Diver UK – August 2019

59 divEr

to train divers. At that time, agencies
were selling rebreather instructor
certifications, but the instructor didn’t
have to own a unit or have that much
experience.
It was also recognised that the sport-
diving community did not have
a supporting infrastructure like the
military’s, nor any retail support at that
time. In other words, the community
would be starting from scratch.
With regards to decompression, the
only validated constant partial pressure of
oxygen (PO 2 ) tables at the time were the
US Navy 0.7atm constant PO 2 for nitrox
and heliox rebreather diving.
Note that a closed-circuit rebreather is
designed to maintain a constant PO 2 ,
called a “set point,” throughout the dive.
It was unknown at the time whether
simply reprogramming a dive-computer
to calculate decompression based on the
oxygen levels supplied by a rebreather
would work effectively.
The forum asserted that third-party
pre-market rebreather testing was critical
to ensure reliable and high-quality
products. It also concluded that the use
of full-face masks and/or mouthpiece
retaining straps, which were standard in
military diving, and adherence to the
buddy system could improve safety.
In addition, the forum noted that the
development of on-board CO 2 monitors,
which didn’t exist at the time, could

greatly improve diver safety, and the

community was advised to adopt

a maximum constant PO 2 of 1.3atm,

similar to the US Navy.

T

HE TECH COMMUNITYwas still

arguing how high divers should run

their PO 2 for the working portion of the

dive on open-circuit trimix dives. Dr Bill

and others argued that a diver’s PO 2

should be kept at 1.4atm during the

working phase of the dive and boosted to

1.6atm for decompression, which

eventually became the standard.

Safety was viewed as the biggest

challenge in adopting rebreathers for

sport diving. As Billy Deans noted at

Rebreather Forum 2.0: “The challenge is

going to be bringing the technology to

market without killing too many divers in

the process!” It would be another decade

or so before rebreathers became a

common tool among technical divers.

Unfortunately Deans was correct about

the challenge. There were 200 reported

rebreather fatalities worldwide between

1998 and 2012, when Rebreather Forum 3

was held; there were about 10 fatalities a

year from 1998-2005, and an average of

about 20 a year from 2006-2012.

To put this in perspective, on average

there are about 100-120 scuba-diving

fatalities annually in the USA, Canada,

UK and the rest of Europe combined,

which represents the majority of the

worldwide market.

Later in 2012, Dr Andrew Fock, head

of hyperbaric medicine at the Albert

Hospital in Melbourne, Australia,

estimated that rebreather diving was

likely 5-10 times as risky as open-circuit

scuba-diving, accounting for about 4-5

deaths per 100,000 dives, compared to

about 0.4-0.5 deaths per 100,000 dives for

open-circuit scuba.

This makes rebreather diving more

risky than sky-diving at .99 deaths per

100,000 dives, but far less risky than base-

jumping at 43 deaths per 100,000 jumps.

Since 2012, the evidence suggests that

rebreather diving safety has continued

to improve.

You’ve come

a long way, baby

D

ESPITE THE EARLYcontroversy and

initial high incident-rates, technical

diving eventually found its stride and,

through improved training, the

development of standards, and

experience, was able to significantly

improve its safety record.

In doing so, it greatly expanded our

underwater envelope and knowledge, as

Dr Bill suggested in his insightful article

Call It High Tech Diving, which ran in that

first issue of aquaCorpsin January 1990:

“With all these warnings issued, and

all the described parameters met,

advanced high tech diving offers the

prepared knowledgeable diver a chance

to experience a realm not previously

accessible to humans,” he wrote.

“And there is every reason to think –

as our technology and knowledge advance –

that we will be able to push the envelope

even farther.” And we did.

TECHNICAL DIVER

Top, from left: Polly Tapson;

Designer-engineer Peter

Readey with a prototype

Prism; Tracy Robinette

(standing) with Dr Max Hahn

at Rebreather Forum 1.

Left: Diver on the bow of the

120m-deep Britannicduring

the 1998 expedition.

Below: Rob Palmer of TDI

teaches a Dräger Atlantis

semi-closed-circuit instructor

course.

PETER READEY

ALL IMAGES OTHER THAN

THOSE ATTRIBUTED FROM

THE AQUACORPS ARCHIVES

ROB ROYALE

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