Connect with us


RF4 Consensus Statements

One of the deliverables of Rebreather Forum 4 was a set of “consensus statements” that reflected the views of participants on issues deemed important to the Forum. The statements, published here, were crafted by Drs. Simon Mitchell and Neal Pollock based on the presentations and discussed and voted by delegates through a democratic process. The statements will be included in the RF4 Proceedings along with an edited version of the discussions surrounding each statement



by Drs. Simon J. Mitchell and Neal W. Pollock. Images by Jason Brown, BARDOPhotographic unless noted.

Dr. Simon Mitchell explaining the consensus statement process.

Following the precedent set in Rebreather Forum 3 the final half day of the 2023 meeting was dedicated to discussion of a series of consensus statements intended to reflect widely supported opinions of participants. The statements were drafted by the authors during the course of the meeting, and were explicitly designed to be confluent with important messages emerging from presentations and any subsequent discussion. The statements do not purport to be the only important messages to emerge from the forum; the authors focused on matters that seemed important, widely supported and relatively non-controversial, and that would therefore lend themselves to meaningful consensus. 

The statements were presented one by one to a plenary session of participants and discussion was invited. The amount of discussion was variable with some statements attracting little, and others requiring more debate and wordsmithing which was performed live. As is the case with sessions of this nature some degree of directive chairmanship was required in order to work through the list of statements within the allocated time. For this reason discussion of some statements had to be truncated but there was substantial discussion of all statements that emerged as controversial for any reason. For transparency, a transcript of the discussion will be presented in the forum proceedings (edited to correct grammar and eliminate extraneous comments, but retaining the spirit and intent of the original dialogue). At the end of discussion of each statement a show of hands was taken to gauge agreement and disagreement with the statement. It was announced prospectively that a clear majority of participants would need to agree for a statement to make the published list. Ultimately, after discussion and rewording where necessary all draft statements were accepted; most unanimously and never with more than 5-10% in disagreement. 

The 28 statements are presented in thematic areas designated “safety,” “research,” “operational issues,” “education and training,” and “engineering.” The authors acknowledge that some of these statements seem relevant to multiple themes. Most are self-explanatory, but some are accompanied by contextualizing narrative from the authors where necessary. 

Drs. Neal Pollock and Simon Mitchell noting key points while keeping the RF4 program on track. Photo by Peter Symes.

Thematic Area “Safety”

Accident Data

Analysis of contemporary rebreather accident data indicates a continued need for integrated effort to reduce the rates of injury, morbidity, and mortality associated with rebreather diving.

Cardiac Health Surveillance

The forum endorses the principle of periodic cardiac health surveillance for all rebreather divers with an emphasis on targeted annual or biennial evaluation for divers older than 45 years even in apparent good health.

Contextualizing narrative: the forum resolved that this statement should be accompanied by citation of relevant supportive medical literature. Various studies have identified the importance of cardiac events as the disabling injury in recreational diving fatalities,2,3 and an expert consensus guideline for cardiac evaluation of divers was recently published.4

Accident Analysis

The analysis of accident, incident, and injury data from rebreather incidents should consider wider contextual elements and error-producing conditions and not just immediate contributory factors.

Solo Diving

The forum recognizes that solo diving may increase the likelihood of a fatality in the event of a rebreather diving incident.

Pre-Entry Checklists

The forum strongly advocates the use of a pre-entry checklist (in a check and response format if practicable) administered just prior to water entry. This should be a brief checklist addressing contextually relevant critical safety items such as “rebreather switched on,” “oxygen cylinder on,” “diluent cylinder on,” “wing/buoyancy device/drysuit inflation connected and working.”

A lighter moment, one of several, during the nearly five hours of consensus building sessions.

Thematic Area “Research”

Training and Sales Data

The forum strongly endorses continued collection of anonymized rebreather diver training and rebreather unit sales data by the Divers Alert Network Research Department as an adjunct to interpreting diver accident statistics.

Mishap and Near-Miss Reporting

The forum advocates self-reporting of diving mishaps and near-misses, and reporting of fatalities, to the DAN diving incident reporting system.

