and ample areas for staging cylinders (and decompressing) which made it a more accessible proving ground for mix technology than open water.

The wreck diving community was also pushing air limits with 15-25 minute dives to 61-79 metres, mostly conducted on air using U.S. Navy tables or dive computers. Few were using oxygen for decompression. Billy Deans, owner of a Key West Florida dive shop, began developing mix protocols after losing his best friend on an air dive on the SS Andrea Doria in 1985. That year he helped Captain Steve Bielenda install an oxygen decompression system on Bielenda’s boat, the RV Wahoo, based in Montauk, New York, that got divers out of the water faster and with fewer bends. Soon everyone was decompressing with oxygen. Deans went on to create the first technical diving training centre and trained many Northeast wreck divers to dive with mix gas.

1987: The Wakulla project decompression habitat, where divers conducted most of their decompression. On board controls permitted up to six divers to ascend from 70 feet depth to the surface. Twelve-hour missions were not uncommon during the project. (Photo courtesy of US deep Cave Diving Team)

Arguably the poster child for mixed gas diving was the Wakulla Springs Project, organised by caver and engineer Dr. Bill Stone in the fall of 1987. In two and a half months, Stone and company mapped 3.7 kilometres of underground passageway at depths of 79 to 98 metres, using new technologies and techniques such as open circuit heliox with nitrox and oxygen for decompression, high pressure cylinders, long-duration scooters and an underwater decompression habitat. This was the first large-scale mixed gas expedition of its kind and marked the emergence of tech diving.

1987: Dr. Stone inspects the habitat at 60 ft/18 m during second test dive of the Cis-Lunar MK 1. (Photo by Noel Sloan)

Although they used open-circuit scuba, Stone knew rebreathers would eventually be needed to overcome the limitations of open circuit gas logistics for deep cave diving. With his team, Stone built a 165-pound prototype, the MK-1 fully redundant rebreather, trialling it in a 24-hour long dive.

In 1987, engineer Kevin Gurr (the future president of VR Technology Ltd.) began helping Carmellan Research Ltd. principal Stuart Clough, and British explorer Rob Palmer, with the electronics for their modified Mk-15 military rebreathers. The rebreathers combined with open circuit heliox, enabled Clough and Palmer to explore the Andros Blue Holes.

1987: British rebreather pioneer Stuart Clough instructing Rob Palmer on the use on the Carmellan Research CR155 rebreather (a modified Rexnard MK15.5 capable of maintaining a 1.4 atm set point) on Andros Island, Bahamas. Bill Stone in the background. aquaCORPS archive. (photo courtesy of Michael Menduno)

Clough then teamed up with British engineer Peter Readey (who later formed Steam Machines Inc. and designed the PRISM rebreather). In Europe, cave explorer Olivier Isler teamed up with engineer Alain Ronjat to build the RI 2000 semi-closed rebreather, which he used to push the La Doux de Coly siphon in 1989.

1989: Olivier Isler entering Doux de Coly with his fully redundant RI 2000 semi-closed rebreather. (Photo by Gavin Newman)

What’s In A Name?

In the early days, tech diving wasn’t widely talked or written about in the press or at dive industry forums like the Diving Equipment and Marketing Association (DEMA) show and there were no training courses. This lack of information made divers less safe!

1989: Sheck Exley preparing for his Manté expedition to 867 ft. (Photos by Randy Bohrer)

I started aquaCORPS Journal in January 1990 to change that. Our first tag line was The Independent Journal for Experienced Divers. In that first issue, we featured a Dr Bill article titled, Call It High-Tech Diving. At the time, I had a few rock climber friends engaged in what was then called, “technical climbing”, where individuals used ropes and protection to tackle rock faces that couldn’t be climbed. The word “technical” had all of the right connotations. So, I pinched the term for diving, using “technical diving” for the first time in aquaCORPS #3, DEEP (Jan 1991). In the next issue the tagline became The Journal for Technical Diving and ­technicalDIVER, a companion newsletter, was launched.

