Revealed at RF4: rebreathers by the numbers

Rebreather try-dives at RF4 (RF4 / Jason Brown -
Rebreather try-dives at RF4 (RF4 / Jason Brown -

How many closed-circuit rebreathers are out there, how many divers are certified to use them and who are those users in terms of age, gender and experience? New statistics were revealed at Rebreather Forum 4, the industry symposium and scientific meeting held recently in Malta, in what was claimed to be the most comprehensive data-analysis of the market to date. 

The three-day meeting in Valletta from 20-22 April brought together 294 international dive professionals and CCR specialists for presentations, discussions and, either side of the talks, scuba diving. It was the first time a Rebreather Forum had been held outside the USA.

Also read: Triple-CCR diver dies on 100m solo dive

“RF4 was eye-opening,” says organiser Michael Menduno. “We not only had the most comprehensive data on rebreather adoption and training to date, but it’s changed a lot of people’s perspective on where we are at with regards to the technology.” 

Rebreather Forum 4 organiser Michael Menduno (RF4 / Jason Brown -
RF4 organiser Michael Menduno (RF4 / Jason Brown –

The stated aim of RF4 was to advance and consolidate the diving community’s knowledge of CCR technology and its use by technical, government and scientific divers, with the goal of improving rebreather diving safety and performance. 

However, the data-crunching revealed what many had suspected – that CCR safety remained as pressing a concern as it had at RF3 in Orlando in 2012. “We still have more work to do with regards to diver safety,” says Menduno.

With that in mind, a series of “consensus statements” were agreed among RF4 participants on safety, research, education and training, engineering and operational considerations. Intended to guide change and set safety priorities for the industry, these will be published later this year.

The statistics

RF4 presentation at the University of Valletta (RF4 / Jason Brown -
RF4 presentation at the University of Valletta (RF4 / Jason Brown –

Statistical insights based on analysing data from Divers Alert Network, public surveys and CCR manufacturers were revealed at RF4 by DAN research director Dr Frauke Tillmans.

According to information provided by 20 of 24 recreational CCR manufacturers, she was able to estimate that between 25,000 and 35,000 rebreather units are out there today. The divers who use them have a mean age of 42-46, are 84-95% male and have been certified for an average of six years, she said, based on data from the DAN hotline, RF4 participants and a related survey.

CCR certifications had ranged between 3,500 and 5,200 a year since RF3, with 2023 looking set to be the strongest year to date, according to analysis by DP Research Solutions. This was based on certifications at all levels submitted by training agencies BSAC, Dive RAID, FFESSM, GUE, IANTD, PADI, SDI/TDI and SSI.

On the downside, Dr Tillmans estimated that rebreather divers were dying at a rate of 2-4 per 100,000 dives. This conclusion was in line with analysis by Dr Andrew Fock at RF3 that had put the estimated risk of dying on a rebreather at 5-10 times higher than that on open-circuit scuba – indicating that diver safety had not improved in the intervening 11 years.

More than 241 rebreather divers were reported to have died since RF3.

Richard Harris presentation at the closing dinner (RF4 / Jason Brown -
Richard Harris presentation at the closing dinner (RF4 / Jason Brown –

RF4 featured 22 presentations from experts including keynote speaker Dr Richard “Harry” Harris, who this year completed the first reported CCR dive with hydrogen as a diluent, and prominent dive-science researchers. All the presentations will eventually be made available online.

A total of 111 rebreather try-dives were conducted at Malta’s National Pool Complex before the conference, with divers sampling units including Divesoft Liberty back-mount and side-mount; Lungfish with both standard loop and Alliance full-face mask, Fathom MK III, iQSub XCCR, rEvo, Mares Horizon and M3S Triton, along with Garmin computers and Shearwater and Sonardyne navigation units. 

Divernet carried a pre-forum interview with Michael Menduno about the state of rebreathers in late March.



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