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This is so good I had to copy it for you all
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We at the factory get to hear the details of all the deaths and most of
the near misses.
I can't give specific details but please take a look into the following
areas:
1) Trimix diving:
Three divers have died doing decompression dives (2 were trimix, one was
deep-air (yuk) ) when they had only been trained to the basic level and
their experience amounted to less than 6- 20 hours on rebreathers.
After the initial training course, you need to build your experience again
gradually. Do some beach dives, some RIB dives, some hard boat dives. Do
ascents up shot lines, try some ascents without shot lines, try some
ascents when launching your SMB from the bottom. Try ascents launching the
buoy from mid-water. Try ascents using the Mary Poppins technique, really
nail your buoyancy control - make sure you will be able to do those
deco-stops. A trimix dive requires better than average buoyancy control
during ascents. Keep the ascent under control from the word go.Once it
starts to get out of hand it is difficult to recover control.
Practise and practise, so when it comes to doing the more
advanced training you can absorb more easily the new stuff.
AND when you change some of your kit - like introduce a new dry suit, a
new reel, a new mask, anything - go back several steps and start again.
NEVER do a Trimix dive with any piece of new kit. Take it on a bimble dive
first.
2) Switch the oxygen on first then the handsets. You get a better battery
test.
If you get a battery warning underwater - what do you do? - Switch it off
and let the Slave take over and consider aborting the dive.
What you don't do is continue with the dive ignoring the beeps. If you get
another problem crop up - low oxygen, high oxygen, cell warning, you'll
miss it.
3) Take the buzzer seriously ! I know very few divers that can asses
properly a persistent "Cell warning" to a sufficent level of expertise to
be able to continue the dive. Don't even consider doing it - you might be
wrong - the machine is telling you there's something wrong. Abort the
dive.
4) Aladdin Nitrox dive computer:
If you take it on a trimix dive - you bend it. It then sulks for a day or
two and is unusable for a while. To stop this happening some put the unit
onto 50% O2 - so below 20m or so the thing is beeping at you continuously
as it thinks your PO2 is too high. Does it drown out the Inspirations
beep? - I don't know for sure- but I do know that two have died when using
beeping Aladdins.
5) Some divers insist on waiting for the buzzer.
If it isn't turned on and in dive mode - you are not going to get a buzzer
!
LOOK AT THE HANDSETS!
There is no substitute. You cannot go through the dive waiting for the
buzzer, you MUST know what you are breathing at all times.
When you put the mouthpiece in (Ding! What am I breathing?) - pick the
handset up and look at it.(Oh dear I forgot to turn it on - silly me.)
6) Looking at handsets shouldn't be a hit and miss process - plan it out -
Specify waypoints where you WILL devote time to the handsets - regardless
of what is going on.
The following waypoints are interspersed with handset monitoring when I've
got nothing better to do, which is probably once every two minutes whilst
on the bottom but much more often during the ascent.
These checks are also re-inforced by knowing how the unit should be
working at the different stages of the dive. e.g during the descent the
solenoid shouldn't be firing - so if it does - I look at the handset and
see what's going on. On the bottom, the unit is replacing just the oxygen
I metabolise so I'm not expecting long injections of oxygen. So, if there
is a long burst - I'm on the case and you'll find you can get to the
handsets and see what's happening before it hits the high O2 warning
level.- if the longer oxygen inject follows a diluent addition
then that's normal - so again you know it is functioning properly. On the
way up I'm expecting longer injects, every 6 seconds. I listen for the gas
coming in, not the solenoid clicking.
My waypoints are:
a) when I put the mouthpiece in
b) before I jump in
c) when I hit the water
d) during any longish surface swims
e) when I get to the buoy
f) when I get to the bottom
g) before I leave the bottom
h) at the start of the ascent
i) during the ascent and deco-stops and
j) during the surface swim
NEVER SWITCH ANYTHING OFF UNTIL YOU ARE BACK ON THE BOAT !
5) CCR are complex things - rubbish!
