An RB can kill you plenty dead well within recreational limits. A good friend of mine, Paul Blanchette, who had extesive experience deeper than 300 feet, died on the wreck of the Chester Poling early this summer.
The incident was ultimately found to be caused by diver error, despite the fact that Paul was one of the most meticulous divers I ever met.
The Poling is only 90 feet.
I won't debate the events of Paul's death here because Paul was a friend of mine also and he did a stupid thing that no rebreather diver should have.
bleeb:I've never dove a rebreather and was wondering. A lot of (higher-end) rebreather training seems to require (prior) deco knowledge and experience, presumably because it's easier to incur deco requirements with them. How much is this an issue with so-called 'recreational' rebreathers, or how does the training for these units deal with depth/time limits? With repetitive multi-level dives, do you end up being more reliant on the dive computer than on OC? Or are these types of units heavily dependent on computers to operate them, and the added risk of depending on them for nitrogen loading is relatively small?
The training for the rec type rebreathers leans more toward knowing the unit's functionality and safe operation and less on survival modes. When recreational diving there is one appropriate response to any perceived problem 'bail out'. In technical rebreather training there is more "if this happens do this" type of responses. Deco training iss not required for recreational RB training and although you can get yourself well into deco before your gas supply runs low the diver must be observant of their limits. Multi level dives can easily be planned using desktop software or even a nitrox computer and this planning is covered in the course. I have included an OC multilevel profile and the same profile on CCR. As you can see the OC profile requires over 8 min of deco even using 30% nitrox. The CCR profile has just 1 minute of deco using air diluent. Also note the gas requirement for dive 1. It would be considered a technical dive on OC but is a recreational dive on CCR.
Speaking for the ISC Predator type RB the philosophy behind it is a very simple RB with very simple operation. The Poseidon RB that TS&M speaks about takes the opposite approach. Very complex electronics which does everything for you (as long as it works)
Consider the following 2 profiles:
Decompression model: VPM - B
DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 2
Dec to 50ft (1) Nitrox 30 50ft/min descent.
Level 50ft 9:00 (10) Nitrox 30 0.75 ppO2, 41ft ead
Dec to 100ft (11) Nitrox 30 50ft/min descent.
Level 100ft 19:00 (30) Nitrox 30 1.21 ppO2, 85ft ead
Asc to 80ft (30) Nitrox 30 -30ft/min ascent.
Level 80ft 20:00 (50) Nitrox 30 1.03 ppO2, 67ft ead
Asc to 20ft (52) Nitrox 30 -30ft/min ascent.
Stop at 10ft 8:20 (61) Nitrox 30 0.39 ppO2, 5ft ead
Surface (61) Nitrox 30 -30ft/min ascent.
OTU's this dive: 55
CNS Total: 18.8%
113.6 cu ft Nitrox 30
113.6 cu ft TOTAL
DIVE PLAN COMPLETE
Same dive on CCR
Decompression model: VPM - B
DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 2
Dec to 50ft (1) Diluent Air 1.20 SetPoint, 50ft/min descent.
Level 50ft 9:00 (10) Diluent Air 1.20 SetPoint, 23ft ead
Dec to 100ft (11) Diluent Air 1.20 SetPoint, 50ft/min descent.
Level 100ft 19:00 (30) Diluent Air 1.20 SetPoint, 86ft ead
Asc to 80ft (30) Diluent Air 1.20 SetPoint, -30ft/min ascent.
Level 80ft 20:00 (50) Diluent Air 1.20 SetPoint, 60ft ead
Asc to 10ft (53) Diluent Air 1.20 SetPoint, -30ft/min ascent.
Stop at 10ft 1:00 (54) Diluent Air 1.20 SetPoint, 0ft ead
Surface (54) Diluent Air -30ft/min ascent.
OTU's this dive: 72
CNS Total: 25.5%