1990: Woodville Karst Plain Project (WKPP) co-founder 1990 Parker Turner decompressing at the Habi-trough in Cheryl Sink. (photo from aquaCORPS archives courtesy of Michael Menduno)

Later that year, Drew Richardson, then a vice president of the Professional Association of Diving Instructors (PADI), penned Technical Diving – Does PADI Have Its Head In The Sand?, an editorial for PADI’s Undersea Journal, which helped legitimise tech diving as distinct from recreational diving. And the name stuck!

Nitrox: The Devil Gas

The “technical diving revolution” was really about adapting mixed gas technology to the consumer market. Mixed gas could improve divers’ safety and performance and enable them to extend their depth and bottom time by optimizing their breathing gas for the planned exposure. This meant you could, a) Maintain efficient and reliable oxygen levels over the course of the dive, b) Reduce/eliminate undesirable inert gas effects such as narcosis and HPNS and to facilitate off-gassing and, c) Reduce breathing gas density to minimise the work of breathing and prevent CO2 build-up.

With the 40-metre depth limit of PADI “deep divers” serving as merely the first decompression stop for most tech divers, recreational diving instructors no longer represented the apex of the sport diving food chain. In addition, while once considered the mark of the elite, diving beyond 67 metres on air was now considered increasingly foolish. Dick Rutkowski, a former aquanaut and deputy diving director for the National Oceanic and Atmospheric Administration (NOAA), founder of the International Association of Nitrox Divers (IAND), and co-founder of American Nitrox Divers Inc. (ANDI), was also promoting nitrox for recreational diving.

Dick Rutkowski analysing his nitrox. (Photo by Bret Gilliam)

Not surprisingly, there was pushback from the recreational diving industry, which had little knowledge of nitrox or mixed gas technology and was concerned about safety. In the Fall of 1991, Bob Gray, the executive director of the Diving Equipment and (then) Manufacturing Association (DEMA), decided to ban nitrox vendors and training agencies like IAND and ANDI from attending the DEMA annual trade show.

With the help of Dr. Bill, Diving Unlimited Inc. founder and CEO Dick Long with his Scuba Diving Resources Group, and Richard Nordstrom, then CEO of Stone’s company Cis-Lunar Development Labs, we organised the Enriched Air Nitrox (EAN) Workshop in January, 1992 in Houston, Texas, days before the DEMA show was to be held there. Our goal was to bring all the stakeholders together to discuss nitrox and its uses. In light of the workshop, Gray agreed to rescind the ban on nitrox vendors attending the show.

1994 Diver sporting the Cis-Lunar Development Laboratories MK-IV rebreather (Photo courtesy of Michael Menduno)

As a result of the EAN workshop, the sports diving community established the first set of policies addressing for the use of nitrox, and that nitrox could be used by all sport divers. We published the findings from the workshop written by Dr. Bill in aquaCORPS’s sister publication technicalDIVER Vol. 3.1, published in July 1992.

That year, the first page of the DEMA Exhibitor’s Guide offered a warning about using nitrox with scuba equipment. Ironically, that highlighted nitrox to attendees and proved to be great advertising for mix gas technology and the training agencies.

Developing Community Standards and Best Practices

The summer of 1992 was a tragic one for the fledging tech diving community. There were eight high-profile diving fatalities, including two on the Andrea Doria, and one at Ginnie Springs cave system in Florida, along with a number of close calls that resulted in injury. Many feared that these deaths would bring on government regulation and effectively shut down technical diving.

1991: “This is Not Recreational Diving!” Tech pioneer Wings Stocks preparing to dive the Doria during the first mixed gas expedition on the Andrea Doria organized by Bernie Chowdhury. (Photo courtesy of Michael Menduno)

Over the last quarter of 1992, Skin Diver magazine repeatedly called for an end to deep diving and nitrox use. These editorials sometimes confused nitrox usage with deep diving[2], showing their lack of knowledge about the technology. The Cayman Water Sports Association even warned that divers bent while diving nitrox wouldn’t be treated.

The tek.93 exhibit hall (Photo courtesy of Michael Menduno)

In January, 1993, aquaCORPS organised tek.93, the first annual tech diving conference, in Orlando, Florida, just prior to the annual DEMA show. As a result of the conference, a group of us including Deans and Gurr put together Blueprint for Survival 2.0 – the first set of “best practices” for technical diving that was published that June (1993) in aquaCORPS #6 “Computing.” The 21 recommendations covered training, gas supply, gas mix, decompression, equipment and operations and were based on the 10 principles Exley developed from a thorough analysis of cave diving accidents (Basic cave Diving: A Blueprint for Survival) which helped reduce fatalities. We also started Incident Reports, a popular new section featuring detailed analyses of tech diving accidents.

