Rebreathers

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VK - 10 Jul 2007 07:48 GMT

I never thought it would happen, but I am considering purchasing a
rebreather for underwater photography and I wanted to get some
feedback from the folks here about whether or not that is a good
choice for me.

Intended use: photography (bubbles scare away a lot of subject). I
will use air/nitrox and stay within NDLs. This is not for tech use
and I have no plan of ever using mix here (I'll stick to open circuit
for that, thanks very much).

I consider myself a fairly responsible diver at this stage of my life
- reasonably conservative profiles, always watch air/depth/time,
etc.

My big concern with rebreathers has to do with how much care &
maintenance they need. Last I looked into rebreathers (7 years ago),
they required as much fussing over as an Argentinian girlfriend.

To put it in perspective - I service my regs once every 5-6 years, my
wings both autoinflate and leak and have been doing so for a year. I
am not really that fussed over gear. However, I am capable of making
the effort where it matters (my tech rig is immaculate, and I do all
the requisite fussing over my u/w housing).

I guess what I'm getting at is - how much care and maintenance do
rebreathers really need? If it is something where you have to be
VERY anal-retentive or risk death, I am not going to bother. If it is
something where you to go through a certain checklist before and after
for general safety, I can manage that.

Also, any recommendations on a good, low-fuss rebreather?

V.

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ben bradlee - 10 Jul 2007 10:18 GMT

> I guess what I'm getting at is - how much care and maintenance do
> rebreathers really need?

The last I checked it was way too much. You need to keep the inside clean.
I understood it to be cleaning the unit after each use. Moisture builds up
inside the closed circuit. You can get mold and general rot that will grow
in warm (or cold, or in-between) air inside the closed circuit. Don't clean
it and its sure to make you sick. There are more down sides besides the
cleaning but that's the biggie for me.

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Matthias Voss - 10 Jul 2007 11:07 GMT

> I guess what I'm getting at is - how much care and maintenance do
> rebreathers really need?

I a nutshell:
It begins with controlling the nitrox mix. One death is
attibuted to a leak in a membrane system.
Always know your mix...
I write this because the obvious choice for you would be a
semiclosed rebreather. These offer the least complex set of
matters.

If it is something where you have to be

> VERY anal-retentive or risk death, I am not going to bother. If it is
> something where you to go through a certain checklist before and after
> for general safety, I can manage that.

Checklists, and function checks. And dive planning.
With a constant mass flow rig, having the right flow is
essential, that mean, keep the orifices clean (no ways a new
concept, really), and stick to your dive plan. Avoid low
depth exertion. Have sufficient OC bailout to end each dive
from bottom time.

With a passive SCR, like the RB 80 (expensive..) operation
is safer, but a different set of depth limitation has to be
observed, because of the tricky math.

This puts choices down to:
Draeger Dolphin
Draeger Ray ( discontinued)
Submatix
as SCRs,
Halcyon RB 80 or a clone, for PASCRs.( takes some
involvement to get the training, to say the least)

Stay away from crappy Italian stuff.
You'd like to have some ( a different) control of your
balance, when diving a Draeger. There are kits to mount it
to a backplate (www.tec-me). Recommended.
Or you can mount it to a Poseidon Luigi jacket. Excellent.

When you get accustomed to it, you may want to add
subphysiological oxygen flow, which makes it almost
equivalant to an electronic controlled rebreather,
comfortwise. It is a different league. You have to have
redundant oxygen control, and really use it. Not every
photographers cup of tea.

Otherwise, did you consider using a modern two hose, like
the new Aqualung? Puts the bubbles away, somehow, and is not
as noisy normal OC.

Matthias

> Also, any recommendations on a good, low-fuss rebreather?
>
> V.

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Scott - 10 Jul 2007 14:04 GMT

> > I guess what I'm getting at is - how much care and maintenance do
> > rebreathers really need?
[quoted text clipped - 50 lines]
>
> > Also, any recommendations on a good, low-fuss rebreather?

Most important gear for safe RB diving is training.

Also, don't forget the Megalodon w/COPIS http://www.customrebreathers.com/

And the KISS http://www.jetsam.ca/kissclassic/Kissclassic.html

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Greg Mossman - 10 Jul 2007 15:07 GMT

> It begins with controlling the nitrox mix. One death is
> attibuted to a leak in a membrane system.
> Always know your mix...
> I write this because the obvious choice for you would be a
> semiclosed rebreather. These offer the least complex set of
> matters.

> Checklists, and function checks. And dive planning.
> With a constant mass flow rig, having the right flow is
> essential, that mean, keep the orifices clean (no ways a new
> concept, really), and stick to your dive plan. Avoid low
> depth exertion. Have sufficient OC bailout to end each dive
> from bottom time.

With an Oxy2-type transmitter integrated into a Drager, the mix will
be measured on the fly. Likewise, the computer (and redundant ppO2
monitor) will alert the careless photographer to hyperoxic conditions
by beeping frantically. So even with unknown mix and clogged
orifices, the Drager shouldn't kill its user.

