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Bringing Breathers To Antarctica

Thinking about bringing your rebreather on one of Faith Ortins’ Blue Green Expeditions to the Antarctic? What makes you think it will work? John Heine, Diving Safety Officer for the U.S. Antarctic Scientific Program, sought to answer that very question. What he found may surprise you. Just the cold facts, ma’am!

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By Michael Menduno, original paper by Dr. John Heine

Do rebreathers work in ice-cold water, and even colder air at the surface? Those are the questions that research scientist at Jacksonville University Marine Research Institute and veteran diver John Heine sought to answer in a 2016 study funded by the National Science Foundation (NSF), which oversees the U.S. Antarctic Program (USAP), including scientific diving.

“We had an increasing number of queries from researchers that wanted to use rebreathers in the Antarctic,” Heine, who is the Diving Safety Officer for USAP and a member of its Diving Control Board, explained. “The problem is we couldn’t answer the [fundamental] question: will they work or would it be too risky? So, we decided to evaluate a number of rebreathers to see how they performed.” The results of the study were published last year (see foot note 1).

Scientific divers, who operate under an exemption from the Occupational Safety and Health Administration’s (OSHA) commercial diving regulations, have been diving in Antarctica since the 1960s. However, the exemption requires that diving operations be approved by the relevant institution’s Diving Control Board (DCB), in this case USAP’s, which has limited diving to open-circuit scuba. Though there have been a few non-scientific rebreather operations conducted in Antarctica, including the Wes Skiles 2002 Ice Island Project with explorer Jill Heinerth, and a Disney wildlife filming expedition on the Peninsula, these have been poorly documented.

Photo courtesy of Dr. John Heine.

The performance of open-circuit scuba equipment in freezing water is well known. Relevant equipment is regularly tested by the U.S. Navy’s Experimental Diving Unit (NEDU) and within the USAP, and certain regulators, such as the Sherwood Maximus, that perform well in icy conditions, have been approved for use by scientific divers.

Not so for rebreather technology. NEDU presumably has extensive knowledge of the use of rebreathers in cold water—it’s known that Navy Special Forces divers lock out of submarines in arctic waters. However, according to Heine, they won’t(or are unable to) discuss their experience or share data. In fact, as I learned when I did a profile of the NEDU for Alert Diver magazine a few years ago, they don’t even like to acknowledge that sailors dive from submarines.

Putting Rebreathers To The Test

Due to their silence, lack of bubbles, and extended range, an increasing number of scientists have employed rebreathers in their research, albeit in warmer waters, over the last two decades. Not surprising, there are also numerous potential scientific applications for rebreathers in the frigid depths of Antarctica.

These include wildlife behavioral studies, under-ice collections and sampling, and use in the McMurdo Dry Valley lakes to minimize mixing of water layers and adding exhaled gases into the environment. There are also the potential benefits of extending divers’ time and depth underwater, and of course breathing warm, recycled gas as compared to open-circuit scuba.

However, there were many unknowns. Rebreathers are typically tested at temperatures down to 39.2° F /4° C for CE certification. But that’s a big difference with the sub-freezing 28.6° F /-1.8° C water temperatures found in Antarctica, where air temperatures typically average -20° F/-29° C. Heine, who made his first Antarctic dives in 1989, and has subsequently spent 14 seasons on the ice, was concerned about the impact of the cold on the scrubber’s CO2 absorption efficiency, as well as freezing in the loop due to moisture, battery duration and function, display irregularities, accuracy and precision of all readouts and sensors, and potential solenoid and regulator issues.

Photo courtesy of Dr. John Heine.

Heine and his team, which included Dr. Jeffrey Bozanic, author of several books on rebreathers, tested the performance of seven rebreathers, specifically the AP Diving Inspiration, Inner Space Megalodon Legacy and Megalodon 15, the Poseidon Se7en, the Hollis Prism 2 and semi-closed Explorer rebreather (see footnote 2), and Expedition One’s Titan. Their goal was to evaluate the overall performance of regulators, valves, batteries, sensors, and displays both pre-dive and underwater, measure temperatures in different parts of the loop before, during, and after dives, and to evaluate the performance of the rebreathers’ scrubbers. They placed temperature sensors in various portions of the loop to quantitatively measure the temperatures over time.

