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I am reposting this because it did not seem to have gone through the list
serve......the attached file on O2 Sensors it refers to, was just posted by
me last night, and was taken from (with permission)
Kevin Gurr in the new IANTD Rebreather Diver Student Manual & Workbook,
If you have gotten this already, my apologies.
Dan
===========_12526364==_"
Date: Wed, 27 Mar 1996 22:45:51 -0500
To: techdiver@terra.net
From: diveusa@ga*.ne* (diveusa)
Subject: rebreather irresponsibility
Cc: dlv@ga*.ne*
To: Dan Volker, S. Florida Dive Journal. From: Jack Kellon
Re: the internet piece you forwarded to me from Rod Farb, I'll have to say
that the vitriolic reactions we get from some people never fail to surprise
me. Usually they are from people that plug the use of galvanic oxygen
sensors, the most inherently unreliable piece of electrical equipment I
have had to work with in a marine environment. Many of them have shown a
need to put their brain in gear before engaging their mouth. NOT ONE OF
THESE CLOWNS HAS EVER BOTHERED TO ASK HOW THE SYSTEM WORKS. They all seem
to think that everyone in the industry should immediately respond to their
half-baked views based on limited experience, and that all equipment should
correspond to their view of what a rebreather should be, whether they know
what they're talking about or not.
I think I know who Farb has been talking to, and they tell me they have
been misquoted and/or taken out of context.
Just a few points:
1. The Odyssey designs were made by someone with over thirty years of
rebreather experience in both equipment design and use, with help from
others. I have seen many criticisms of the unit on the tech diver list by
people that do not even know how the operating system works. For the
record, the unit was designed to fill a niche between semi-closed mass
flow systems (which I consider to pose too high a risk of hypoxia) and
electronic closed circuit systems that are very complicated and rely on a
genre of historically unreliable sensors. There are other issues as well,
including the failure of electronic indicating alarms during task overloads
and the amount that system complexity contributes to the overload.
2. The first unit was built in July 1995. The company was incorporated in
September 1995. Eight subsequent units were built using three different
versions of the basic operating system, all of which were chamber tested
for the linearity of the discharge proportioning system during rapid depth
increases and decreases. Five shells of the latest version were built by a
company in Ft. Lauderdale, of which only one has been delivered as a
completed unit. By the way, Biomarine has taken more time just to repair
two units that I know of than we took for the development process to date.
But it really doesn't matter. If you are productive, some idiot will accuse
you of unsafely rushing the process, if you're not, the same idiot will
accuse you of developing "vaporware".
3. The units are built to order. We are talking to more than one
manufacturer to see about getting a new model (smaller and lighter) into
production.
4. Yes, we're small. Had I realized that it's a crime in some people's
minds to start a company to develop new technology that improves diver
safety and work up to the point where you have to approach a larger company
to put the advance into production, I never would have done it. I'm far too
concerned about the opinions of loudmouthed half-wits to actually put
effort into doing something. Far better to sit back, forget all my
experience and training, and become one of the legion of self-appointed
"experts" who feel it's their duty to be critics. Ah, the safety and
camaraderie of being one of the thundering herd of ego-driven
techno-nitwits.
5. A little less than a quarter million has been thrown into this project
to date. Although my personal financial liabilities are high, company
liabilities are less than $10,000.
6. There was some conversation on the tech diver list lately that
absolutely astounded me. A Peter Den Haan was corrected for saying that
electronic closed circuit units were ten times as complex as semi-closed
units. If anything, ten times may be conservative, based both on the number
of components and the individual operations they must perform. Like Den
Haan, I have also spent over thirty years designing and servicing
electromechanical devices IN MARINE ENVIRONMENTS. Anyone who doesn't
believe in the added problems posed by electronic components and batteries
is kidding himself and should confine his comments to subjects that he has
more knowledge of. Although it's a gross comparison, use of a rebreather
doesn't impart technical knowledge of its inner workings any more than
bringing in the newspaper teaches the family dog how to read. The argument
I saw for downplaying the complexity of rebreather electronics was similar
to saying that a stereo receiver/amplifier and its two speakers each
comprise one third of the complexity of the system because each is housed
in its own case. People that don't do engineering shouldn't be arguing with
those that do over engineering considerations any more than engineers
should be arguing with ichthyologists over their field of expertise, at
least not on the basis of having been lifetime fishing enthusiasts.