Ben mentioned the PITA of cleaning the thing. That isn't too bad
since there aren't too many parts to clean. Likewise, the small
checklist to run through isn't much worse than what open circuit
divers should do. What I hated was dealing with the absorbent since
it's dusty caustic stuff. I also feared getting a caustic cocktail or
even hypercapnia from something screwing up. But with ExtendAir-type
canisters, all that work is done (at an extra price, of course).

Heck, Vandit might even be able to score a fully-loaded barely-used
Drager from a fellow rec.scuba who has one sitting in storage, you
never know.

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VK - 10 Jul 2007 15:26 GMT

Thanks for the suggestion, guys.

An SCR is what I was thinking of, although thanks for the tip on
Aqualung, Matthias - I'll check it out - our dive shop uses all
Aqualung gear, so I may be able to get a good deal on that from the
distributor :)

> Heck, Vandit might even be able to score a fully-loaded barely-used
> Drager from a fellow rec.scuba who has one sitting in storage, you
> never know.

Do tell!

Vandit

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Matthias Voss - 10 Jul 2007 16:35 GMT

> Thanks for the suggestion, guys.
>
> An SCR is what I was thinking of, although thanks for the tip on
> Aqualung, Matthias - I'll check it out - our dive shop uses all
> Aqualung gear, so I may be able to get a good deal on that from the
> distributor :)

Aqaulung is the distributor for Draeger anyway.

Matthias

>>Heck, Vandit might even be able to score a fully-loaded barely-used
>>Drager from a fellow rec.scuba who has one sitting in storage, you
[quoted text clipped - 3 lines]
>
> Vandit

Reply to this Message

Matthias Voss - 10 Jul 2007 16:34 GMT

>>It begins with controlling the nitrox mix. One death is
>>attibuted to a leak in a membrane system.
[quoted text clipped - 15 lines]
> by beeping frantically. So even with unknown mix and clogged
> orifices, the Drager shouldn't kill its user.

Yes, but the OXY 2 is discontinued, and Uwatec does not
change batteries on older Air X Oxy computers. The newer
ones do not monitor ppO2 any more.

> Ben mentioned the PITA of cleaning the thing. That isn't too bad
> since there aren't too many parts to clean. Likewise, the small
[quoted text clipped - 3 lines]
> even hypercapnia from something screwing up. But with ExtendAir-type
> canisters, all that work is done (at an extra price, of course).

There will be probably more of such available. The Extendair
does not scrub to well. As for the hassle, never had a
cocktail. I always use a vac to get out the dust particles
before diving.

> Heck, Vandit might even be able to score a fully-loaded barely-used
> Drager from a fellow rec.scuba who has one sitting in storage, you
> never know.

I bet so ;-)

Matthias

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Scott - 10 Jul 2007 16:53 GMT

> There will be probably more of such available. The Extendair
> does not scrub to well.

I know of several people who have used and abandoned the cartridges after
getting headaches.

> As for the hassle, never had a cocktail.
> I always use a vac to get out the dust particles
> before diving.

Or fill in front of a gentle fan.

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Greg Mossman - 10 Jul 2007 22:13 GMT

> Yes, but the OXY 2 is discontinued, and Uwatec does not
> change batteries on older Air X Oxy computers. The newer
> ones do not monitor ppO2 any more.

All the better reason to get the barely-used rec.scuban version.
Actually, the Air Z O2 is a bit used, a couple hundred or so dives on
(but newly changed batteries). The Oxy2 only has two dives on it,
however. Obviously it needs new O2 sensors, but those should still be
available somewhere.

> There will be probably more of such available. The Extendair
> does not scrub to well. As for the hassle, never had a
> cocktail. I always use a vac to get out the dust particles
> before diving.

Like I said, hassle. I never vacuum my open-circuit rig. Give me
open circuit or give me death!

> > Heck, Vandit might even be able to score a fully-loaded barely-used
> > Drager from a fellow rec.scuba who has one sitting in storage, you
> > never know.
>
> I bet so ;-)

No fish pictures are worth the rebreather hassles, in my opinion. Or
it's a lot easier to improve one's breath-holding skills.

Reasonable offers considered.

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VK - 11 Jul 2007 06:31 GMT

> No fish pictures are worth the rebreather hassles, in my opinion. Or
> it's a lot easier to improve one's breath-holding skills.
>
> Reasonable offers considered.

Hmm. I'm not buying it just yet - need to do a bit more digging right
now - but I'll drop you an email when I'm about to purchase.

Reply to this Message

Greg Mossman - 11 Jul 2007 21:34 GMT

> > No fish pictures are worth the rebreather hassles, in my opinion. Or
> > it's a lot easier to improve one's breath-holding skills.
[quoted text clipped - 3 lines]
> Hmm. I'm not buying it just yet - need to do a bit more digging right
> now - but I'll drop you an email when I'm about to purchase.

It's not going anywhere, unless the water seriously warms up around
here.

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