At the time, the US and British navies were the largest users of mixed-gas rebreathers, with an installed base of about 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 such as Stone’s team, small boutique manufacturers such as Steam Machines and a few customers, a handful of explorers and film-makers.
At the time of the Forum, Dräger product manager Christian Schultz reported that it had sold about 850 Atlantis semi-closed rebreathers, and we estimated that there might have been as many as 3000 Fienos sold in Japan.
British explorer-engineer Kevin Gurr with his Cis-Lunar Mk 4.
Stone’s company Cis-Lunar Development Labs had also begun selling its MK-IV (fourth generation) rebreather for $15,000.
It would be another year, before Ambient Pressure Diving in the UK launched its Inspiration mixed-gas closed-circuit unit, and the following year when Jetsam Technologies introduced the KISS classic.
The conclusions of Rebreather Forum 2.0 were several-fold. First, there was universal interest in rebreathers. Unlike nitrox, there was no opposition.
No one was worried that rebreathers could be problematic for the sport-diving community, although it was recognised that rebreathers were far more complex than open-circuit scuba and had insidious risks.
Again, the thinking was that semi-closed systems such as the Dräger units might be more suitable for sports divers. It was also clear that the sport-diving community had no appreciable experience with rebreathers.
Martin Parker, MD of Britain’s AP Diving, with a prototype of the first production closed-circuit sport rebreather, the Inspiration; WKPPcave-diver George Irvine with an early Halcyon PVR-BASC aka ‘The Fridge’ semi-closed rebreather; Leigh Bishop preparing to dive in 1993.
Though the technical training agencies were actively promoting rebreather instructor courses, there was no standardised training yet. Training agencies were urged to work closely with manufacturers to develop sound training courses, which emphasised proper responses to failure modes.
The forum recommended that instructors own, or have on-demand, access to the units on which they planned to train divers. At that time, agencies were selling rebreather instructor certifications, but the instructor didn’t have to own a unit or have that much experience.
It was also recognised that the sport-diving community did not have a supporting infrastructure like the military’s, nor any retail support at that time. In other words, the community would be starting from scratch.
With regards to decompression, the only validated constant partial pressure of oxygen (PO2) tables at the time were the US Navy 0.7atm constant PO2 for nitrox and heliox rebreather diving.
Note that a closed-circuit rebreather is designed to maintain a constant PO2, called a “set point,” throughout the dive.
It was unknown at the time whether simply reprogramming a dive-computer to calculate decompression based on the oxygen levels supplied by a rebreather would work effectively.
The forum asserted that third-party pre-market rebreather testing was critical to ensure reliable and high-quality products. It also concluded that the use of full-face masks and/or mouthpiece retaining straps, which were standard in military diving, and adherence to the buddy system could improve safety.
In addition, the forum noted that the development of on-board CO2 monitors, which didn’t exist at the time, could greatly improve diver safety, and the community was advised to adopt
a maximum constant PO2 of 1.3atm, similar to the US Navy.