7. While everyone is trying to enhance their image as a rebreather guru,
they are missing three of the most important safety considerations.
a. The rebreather being used for any dive should be as simple as
possible while still meeting operational and safety requirements. This
means not using a rebreather at all if its only purpose is to identify the
user as a "superdiver".
b. If you want to be a rebreather authority, you should first
become ` thoroughly familiar with the technical differences between the
various operating systems and dive each type to become familiar with its
strong points and weak points. Believe me, they all have both.
Please don't, through omission or unqualified viewpoints, pass your lack
of knowledge on to others.
c. Do something constructive. Stop the proliferation of courses
that take an instructor with no prior rebreather experience or
knowledge (except the unqualified garbage he reads on the tech diver list)
and turn him into a rebreather instructor in three days. I wonder how
many of the more vocal characters on the tech diver list are engaged in
this highly irresponsible activity for profit?
8. A little homework on rebreather history wouldn't hurt the loudmouths
either. Apparently these little boys haven't been around long enough to
remember the deaths on electronic units that caused the Electrolung to be
pulled from the market. Also, I haven't seen much about the two Biomarine
hypoxia-leading-to-unconsciousness incidents that had commercial diving
industry bigwigs diving into the pool to rescue the company
instructors/demonstrators on two different occasions. One of the units
involved even had a heads-up display. How about it Farb, care to explain
why this happens?
9. Some of the loudmouths are presumably good rebreather divers and feel
quite comfortable with their units. These must be the same people that
assume that because their home has never been destroyed by fire, they don't
need fire extinguishers. Hopefully, the incident that could very well cost
them their lives won't. If it doesn't, it will surely change their
attitudes.
10. I've seen a number of notes on the tech diver list about how easy it is
to build a rebreather. For pure oxygen units, this is probably true if the
builder is aware of some basic problems relating to hydrostatic lung
loading and dynamic breathing resistance. Anyone who thinks he can do this
with any other kind of unit probably doesn't know how much he doesn't know,
and may well become a statistic.
11. Some idiot suggested that an oxygen sensor be attached to pure oxygen
rebreathers because of a recent Canadian death. Then a couple of wannabes
jumped on the bandwagon in agreement The thing that would have prevented
this death is training on counterlung purging procedures and the reason for
them. Training, not the addition of a component more likely to fail than
the unit itself, is the answer here.
12. I'm attaching a very well written section on galvanic oxygen sensors by
Kevin Gurr in the new IANTD Rebreather Diver Student Manual & Workbook,
Module 1. I consider this to be the most rationally written description of
galvanic oxygen sensors I've seen to date. Please keep in mind that it was
written by a man who is actively involved in the design of electronic
closed-circuit rebreathers.
Disgusted with the irresponsible behavior of the emerging self-styled
rebreather "gurus" strutting their ignorance on the tech diver list,
Jack
Attachment Converted: C:\E-MAIL\sensors2
xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Dave Schubert
Instructor Trainer: PADI, IANTD, DAN
Rebreathers...Nitrox... Photo...Video
1201 N. Ocean Drive
Singer Island, FL. 33404
407/844-5100, FAX: 407/848-0627
Webpage: http://www.florida.net/scuba/diveusa
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Dan Volker
SOUTH FLORIDA DIVE JOURNAL
"The Internet magazine for Underwater Photography and mpeg Video"
http://www.florida.net/scuba/dive
407-683-3592
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