The Dives

Heine’s five-person dive team conducted a total of 116 no-stop dives to a maximum depth of 130 ft/40 m on the seven rebreathers during the austral summer season in Antarctica (Oct-Nov 2016). The average depth of the dives was 85 ft/27 m, with an average dive time of 33 minutes, for a total of nearly 66 hours. They used air diluent in the rebreathers; low setpoints were 0.5 or 0.7, and the high setpoints were 1.2 or 1.3. Divers were equipped with 40 ft3/5.5 L bailout cylinders, which were also used for drysuit inflation. They also had a safety diver on open-circuit, and surface tender(s).

Dr. John Heine in Antarctica. Heine had his first dives in Antarctica in 1989. He has been going there fourteen seasons now.

The dives were staged from a heated hut, with a temperature of approximately 60° F/15.5° C, and a water temperature of 28.6° F/-1.8° C. The rebreathers were pre-breathed in warm air, either in the dive locker or in the heated hut. Pre-dive checklists were performed on all of the units.

Most dives were conducted in no current and were characterized as “low activity level.” The scrubbers were only used one-half of the manufacturer recommended time (at 4° C) on the advice of Scientist Emeritus and Retired Scientific Director of NEDU Dr. John Clarke, who sits on the USAP Diving Control Board. “Our dives were rarely longer than 40 minutes,” Heine said. “The limiting factor was the cold, and in some cases decompression, not the scrubbers.”

In addition, they performed dry tests where the rebreathers were pre-breathed in a warm shed or in cold ambient air temperatures of 5° F (-15° C) and then left in the cold for a period of two to three hours. Temperature data from the various portions of the loop were recorded and analyzed, along with qualitative observations on the function of the units. “It is eye-opening how fast things freeze up in air,” cautioned Heine, who was first certified in 1976 in Laguna Beach, CA.

The Cold Facts

The good news was that the rebreathers performed better than expected, with the exception of the Hollis Explorer. One hundred eleven dives (96%) were considered “successful,” which was defined as a complete dive without cause for ending or aborting the dive, or switching to bailout. Five dives (4%) required aborting or switching to bailout and ending the dive.

The Se7en, for example, had a few problems with its (galvanic) oxygen sensors; the automatic diluent valve (ADV) on the Inspiration had probable “freeze-ups” on two occasions, and the Explorer had a number of issues with the electronics, including a “bad cell” warning.

These results compare favorably with a 2017 study of open-circuit regulators (see footnote 3). Seventeen models of regulators from 12 different manufacturers were tested in Antarctica and yielded 65 free-flows in 305 dives (21.3%). By comparison, the USAP-authorized Sherwood Maximus regulators had a free-flow rate of only 0.17% during the period of 2007-2017.

The batteries and displays functioned well, except in very cold air temperatures of 5° F/-15° C. In the dry test runs in cold air, scrubber temperatures stayed relatively warm, but temperatures in the lids near the oxygen sensors were below freezing, which is not recommended by the manufacturer. Mouthpieces also froze shut.

In-water evaluations were somewhat mixed. The Megalodon 15 showed temperatures in the lid approaching the ambient water temperature of 28.6° F/-1.8° C, while the inhalation counterlung temperature was about 10° F/5 °C above ambient, suggesting slightly warmed gas being delivered to the diver. In the Prism 2, both counterlung temperatures were near the ambient water temperature, while the temperatures in the lid (near the oxygen sensors) and the central tube of the scrubber remained around 40° F/4.4° C. The exhalation counterlung temperature was right at the ambient water temperature in the Se7en, while the canister temperature was 6-20° F/3-11° C above ambient, similar to results in other rebreather models.

In the Titan rebreather, the scrubber and the lid temperatures remained relatively warm during the dives, while the inhalation hose temperature was close to ambient. In temperate water trials, the inhalation hose temperature was also close to ambient, which suggests that the rebreather was not delivering warmed gas to the diver. The team was not able to measure inhalation gas temperature with the available technology, nor were they able to measure the CO2 in the loop (temperature served as a proxy for absorption efficiency), so these results are unknown.


nspiration shows two dives, top and bottom of scrubber very warm (90 F), and the inhalation and exhalation hose temps. closer to ambient temp.

