Diving magazines are full of ads
and hoopla about rebreathers, trying
to get the sport diving community to
make them their next big purchase.
However, rebreathers are extremely
expensive (like five figures!), and a
spate of recent deaths has given
them the image of being complex
and dangerous.
Many U.S. divers know little
about rebreathers beyond their
basic function: the ability of some
units to purge carbon dioxide from
recycled air and to eliminate
exhaled bubbles, making them a
boon to photographers and those
who want to approach big fish.
Rebreathers are not new.
Because of their quiet operation,
stealthy lack of bubbles, and the
long dive times they enable,
rebreathers have been used by the
military for years, including
extensive use in WWII. Civilian use
includes underwater photography,
above-ground mine rescue, and
underwater scientific expeditions
such as cave exploration. Their
encroachment into the recreational
market has been recent, although
several live-aboards and a few
resorts now rent them after giving
divers a short training course. In
places like Cocos Island, their lack
of bubbles helps divers approach
the big pelagics.
Rebreathers have made few
inroads into the U.S. sports diving
market. While they were on center
stage at the Diving Equipment and
Marketing Association shows in
1997 and 1998, at the 1999 New
Orleans show their promotion had
been greatly reduced.
In the U.K., safety concerns are
so severe that last fall the British
Sub-Aqua Club (www.bsac.com)
announced it was prohibiting its
50,000 members from using
rebreathers on BSAC dives. Although
the BSAC subsequently
modified its stand to enable the use
of semi-closed circuit rebreathers,
the use of closed-circuit rebreathers
within the BSAC is still prohibited.
According to DAN’s Joel
Dovenbarger, DAN is aware of only
two rebreather deaths in the U.S.,
one in Washington state last year
and the highly-publicized death of
72-year-old Nobel-prize-winning
physicist Henry W. Kendell during the Wakulla 2 cave exploration this
past February. The circumstances
of Kendell’s death certainly sparked
rebreather controversy. Kendell was
diving alone, in clear violation of
both Wakulla’s rules and Florida
state parks regulations. After his
body was recovered, the team
doctor issued a report that a valve
on Kendell’s Cis-Lunar MK-5
rebreather was improperly adjusted,
which caused him to black
out due to lack of oxygen. Later,
the Florida State Medical Examiner
determined that Kendell had
suffered a fatal gastrointestinal
hemorrhage. Subsequently, the
Wakulla 2 Expedition issued a statement that Kendell “died from
natural causes and his unfortunate
death bore no relationship to either
the pre-dive procedures that he
followed that day or the dive equipment
that he used. [We regret] to
have rushed to judgment.”
. . . rebreathers are
extremely expensive
and a spate of recent
deaths has given them
the image of being
dangerous as well. |
However, the rash of 1998
British rebreather deaths are cause
for concern. Besides the Cis-Lunar
MK-5 death at Wakulla, according
to industry sources there have been
four rebreather deaths attributed to
the Buddy Inspiration, six associated
with Draeger (www.draegerdive.com)
units, and one linked to a Carleton
Mk16 rebreather. Not all final
autopsy reports have been completed,
and the BSAC says that it’s
not prepared “to comment speculatively
on the cause of any of the
individual rebreather fatalities.” But
one conclusion is obvious: according
to Martin Parker, owner and
managing director of AP Valves,
which manufactures the Buddy
Inspiration rebreather, as of Feb.
23, 1999, the statistics stood at 4
Buddy Inspiration deaths out of
4000 Inspiration rebreather hours
dived. Whatever the cause, statistically
this is an incredibly high rate.
Manufacturers such as Carleton
(www.carltech-marine.com) and
Inspiration defend their products but
are not permitted to comment on the
deaths until after the autopsy reports
have been filed. However, industry
spokesmen did tell Undercurrent that
the Royal Navy had informally
reported that some of the deaths are
due to natural causes, and these
spokesmen also said that preliminary
reports in other incidents pointed to
“the user making fundamental
mistakes with regard to basic equipment
assembly, setup, or monitoring.”
Still, if deadly errors are this easy to
make, shouldn’t users have cause for
concern?
Rebreather models vary
considerably. There are variations
between computer or mechanically
controlled units and single mix or multiple gas units as well as basic
design differences between closed
and open-circuit rebreathers.
(Closed circuit units totally recirculate
the breathing gases, keeping
the proportions of the gases in
balance by employing a sensor to
add oxygen when it falls below the
specified level and using a scrubbing
material to absorb and remove
excess carbon dioxide. They eliminate
exhaled bubbles except on
ascent, when they release the
expanding gases to stabilize pressure
on the breathing loop. Semi-closed or
open-circuit units, on the other hand,
use a compressed-gas supply and a
regulator, and the units discharge
exhaust gases, including some
oxygen, with each breath.)
Units have a wide scope of
possible mechanical problems
ranging from flooding the breathing
loop to maladjustments in the
sensors that control the gas mix.