Contextualizing narrative: The DAN diving incident reporting system was nominated in this statement because of its high visibility, global scope, and accessibility for divers anywhere in the world. However, the forum also acknowledged the value of national or regional systems of relevant data collection and analysis (such as that run by the British Sub-Aqua Club [BSAC]) and also advocates for maintenance of diver reporting to such systems. Data sharing between DAN and regional groups was also discussed and was supported. 

End-Tidal CO2 Monitoring

The forum identifies as a research priority/goal the development of capnography and accurate end-tidal CO2 monitoring for rebreathers.

Regenerating CO2 Absorption Technology

The forum identifies as a research priority the development of regenerating CO2 absorption technologies.

Full-Face Masks

In relation to a documented RF3 research priority, the forum recognizes the emergence of data pertaining to the efficacy of full-face masks in preventing water aspiration in unconscious subjects.5 This strengthens the argument for considering their use in scenarios associated with an elevated risk of oxygen toxicity such as in-water recompression.

Real-Time Physiological Monitoring

The forum endorses ongoing research into strategies for real-time diver physiological monitoring.

Charlie Roberson, founder of Fathom Dive Systems offering a comment.

Thematic Area “Operational Issues”

Bailout Rebreathers

The forum identifies as a priority/goal the development and documentation of practices and/or monitoring for optimizing bailout rebreather use.

Mouthpiece Retaining Straps

The forum recognizes the use of correctly deployed mouthpiece retaining straps as a strategy for avoiding loss of the mouthpiece and minimization of water aspiration in the event of loss of consciousness underwater.

Bailout Valves

The forum recognizes the potential advantage of a bailout valve for transitioning from closed- to open-circuit in the event of hypercapnia or other events requiring bailout; this advantage requires a high performance open-circuit breathing system.

Mixed Mode Diving

The forum recognizes mixed mode diving as a legitimate buddy option in dives of appropriate scope but recommends a mixed mode briefing, and pre-establishment of strategies for gas sharing.

Contextualizing narrative: ‘Mixed mode’ in this context refers to divers using different underwater breathing apparatus types working as a buddy pair, for example, and open-circuit diver diving with a rebreather diver.

Mixed Platform Diving

The forum recognizes mixed platform diving as a legitimate buddy option and recommends at least a mixed platform briefing with emphasis on emergency procedures.

Contextualizing narrative: ‘Mixed platform’ in this context refers to divers using different brands or models of the same underwater breathing apparatus type working as a buddy pair, for example, two divers using different brands of rebreather.

Asymmetric Equipment

The forum recognizes symmetric (same rebreather unit) or asymmetric (different rebreather unit) multiple rebreather systems as options for an alternative breathing or bailout system.

Contextualizing narrative: ‘Symmetric’ in this context refers to multiple rebreathers of the same make and type, and ‘asymmetric’ refers to multiple rebreathers of different makes or types.

Head-up Display

The forum recommends the display of safety-critical information such as loop oxygen status on a head-up display.

Standard Operating Procedures and Emergency Action Plan Documentation

The forum endorses the compilation of a contextually tailored and detailed dive plan/standard operating procedures document and emergency action plan prior to rebreather diving expeditions.

Emergency Preparedness

The forum endorses the importance of emergency preparedness including a validated emergency action plan, oxygen supplies, access to appropriate medical support with adequate medical supplies, and evacuation plans during rebreather diving expeditions; particularly to remote locations.

In-Water Recompression

The forum recognizes the recent medical endorsement of emergency in-water recompression of selected divers by appropriately equipped teams trained in oxygen decompression.6,7

DAN Europe Senior Vice President Laura Marroni with a question for Dr. Mitchell and the delegation.

Thematic Area “Education and Training”

Manufacturer-Training Agency Coordination

The forum recognizes the challenges for training agencies in maintaining confluence between course content/availability and emergence of new rebreather technologies. The forum endorses close liaison between training agencies and manufacturers (including factory trainers) to share information about emerging technologies and manufacturer expectations on training approaches using their platforms. 