Poseidon Se7en.  Exhale counterlung at ambient water temp, scrubber canister 5-10 degrees above ambient.

In the Legacy Megalodon, four dives on two consecutive days, with a total scrubber time of 163 minutes.  Axial scrubber temperatures well above ambient, indicating active CO2 scrubbing.

Note that gas temperatures being delivered to the diver in open-circuit systems would most likely be less than the ambient water temperature, due to gas expansion and pressure drop from the second stage pressure of 150 psi above ambient to ambient. So, all CCRs delivered “warmer” gas to the divers compared to open-circuit, but generally not to an appreciable level. Heine believes that adding insulation materials to the canister and breathing loop hoses and/or counterlungs might help in keeping the breathing gas warmer.

As a result of the study, Heine is now incorporating the use of rebreathers into USAP’s diving standards. A first group of rebreather divers from the BBC, who will be filming seals, is expected next season. There will also likely be a project studying diatoms, which grow beneath the ceiling of ice and are easily disturbed by bubbles.

Note: Unfortunately, Global Underwater Explorers (GUE) divers planning to participate in GUE’s 2021 Antarctica Expedition will need to leave their rebreathers at home. The trip will be limited to open-circuit diving only, unlike Heine’s diving scientists.


1. Heine, J.N. and Bozanic, J. 2018. Evaluation of Closed Circuit Rebreathers for the National Science Foundation  US Antarctic Scientific Diving Program Diving for Science 2018: Proceedings of the AAUS 37th Scientific Symposium. 40-58.

2. Huish Outdoors acquired Oceanic and Hollis in 2017 and discontinued the Explorer semi-closed rebreather.

3. Lang, M.A. and J.R. Clarke.  2017. Performance of life support breathing apparatus for under-ice diving operations. Undersea Hyper. Med. 44(4): 299-308.

Additional Resources:

John Clarke Online:

Authorized for Cold Water Service: What Divers Should Know About Extreme Cold: https://johnclarkeonline.com/tag/en-250/

Information on scrubbers and the cold:

Primer on Scrubbers:


Michael Menduno is InDepth’s executive editor and, an award-winning reporter and technologist who has written about diving and diving technology for 30 years. He coined the term “technical diving.” His magazine “aquaCORPS: The Journal for Technical Diving”(1990-1996), helped usher tech diving into mainstream sports diving. He also produced the first Tek, EUROTek, and ASIATek conferences, and organized Rebreather Forums 1.0 and 2.0. Michael received the OZTEKMedia Excellence Award in 2011, the EUROTek Lifetime Achievement Award in 2012 and the TEKDive USA Media Award in 2018.

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Finland’s Newly Established Scientific Diving Academy

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by Edd Stockdale
Header image: Antarctic research as part of Science Under the Ice project Photo by @scienceundertheice.

While exploring the aquatic realm, many divers often encounter objects of interest but are unaware of the historical or scientific value to the fields of archaeology, geology, or biology. Even if they suspect their find might be important, they are untrained in how to treat such a find with an investigative approach.

Scientific diving, separate from sport, recreational, or commercial diving, requires occupational training specific to science-led, underwater activities with the purpose of collecting data and/or samples. This type of diving is important both to research, as well as to policy making, because divers with this specific training and background can make the quantitative or qualitative-based assertions necessary to implement the findings. There is a necessary and important distinction between professional scientific divers and the “citizen science” trained divers who are essential in building public awareness, particularly in conservation projects. 

The necessary training and the regulation of professional scientific diving varies widely from country to country, both in regulation requirements, as well as in practice. In many countries, scientific work is classified as commercial diving, and regulations are set accordingly. At the opposite extreme, underwater scientific activity can be conducted by anyone certified to dive.

Structured approaches were developed to mitigate the abuses that both of these approaches might create—one such approach was specifically from the American Academy of Underwater Sciences, formed in 1977. AAUS, in 1982, received an exemption from commercial diving standards through self-regulation. In Europe, the process of establishing a recognized training standard was slower because many different European countries had different regulations; however, in 2007, after collaborative efforts by leading researchers, the European Scientific Diving Committee was formed. This agency became the European Scientific Diving Panel (ESDP) in 2008. ESDP established the standards for both Advanced European Scientific Diver (AESD) and European Scientific Diver (ESD) that are recognized by its member countries. 