Rebreathers are all about PO2, CO2 and loop integrity.
CO2 issues (scrubber material, assembly, flow valves and direction) and
leak testing should be done the night before.
So- what concerns you during the dive ? - PO2 , PO2 and PO2.
6) Preparation
Do all the preparation before you get to the dive site. Sitting on the
side of the boat is no place to find that you should have fitted a new
battery or be worrying about the sofnolime.
As the preparation checks are done on land, it is no problem to use a
check list and even little Mike used one religiously (laminated and stuck
to the inside of his yellow case). Despite building them everyday for a
living - he still used the checklist to assemble and prepare.
Some divers have acronyms for their checks. Ewan selected "All Girls Love
Straight Sex", Kevin Gurr selected "F L A G S". My problem is I can never
remember what the letters stand for.
Also, the acronyms I've looked at in the past tend to mix up the
equipment preparation checks and the checks you should do just before you
jump in the water. (I might be wrong on this - c'os I can't remember what
the letters mean. )
These following checks are done assuming you have done all the preparation
checks and are the last checks I do before jumping in.
In the interests of keepig it simple, I use - A, B,C (Air, Bailout,
Computers).
With the unit on, I work my way from the left to the right. I check
diluent(Air), Bailout, inflator for BC, and Computers which includes the
oxygen supply.
Air -
I push the diluent button while I watch the contents gauge. This ensures
the inflator works, the hose is connected, allows me to check that the
diluent hasn't leaked out and because the needle on the gauge doesn't move
it ensures the tank valve is open. (75% of diving the population don't
know which way to turn a valve to open it and close it! - they just wiggle
and twist it until it works- then when you invert the tap and put it
behind your back it makes it even more difficult and then when one valve
points left and one valve points right which means you require a different
action for your right hand compared to your left - you can see why some
divers get it wrong. I count myself in the 25% that knows how to open a
valve and I'll risk my life on it but I still do the gauge check anyway).
Bailout-
Where is it? Bring the Auto Air forward and clip it in place, check the
BC inflation, purge and breathing functions.
Computers-
Blow into the loop one big breath while you look at the computer displays.
The numbers should crash downwards rapidly. If you blow hard enough,
you'll get the low O2 alarm to kick in as well but this for me is only an
incidental test as I heard the buzzer when I switched on the set. Then
just wait and watch the PO2 climb back up to setpoint. I'm looking for the
rate of change of the cell readings and see that it gets to setpoint. Now,
I know the cells are reacting to changes in PO2 and I know there is some
oxygen on. Then I move the oxygen inflator and push that while I watch the
O2 gauge, so again I know the tank valve is open and that I still have
enough O2 for the dive and I know the inflator works.
7) We have limits imposed on us when we dive with rebreathers.
Decompression and ascent speed limits we are all used to from our open
circuit days.
But divers really should take more notice of the
CO2 duration limit and CNS Limits.
The CNS limit is a physiological limit.
Some run at 1.4 bar but why? The deco advantage over 1.3 is minimal and
you get half an hour knocked off your CNS allowed time.
Then some of these guys additionally run pure O2 from 6m upwards - taking
the CNS way over the NOAA limits. Some cure that with airbreaks - but why
go there in the first place, if you can avoid it? Run at 1.3 or lower for
the dive and look to using a 1.4 as a max. for deco.
There has been enough written on CO2 durations. Using the scrubber for
longer than specified - kills.
Some of the above stuff and more is shown in the latest version of the
manual. If you haven't downloaded it already it is available in English
and Dutch, and soon in German on
www.drogon.net/Inspiration/Manual
Dive safely.
If in doubt about the dive - cancel it.
Martin Parker
Managing Director Ambient Pressure Diving Manufacturers of the Inspiration Closed Circuit Rebreather Water-ma-Trout Industrial Estate, Helston, Cornwall, TR13 OLW, UK. Tel: 01326 563834, Fax: 01326 573605. Website: www.ambientpressurediving.com |
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