Knowledge Gap Targets

The forum identifies the following as common knowledge gaps that constitute educational opportunities for rebreather instructors and leaders to address: 

  • Predispositions, symptoms, and frequency of immersion pulmonary edema 
  • Increasing risk of deeper dives executed perfectly on the same decompression algorithm (ie, not iso-risk exposures)
  • Scope of variability in venous gas emboli counts in individual divers serially performing identical dives and the associated implications for interpretation of individual monitoring of venous gas emboli post-dive
  • The difference between CO2 inhalation and hypoventilation as the two mechanisms of hypercapnia in rebreather diving.
  • Correct management of ingestion/inhalation of caustic scrubber byproduct (ie, ‘caustic cocktail’)
  • Function of CO2 scrubbers

Contextualizing narrative: It is emphasized that this list is not intended to define all relevant knowledge gaps. Rather, it contains items that emerged as obvious educational opportunities in the various presentations and discussion at Rebreather Forum 4.

Diver Retraining/Updating

The forum recognizes the potential for skill and knowledge degradation over time or during periods of diving inactivity and encourages training agency initiatives to promote continuing education and training, refresher options, and/or recertification as appropriate.

Gavin Anthony,, principal of Life-Support and Diving GAVINS Ltd emphasizing a point.

Thematic Area “Engineering”

Oxygen Sensor Replacement Warning

The forum recommends that manufacturer’s consider incorporating oxygen sensor replacement warnings in rebreather operating systems 

Contextualizing narrative: The context in which this discussion took place was that these warnings would be based on elapsed time since sensor manufacture. 

Gas Density Display

The forum recommends that rebreather manufacturers consider incorporating gas density displays and/or alarms in the user interface.

Contextualizing narrative: The discussion around this statement included strong advocacy for viewing gas density as a dive planning and operational concern that requires careful consideration.

Orientation Monitoring

The forum identifies optimally positioned accelerometers or inclinometers with rebreathers as an opportunity for capturing diver trim and movement data that could be used for training, performance, and forensic evaluation.

Inspired CO2 Monitoring

The forum recognizes the potential safety advantage of inhale side CO2 or scrubber monitors, but acknowledges that they may fail to detect some causes of hypercapnia.


  1. Mitchell SJ. Rebreather Forum 3 consensus. In: Vann RD, Denoble PJ, Pollock NW, eds. Rebreather Forum 3 Proceedings. Durham NC: AAUS/DAN/PADI;2014. p. 287–302.
  2. Lippmann J, Taylor DM. Scuba diving fatalities in Australia 2001 to 2013: chain of events. Diving Hyperb Med. 2020;50(3):220–229.
  3. Denoble PJ, Caruso JL, Dear Gd, Pieper CF, Vann RD. Common causes of open-circuit recreational diving fatalities. Undersea Hyperb Med. 2008; 35(6):393–406.
  4. Jepson N, Rienks R, Smart D, Bennett MH, Mitchell SJ, Turner M. South Pacific Underwater Medicine Society guidelines for cardiovascular risk assessment of divers. Diving Hyperb Med. 2020;50(3):273–277.
  5. van Waart H, Harris RJ, Gant N, Vrijdag XCE, Challen CJ, Lawthaweesawat C, Mitchell SJ. Deep anaesthesia: the Thailand cave rescue and its implications for management of the unconscious diver underwater. Diving Hyperb Med. 2020;50(2):121–129.
  6. Mitchell SJ, Bennett MH, Bryson P, Butler FK, Doolette DJ, Holm JR, Kot J, Lafere P. Pre-hospital management of decompression illness: expert review of key principles and controversies. Diving Hyperb Med. 2018;48(1):45–55.
  7. Doolette DJ, Mitchell SJ. In-water recompression. Diving Hyperb Med. 2018;48(2):84–95.