One of the  early members in the establishment of ESDP, Finland, has experienced a decrease in scientific dive training options but no decrease in the demand for trained divers because of the increased amount of marine research and monitoring Finland carries out. To fill this void in suitably trained divers and to develop a new generation of marine researchers, a group of leading representatives from various institutions have successfully sought funding to establish a new, centralized training center—the Finnish Scientific Diving Academy (FSDA) at the University of Helsinki Tvarminne Zoological Station. FSDA is located on the shore of the Baltic Sea. 

Archeologist taking video for photogrammetry model of Garpen by Rikka Tevali, Photo by Finnish Heritage Agency.

The Academy’s primary objective is to train European standard professional scientific dive training for AESD certification, but this is far from its only goal. In addition to the six-week core program, plans are in place for adding dive training to undergraduate and early career research students to stimulate future generations of field-based marine researchers. Courses for divers who want to gain more experience or to develop skills for citizen-science-based projects with shorter timescales are also in the cards, making the Academy a truly centralized base for all aspects of scientific dive activities, one that can offer expertise across the disciplines.

With its location on the Gulf of Finland, this training will predominantly specialize in cold-water based approaches, though training options in other locations are always a possibility to cover different conditions. Taking advantage of the ice conditions in Finnish winter’s polar research dive training, which, combined with easier access and facilities already established, makes the option to train for polar projects—without the logistical hassle of actually getting to research stations in those regions—a realistic possibility. 

Included into the development concept of the FSDA is not only the concentration on classical scientific diving protocols, but also a widening the scope. It is often ironic that all the different areas of diving contain techniques that can overlap to benefit each other but are not taught or communicated; for example, skills used in a cave diving survey could easily benefit an ecological study or archeological field work. Therefore, the coordinator position for the FSDA requires a background in not just scientific, but technical and other areas of diving with the aim to integrate these skills into these areas into the programs.  

As a result, in the future, courses will likely be offered for specific evolving technological options, developing techniques, or specialist subjects that research teams need in order to carry out projects. Training may also be offered for more advanced diving, including mixed gas and rebreathers, to expand the ranges and environments to carry out scientific work. 

At the other end of the spectrum, driven by the growing need for more studies of aquatic regions combined with reduced funds for research, citizen science or the involvement of non-professional volunteers becomes more relevant all the time. 

Training options for divers looking to develop these skills vary dramatically, and they may not be familiar with research institutions where expertise is highly appreciated. 

Due to the need for scientific consistency in work carried out, divers not only need high levels of diving ability, but also an understanding of the project goals that are important for the results to be valid. Such training is specialized, but done and implemented correctly, provides scientists with the resources of capable dive teams, which is one of the long term goals of the FSDA. These programs will also aim to cover more specialized fields of study or the application of different diving procedures, both from the requirements perspective of project leaders looking for teams of “citizen scientists,” as well as from the divers themselves. 



Overall, the creation of the Finnish Scientific Diving Academy is exciting for both the scientific and regular diving communities, as it aims to address reduced access to specialized training while developing newer techniques and raising awareness of the importance of how research into the marine world is carried out, whether it is surveying a 400-year-old shipwreck or the ecology of a reef.

The FSDA has been initially funded by the Antero and Merja Parma Foundation and Weisell Foundation for three years with aims to secure more funding to remain long term and is coordinated by Edd Stockdale. The first courses will begin in April 2022. Queries should be sent to Edd Stockdale


Edd Stockdale has worked in scientific and technical diving for over a decade and joined as Badewanne team member in 2019. He is the coordinator of the newly established Finnish Scientific Diving Academy at the University of Helsinki, which was established to develop scientific diving training to further research abilities and develop new approaches to data collection in cold water based science.  When not working on research diving, Edd can be found exploring the mines and wrecks in the Nordic region or planning the next adventure. He is supported by Divesoft as well as Santi, Halcyon, and REEL Diving in Scandinavia. 

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