1993: aquaCORPS Journal organizes the first tek.Conference (TEK.93) for technical divers just prior to the annual Diving Equipment and Marketing Association (DEMA) tradeshow. (photo courtesy of Michael Menduno)
1993: Technical diving pioneer Capt. Billy Deans with Mark Nease and author Michael Menduno in diapers at Key West Diver, the first technical diving training center in the world. Note this was before condom catheters were used. (Photo courtesy of Michael Menduno)

Over the next few years, as tech training agencies developed solid training courses and safety records improved, technical diving began to establish itself as a legitimate branch of sport diving, and mix technology such as nitrox was gradually adopted by the recreational side of the diving business.[3] By 1995, PADI along with the British Sub-Aqua Club (BSAC), National Academy of Scuba Educators (NASE) and Scuba Schools of America (SSA), joined other recreational and technical diving training agencies to offer enriched air nitrox training. The era of single mix technology, i.e. air diving, was dead.

The establishment of tech diving and nitrox use helped fuel the development of a mixed gas infrastructure at the retail dive store level, a necessary step for the emergence of rebreather technology.

Thirdly, it was clear that training requirements for rebreather diving were significant. But semi-closed rebreathers were likely to be the first adopted by sport divers because of their relative simplicity and lower cost. Unlike nitrox, there were few concerns about the technology. We continued to offer rebreather workshops and “try-dives” hosted by manufacturers at our annual tek conference, however product was slow to materialise.

Bring on The Breathers!

Viewed as the ultimate in self-contained diving technology and the future of tech diving, rebreathers could greatly extend bottom times independent of depth, while providing near optimal decompression in a small package. However, as it wasn’t readily available, we didn’t how much discipline and attentiveness were required for rebreather diving.

We started reporting on rebreathers in June 1990. Over the next few years, rebreathers articles increased in our issues. We also featured several rebreather sessions at tek93.

It was clear there were many myths and misunderstandings surrounding rebreathers at that time. Few in the sport diving community owned a rebreather, so I teamed up with Robinette, who had built the ShadowPac rebreather in the 1970s, to organise the first Rebreather Forum at Key West, Florida, in May 1994. We featured special guests Dr. Ed Thalmann, the U.S. Navy’s diving physiology guru who oversaw the development of the Navy’s mixed gas decompression tables, and inventor Alan Krasberg – arguably the grandfather of mixed gas closed circuit rebreathers.

That first Forum had 90 attendees, including five rebreather manufacturers, numerous training agencies and representatives from sport, trainers from the military and commercial diving communities. It was the first time such a group had been assembled.

The findings from the forum were several-fold. Firstly, there was clearly a market for rebreathers but nobody could get one. Secondly, the military, through strict discipline and massive support, was the only diving community successfully using rebreather technology but those two conditions weren’t easily found in sport diving. Commercial divers rejected rebreathers for its complexity and unreliablility.[4] Thalmann cautioned during the forum about the very real problems with rebreathers potentially causing fatalities to ill-prepared divers compared to the proven reliability of the scuba regulator.

Rebreather Forum 2.0

In 1995, Dräger, who had been building rebreathers since the 1940s, launched the Atlantis, a semi-closed unit rebreather designed for recreational divers. With such an established manufacturer in the sport market, sport diving rebreathers gained great credibility. In Japan, Grand Bleu began selling the Fieno, a semi-closed unit. However, although the tech diving community was booming, it seemed likely that rebreathers were going to be adopted by the recreational community before tech divers.

In September 1996, Robinette and I organised Rebreather Forum 2.0 in Redondo Beach, California with PADI publishing the forum’s proceedings through their Diving Science & Technology (DSAT) subsidiary. Although there were more than 100 attendees along with 15 rebreather manufacturers, only five are building rebreathers today.