Rebreather Forum 3.0 Consensus Statements (2012)

Rebreather Forum 2.0 Findings & Recommendations (1996)

Simon Mitchell, MB ChB, PhD, FANZCA Simon works as an anaesthesiologist and diving physician, and is Professor of Anaesthesiology at the University of Auckland. He is widely published in diving medicine and physiology. Simon has a long career in sport, scientific, commercial, and military diving. He is an active technical diver and was first to dive and identify three historically significant deep shipwrecks in Australia and New Zealand, including one in 2002 which was the deepest wreck dive undertaken at the time. He was conferred Fellowship of the Explorers’ Club of New York in 2006, and was the DAN Rolex Diver of the Year in 2015.

Neal W. Pollock, PhD Neal Pollock holds a Research Chair in Hyperbaric and Diving Medicine and is an Associate Professor in Kinesiology at Université Laval in Québec, Canada. He was previously Research Director at Divers Alert Network (DAN) in Durham, North Carolina. His academic training is in zoology, exercise physiology and environmental physiology. His research interests focus on human health and safety in extreme environments. He is an emeritus editor-in-chief of the journal Wilderness & Environmental Medicine. He began open-circuit diving in 1979, and closed-circuit diving in 2002.


The Aftermath Of Love: Don Shirley and Dave Shaw

Our young Italian poet-explorer Andrea Murdoch Alpini makes a pilgrimage to visit cave explorer Don Shirley at the legendary Bushmansgat cave in South Africa. In addition to guiding the author through the cave, Shirley and Alpini dive into history and the memories of the tragic loss in 2005 of Shirley’s dive buddy David Shaw, who died while trying to recover the body of a lost diver at 270 m/882 ft. The story features Alpini’s short documentary, “Komati Springs: The Aftermath of Love.”




Text by Andrea Murdock Alpini

Inside the Black Box of Boesmansgat’s dive archive (Dave Shaw memorabilia)

🎶 Pre-dive clicklist: Where is My Mind by Pixies🎶

South Africa, Komati Springs.

On October 28, 2004, two cave divers and long-time friends, Don Shirley and David Shaw, planned a dive at Boesmansgat (also known in English as “Bushman’s Hole”) a deep, submerged freshwater cave (or sinkhole) in the Northern Cape province of South Africa. Dave dove to 280 meters, touched the bottom and started exploring. At that time, Shaw had recently broken four records at one time: depth on a rebreather, depth in a cave on a rebreather, depth at altitude on a rebreather, and depth running a line. While on the dive at Boesmansgat, he found a body that had been there for nearly ten years, 20-year-old diver Deon Dreyer. 

After obtaining permission to retrieve the body from Dreyer’s parents, the two friends returned three months later. They enrolled eight support rebreather divers (all of whom were close to Don) and Gordon Hiles, a cameraman from Cape Town, who filmed the entire process—from the preparation on the surface to the operation at the bottom of the cave. The surface marshal was Verna van Schaik, who held the women’s world record for depth at the time. Little did they know that Dave would not come back from his 333rd dive, one that he himself recorded with an underwater camera. 

Researchers have determined that while attempting the retrieval, Dave ran into physical difficulties with the lines from the body bag and the wires from the light head. The physical effort of trying to free himself led to his death for what is believed to be respiratory insufficiency (see video below). Don Shirley nearly died as well, and apparently was left with permanent damage that has impaired his balance. 

Nearly 20 years later, our own Andrea Murdock Alpini visits Don and has this to say: 

Dave and Don before a dive.

February 2023—I arrive at the mine owned by cave expert and pioneer of deep diving, Don Shirley. The place is fantastic—the wild nature, the warm water, and the dives are amazing. Every day I spend at least 230 minutes underwater, filming the mines and what is left of man’s influence in this beautiful and God-forgotten corner of Africa. Every day I have time to talk, plan dives, and prepare the blends together with Don Shirley. 

The following is a part of the story that links Don Shirley to South Africa. Stories and places intertwine between Komati Springs, Boesmansgat (or “Bushman’s Hole”) and then the fatal dive with his friend Dave Shaw. 

Monkeys arrive on time every 12 hours. They showed up last night at about 5:00. They came down from the trees in large groups. They start playing, throwing themselves from one branch to another, chasing each other. Mothers hug their little ones. Some of them play with oxygen cylinders, the smaller ones instead with methane gas tanks, the ones we use for cooking. We are surrounded by gas blenders of all kinds. 