Maintenance is involved and pricey,
especially with models that incorporate
oxygen sensors. The training
required to use rebreathers safely is
far more extensive than, say,
training for Nitrox certification.
Because of the wide variation
between models, there are substantial
differences in training programs.
Charges of inadequate
training and cavalier attitudes
toward rebreather usage have been
bandied about extensively in
explanation of the recent deaths.
Rebreathers have also been
associated with a wide range of
possible medical problems, any one
of which can precipitate a serious
dive emergency. Sudden depth
changes can stymie rebreather
electronics: a quick ascent, especially
one where a diver is working
against a strong current, can result
in oxygen dropping below safe
levels. An abrupt descent can cause
the opposite problem. There are
added risks of hyperventilation and
carbon dioxide buildup as well as
unique decompression sickness
considerations for closed-circuit
and open-circuit systems. Oxygen
toxicity is possible at any depth and
can be acute at shallow depths.
While official confirmations of
cause of death have not been
released in many incidents, some
unconfirmed reports have pointed
toward natural causes, operator
error, and inadequate backup
systems. The fact that accidents
seem to occur at different stages of
the dive, some on the bottom, some
on ascent, and some on descent,
makes it hard to spot a trend,
although in some instances the
suspected cause of death has been
oxygen poisoning. Unconfirmed
reports regarding problems with
units recovered after fatal or nearfatal
accidents have also been
varied, with reports mentioning
recovered units in which the
oxygen was turned off, units which
did not have an open-circuit bailout
fitted, and units which weren’t in
“dive mode” when the diver
entered the water, a situation that
reportedly would make it impossible
for the user to control the
oxygen level.
Many deaths have reportedly
involved divers with extensive opencircuit
scuba experience but only
minimal rebreather training and
experience. AP Valves, manufacturer
of the Buddy Inspiration
(www.apvalves.com), has reportedly
begun offering additional free
training to all owners. Unfortunately,
the question of how much
training is enough has yet to be
definitively addressed by the
industry. Manufacturers require
training when units are purchased,
but there are no industry-wide
training requirements and little
agreement about either how much
training is necessary or what constitutes
safe rebreather design. Issues of
how much redundancy to build into
units, what sensors and displays
should be included, and whether
control systems should be computerized
or manual have been left up to
manufacturers and purchasers.
Cost is certainly a factor. For
example, it’s hard to fault the triple
redundancy built into the Cis-
Lunar MK-5P, and the company’s
training requirements are extensive
(to purchase the unit, they require
a 7-day basic training course that
qualifies divers to use their MK-5P
to a maximum depth of 165'), but
the $17,500 price tag, which does
not include the cost of training, is
hard to swallow. (For more info on
Cis-Lunar, see www.cis-lunar.com.)
While some may view the BSAC
response to the U.K. deaths as
alarmist, it’s certainly a fledgling
effort to set initial industry-wide
standards, albeit conservative ones.
The BSAC’s current position on rebreather use permits only semiclosed
circuit rebreathers using Nitrox
(no pure oxygen rebreathers are
permitted); users must carry an opencircuit
bailout, and dives cannot
exceed 40 meters. The BSAC’s recommendations
for rebreather users on
non-BSAC dives are less stringent and
appear aimed at the identified problems:
get comprehensive training;
follow manufacturer’s recommendations
for preparation, maintenance,
servicing, and operation; gain progressive
shallow-water experience before
attempting deeper dives; stay above 50
meters; use only air, oxygen, or Nitrox;
and don’t dive alone.
Experienced divers have spent
years buying new pieces of equipment
and sticking them on their backs, but
using rebreathers takes more than a
little getting used to. Because buoyancy
and exhalation are so different from
open-circuit scuba, there’s enough of
an “unlearning curve” that some
instructors actually claim that novice
divers may have an advantage in
mastering rebreather use. Given the
units’ complexity, the deaths of several
experienced divers, and such extensive
differences between rebreather models
that you can’t switch from one to
another without additional training,
there’s plenty of reason for caution. In
fact, that’s a concession that even
manufacturers are making. Martin Parker
offers this succinct advice: “The diver
needs to change his open-circuit thinking
and remember one thing — you do not
breathe from the loop unless you know
what you are breathing.”
Diver Barry Lee Brisco offered this
summary of the problem from last
September’s “Rebreather Forum 2.0”
organized by Michael Menduno in
Redondo Beach, California:
“At the top of the agenda was the
fact that although extensive training is
mandatory when a rebreather is
purchased, there are no industry-wide
training standards in place, [a situation]
reminiscent of the fledgling dive
industry forty years ago.... Training
standards are complicated by the fact
that rebreathers vary significantly in
design. This is in contrast to opencircuit
scuba, where from the diver’s
point of view, one regulator is used like
another: air on, purge, and go. Try that
with a rebreather you haven’t been
trained on and you are more than
likely to end up a fatality statistic.”
— John Q. Trigger