Karlīs Rebreather Page
Rebreather, Oxygen, Nitrox, Trimix & Heliox FAQ
Welcome to the Rebreather, Oxygen, Nitrox, Trimix & Heliox FAQ.
Just write me, if You have a question or a bulletin and want to see it here.
- This page only contains threads that are too small for an own page in the Rebreather Index
- > I have heard that
has a lower narcotic level than compressed air,
> is this good for deep dives ?
No Bonzo, no, Nitrox is only good for semi-shallow dives to 40m or less.
Under higher partial pressure Oxygen becomes toxic. To find out more read the O2-Tox-Page.
- > I saw a diver using a DIN (R5/8") Connection for Nitrox,
> can I do this too and use my normal Regulator for Nitrox or pure Oxygen ?
No Bonzo, no, don't be so mad to use your normal Air Valves or Air Regulators for anything else than Air. To find out more read the Gas-Code Page.
- > I want to buy a Rebreather but I heared it would be impossibel
> to do good buoyancy fine control without hands.
> So how can I use a Rebreather when doing UW-filming work ?
Don't worry, your first step before buying a Rebreather is getting qualified to dive one.
So ask the training facilities on which type of Rebreather they can teach you to do good buoyancy fine control without hands.
I found out how to do a real good buoyancy fine control without using my hands when
diving with LAR5, Atlantis-1/Dolphin, FGT-1 and IDA-71
and I engineered a gadget that allows fully hand-free buoyancy fine control on CCR-rebreathers like the Buddy-Inspiration.
- > Hi, can I adjust my Oxygen-Sensors at the surface with pure Oxygen (1bar ppO2)
> and then dive with a Solenoid Setpoint of 1.6bar ppO2 ?
Be careful, if it works fine with new Sensors that's no Garantee that it will still work after they degraded to old ones.
As sensors age, the output voltage will plateau at some point, so you will get too low readings on values above the calibration point.
Worst case all 3 sensors have the same age, display exactly the same wrong result (this is pretty unlikely)
and let the ppO2 raise to a much higher value than you intended.
1.6bar is quite high Oxygen-partial pressure if constant for the entire dive, it will limit the time of your dive.
I would suggest to dive a ppO2-setpoint of 1.0bar
(Caution: think about EAD, I prefer long shallow dives) and
check on pure Oxygen in shallow water (or in the pressure-pot) if the reading is still linear above your setpoint,
e.g. you should read ~1.6bar ppO2 in 6m.
- > I am riding a Buddy Inspiration, can I fill the Diluent Bottle with pure Helium for deep dives ?
No Bonzo, no !
#1 You shall only do what you are certified for.
#2 Your Diluent is your Bailout too, it has to be breathable, that means at least 16% O2.
#3 Think about Dekompression and only do the dives your bailout logistic allows.
- > Is Heliox-Rebreather Diving an expensive black magic ?
No, don't worry. Ok, you need to get qualified for it, but it is not much more expensive than running your CCR as Nitrox-Rebreather.
Even in Germany you can afford to dive Heliox if you ride a CCR,
a fill of a 50 liter 200 bar storage tank with Heliox16 costs about 200Euro here and should last for more than 20 dives.
Diving with Heliox is not a black magic at all, it's a responsible way to handle the problem of nitrogen-narcosis,
but you need to know how to handle Helium Decompression-Tables and be wise enouth not to reach out for HPNS.
- > I've noticed no thermal difference between trimix and heliox,
> I imagine because of the heat generated in the rebreather-loop.
Hi, you discovered the termal capacity bug that is still found in some books 
Helium has a significant higher termal capacity per mass, but you breath per Liter,
at given pressure that means per Mol (1mol=22,4bar*liter), and so it has a lower termal capacity.
Cp (He)=20,9 Joule/(mol*Kelvin)
Cp (N2)=29,0 Joule/(mol*Kelvin)
Cp (O2)=29,3 Joule/(mol*Kelvin)
In units that fit for Divers:
Cp (He)=0,933 Watt*sec/(bar*Liter*Kelvin)
Cp (N2)=1,295 Watt*sec/(bar*Liter*Kelvin)
Cp (O2)=1,308 Watt*sec/(bar*Liter*Kelvin)
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