A herdsman’s hat rests on the workbench. Two hands with delicate, thin skin take adapters, cylinders, and whips.They open and close taps. Notebooks report all the consumption for each charge, strictly written in liters with the utmost precision. Impressions: An Amaranth t-shirt, an unmistakable logo, that of the IANTD. A pair of jeans and then some boots. He has a slight physique, he is lean and athletic with a beard that is white now, and a few days’ old. 

While he works carefully, I do not disturb him, for I know well that when mixing, one is not to be interrupted, at least this is so for anyone who loves precision. Then, when he’s done, we have time to talk a little bit together.

Don Shirley with the author planning a dive at Komati Springs

We sit at his desk and then go to the board to plan the dive in the mine.

Don shows me the map of the first level. He explains some important facts to me, then his hands pull out a second sheet with the plan redesigned from memory of the second level at 24 m/70 ft deep. “This is the guitar level,” he says. 

At first I don’t understand. He chuckles. I look at the shape he drew and, yes, that floor plan is a cross between a Fender Stratocaster and a Picasso guitar. Anyway, it’s a guitar, no doubt.

We begin planning the dive together. It’s exciting to hear him talk; he speaks in a soft, elegant tone, and it moves me. I look at his index finger moving. I listen to his words, but I also look at his eyes. 

He gives me some advice but also tells me, “This mine is more similar to a cave. I have left it as it is. I want people to explore it and not follow any lines.”

Freedom of thought, plurality of choices. Acceptance of risk, inclusion of the other in what belongs to you. It’s clear that Don’s vision of diving is uncommon. Freedom is beautiful, but it is the most dangerous thing there is, if mishandled. 

An old map of Komati’s mine site

The next day, we have an appointment at 7 o’clock at the lake. Before diving this morning, we saw where the “Tunnel of Love” originates on the surface, a curious gallery which I came across underwater. There are two parts of the mine that survived the destruction of the mining facility after its closure. One of these is the tunnel where we are going, the other part is perched in the middle of the mountain.

Don explains that the tunnel is now frequented by the wild animals who go to drink there, so we follow their trail. The water has flooded everything up to just a few meters below the surface of the bush. Don cuts the underbrush that makes the path difficult. He wears his faithful herdsman’s hat and never takes it off. The ground begins to tilt slightly, a good sign that we are about to arrive. A series of stones suggest that here the path has been paved. “It was covered in wood,” Don explains.

The path that started from the building where the miners lived is now demolished. Following it, we arrive at what was called “The Tunnel of Love.”

The tunnel that was the mine’s main entry point. Narrow and difficult, the tunnel led to level one—now underwater at a depth of 18 m/60 ft.

We turn on the headlamps and enter. A small colony of bats flaps its wings upon our arrival. The water touches our boots. Some roots filter from the rock and stretch to the resurgence. The scenery is evocative.

The author and Marco Setti in the end of their explorations at Komati Springs

Don kneels, peering at the water, and something. He looks at the water and something changes within him. Something has changed in our shared dialogue.

It’s as if Don takes on another language as he speaks. He always looks straight ahead. His vocabulary changes, and with it his tone of voice. We talk about politics, economics, the future of Komati Springs, the origin of the name of the place, the history of the mine, but we never mention two topics: diving and Dave Shaw.

Don’s a real caveman. I know that those who love caves are not ordinary people. We who do are a little bit mad to do what we do and love, but he’s different. He is comfortable here; he has found his dimension.

I remember asking him a question when we were inside the Tunnel of Love, breaking one of the long silences: “What thoughts are going through your mind?” He seemed to have reached a meditative state, a kind of catharsis. He replied, “I am just relaxing. This is a peaceful place. “

Around nine o’clock, we travel again to the lake, leaving the dry caves behind. 

Exploring a tunnel in the flooded mine.

The first dive lasted 135 minutes, the second 95 minutes. Once the equipment is set up, I return to the cottage to dry everything and recharge the cylinders.

Don’s hands this time are again without gloves. Before we start mixing, we walk into his office.The walls are lined with articles he has published over the years. 