1996: Ambient Pressure Diving’s managing partner Martin Parker wearing an Inspiration rebreather prototype (Photo courtesy of Michael Menduno)

At the time, the U.S. and British navies were the largest users of mixed gas rebreathers, with 240 units in service out of a total of 600 in inventory. There were at most 25-50 units in the tech community. Most of these belonged to small groups like Stone‘s team, boutique manufacturers such as Steam Machines and explorers and filmmakers.

The conclusions from the forum were manifold: Although there was universal interest and everyone knew the risks, no one was worried rebreathers could be problematic for sport divers. The thinking was that semi-closed systems such as the Dräger units would be more suitable for sport divers even though they had no rebreather experience.

Although technical training agencies actively promoted rebreather instructor courses, there was no standardised training yet. The sport diving community had no supporting infrastructure like the military’s, nor any retail support. They were starting from scratch.

With regards to decompression, the only validated constant partial pressure of oxygen (PPO2) tables at the time were the US Navy 0.7 atm constant PPO2 for nitrox and heliox rebreather diving. Note that a closed circuit rebreather is designed to maintain a constant PPO2, called a “set point” throughout the dive. It was unknown at the time, if simply reprogramming a dive computer to calculate decompression based on the oxygen levels supplied by a rebreather would work effectively.

The Forum also noted that the development of on-board CO2 monitors could greatly improve diver safety, and the community was advised to adopt a maximum constant PPO2 of 1.3 atm similar to the U.S. Navy. Dr. Bill and others argued that a diver’s PPO2 should be kept at 1.4 atm during the dive and boosted to 1.6 atm for decompression, which eventually became the standard.

Safety was viewed as the biggest challenge in adopting rebreathers for sport diving. Deans hoped “the challenge to bring the technology to market” wouldn’t kill too many divers.

It would be another decade before rebreathers became common tools among technical divers. Unfortunately, Deans was correct about the challenge. There were 200 reported rebreather fatalities worldwide between 1998 and 2012 when Rebreather Forum 3 was held. There were about 10 fatalities a year from 1998-2005, and an average of 20 a year from 2006-2012. By comparison, there are about 100-120 scuba diving fatalities a year in the U.S., Canada, U.K. and Europe combined – the majority of the worldwide market.

Later in 2012, Dr. Andrew Fock, head of hyperbaric medicine at The Albert Hospital in Melbourne, Australia, estimated that rebreather diving was likely five to 10 times as risky as open circuit scuba diving, accounting for about four to five deaths per 100,000 dives, compared to about 0.4 to 0.5 deaths per 100,000 dives for open circuit scuba. This makes rebreather diving riskier than sky diving at .99 deaths/100k, but far less risky than base-jumping at 43 deaths/100k. Since 2012, the evidence suggests that rebreather diving safety has continued to improve.

You’ve Come Along way Baby

Despite controversy and initial high incident rates, technical diving significantly improved its safety record and has found its stride. As Dr. Bill suggested in his prescient article, Call It High Tech Diving, that ran in that first issue of aquaCORPS: “With all these warnings issued, and all the described parameters met, advanced high-tech diving offers the prepared knowledgeable diver a chance to experience a realm not previously accessible to humans. And there is every reason to think—as our technology and knowledge advance—that we will be able to push the envelope even farther,” he wrote.

And we did.

[1] Lad Handelman, co-founder of Oceaneering told me that before mixed gas diving, commercial air dives were limited to about an hour or less bottom time at 250 ft/76m. Note the nitrogen in air (21% oxygen, 78% nitrogen, 1% trace gases) becomes increasingly narcotic beyond about 4 atm or 100 ft/30m, and divers are at risk of CNS oxygen toxicity beyond about 187 ft/57m.

[2] Nitrox is typically used as a bottom gas on relatively shallow dives (less than 130ft/40m), and also used by technical divers as a decompression gas following deep helium dives.

[3] Bret Gilliam and Mitch Skaggs formed Technical Diving International (TDI) in 1994 after splitting from IANTD, which went on to become the largest tech training agency. In 1998, Jarrod Jablonski and Todd Kincaid formed Global Underwater Explorers (GUE).

[4] Rebreathers are now used in the North Sea as a diver bailout device as part of contractor’s saturation diving systems.

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