He shows me the medals for valor he got when he was on duty in the British Army. When we return to a small corridor that acts as a barrier, my eyes fall on two photographs. “Is that Dave?” I ask. “That’s him. We were here in Komati,” Don tells me. “You see? This is his hat,” and he points to what is on his head.

The pond above the mine and wild nature who surrounds Komati. A real wild South Africa scenario.

The Consequences of Love

These are the consequences of love, I think. A friendship that transcends time, life, but also death.

It’s time to prepare the blends for tomorrow. As the oxygen pumps out, Don asks me, “Have you ever seen our Boesmasgat’s diving slates?” Obviously, I had never seen the decompression tables of that famous and tragic dive to 280 m/920 ft depth at 1,600 meters (nearly 5,000 feet) altitude.

“Hang on a sec.” Don picks up a small black box with a yellow label and brings it to me. He opens it. “These are the original dive charts. These are mine; these are Dave’s.” The box also contains the famous blackboard with the inscription, (“DAVE NOT COMING BACK”) from the documentary, as well as a pair of underwater gloves used in that dive, and then the heirloom of his CCR computer that broke due to excessive hydrostatic pressure.

He exits the room. He leaves me with those emotionally charged objects in my hands. I can’t see them any differently. They obviously have historical value; but, for me, the human sense prevails. I look at the decompression tables, touch the gloves, and think about the hands that wore them, that read the various whiteboards, and I imagine the scenes of that time.

Early days of explorations at Komati Springs, Don Shirley with Dave Shown and their team 
Don Shirley wearing Dave’s old hat while scouting out the Tunnel of Love

I place everything back in the box. I hand it to Don as I would hand him a precious urn. In part, it is one. I find it hard to express myself in that moment. He understands why.

At this point I ask him, “What was the true meaning of that extreme dive that Dave wanted to do? Why did he do it?”

“He just wanted to explore the bottom of that cave,” Don said. “Wherever Dave went, he wanted to get to the bottom. That’s how we’ve always done it together. So that’s what we did here at the mine.” 

Don then tells me a series of details and information about that place, about the geological stratification of the cave; he talks a little about the owner of the land where the famous sinkhole is located, and finally he talks about many other aspects of their failed dive. I promised to keep it to myself, and I will do so, forever.

Such is a connection that endures over time.


Wikipedia: Dave Shaw

YouTube: Diver Records Doom | Last Moments-Dave Shaw

Wikipedia: Dave Not Coming Back (2020) A critically acclaimed film that centers on diver Dave Shaw’s death while attempting to recover the body of Deon Dreyer from the submerged Boesmansgat cave in 2005.

Shock Ya: Don Shirley Fondly Remembers Scuba Diving with David Shaw in Dave Not Coming Back Exclusive Clip

Outside: Raising the Dead (2005) by Tim Zimmerman

Other stories by the prolific Andrea Alpini Murdock:

InDEPTH: Finessing the Grande Dame of the Abyss

InDEPTH: Hal Watts: Plan Your Dive

InDEPTH: I See A Darkness: A Descent Into Germany’s Felicitas MineInDEPTH: Stefano Carletti: The Man Who Immortalized The Wreck of the Andrea Doria

Andrea Murdock Alpini is a TDI and PSAI technical trimix and advanced wreck-overhead instructor based in Italy. He is fascinated by deep wrecks, historical research, decompression studies, caves, filming, and writing. He holds a Master’s degree in Architecture and an MBA in Economics for The Arts. Andrea is also the founder of PHY Diving Equipment. His life revolves around teaching open circuit scuba diving, conducting expeditions, developing gear, and writing essays about his philosophy of wreck and cave diving. He published his first book, Deep Blue: storie di relitti e luoghi insoliti (2018) and IMMERSIONI SELVAGGE, published in the Fall of 2022.

Continue Reading

Thank You to Our Sponsors

  • Fathom


Education, Conservation, and Exploration articles for the diving obsessed. Subscribe to our monthly blog and get our latest stories and content delivered to your inbox every Thursday.

Latest Features