Inspiration AdvocacyA rebuttal of George Irvine's "Buddy Inspiration or Expiration?" article.
GI3's rather infamous, and now somewhat dated, article on the Inspiration comes up in the group every so often and gets knocked back again. The following was collated by Dominic Humphries from various comments posted to one of threads spawned by the article.
Georges's comments are labelled in blue, the group's responses in black. While the rebuttal information was collated from various sources, alot of it originated with Vic Watson.
|Comments from the thread...|
There is a small metal screw inside the oxygen
sensor compartment, it is located directly across from sensor number two.
Condensation often forms on this metal screw and will allow droplets to fall
onto the oxygen sensors. This will happen particularly if the diver moves
from side to side as in dumping gas from a drysuit or if they invert from
horizontal for any reason.
This is the fixing point for the battery
box. Condensation can form on this screw under high-humidity conditions
(such as the end of a dive). But droplets only go anywhere near the sensors
if you tip a damp unit on its back. This is why users are very cautious
about how the unit is handled post-dive; it can sit upright, or it can be
laid on its front without hazard.
Condensation is inherently found within this
area and will form on the oxygen sensors even without this metal catalyst.
This just doesn't happen with the proper
cells in place. Using cheap replacements may pose some risk, so don't use
cheap replacements. The recommended cells have a hydrophobic membrane on the
face and a conformal coat on the board. They are not affected by moisture.
The O2 sensors are located on the inhalation
side of the breathing loop, so you have warm gas that just went through the
scrubbing process meeting with cooler gas that you will inhale thus the
condensation forming on the cell faces. This condensation causes
discrepancies/inaccuracies within the cell readings and they begin to VOTE
trying to figure out which one is more than .2 bar out of line with the
other. Cell warnings will manifest within this period of time and the diver
will begin to get audible and visual alarms ...task loading increases.
The voting system is not about "which one is
more than .2 bar out of line with the other". A quick read through the
manual will tell you this.
The unit alarms if it senses a PO2 over 1.6,
which is a good thing. Problem with this is that many of the divers will run
100% oxygen at 20 ft, which is a PO2 of 1.6, if they drop below the 20 ft
they get an alarm, fair enough.
Anyone decompressing on O2 mode at 6m will
find it incredibly difficult to achieve 100% FO2. They will also do the same
as OC divers on pure O2, and make sure they don't go below 6m/20ft.
Weight must be placed on the top of the
rebreather in order to balance the trim.
Weight must be placed on ANY diving system
for correct trim.
If divers put to much gas in the counter
lungs the upper body is lifted and trim is then off center.
Putting too much gas in the counter lungs
can cause problems, in the same way that too much gas in a BCD or drysuit
can. So don't put too much gas in.
Many divers use the Inspiration to extend
their times in open ocean, this in itself may pose problems. If the
decompression gained by the increased bottom times is met with undesirable
conditions such as rough seas it is not so easy to adjust buoyancy as with
breathing open circuit.
This is why rebreather courses drum into you
the concept "You are a novice again" and insist you build up your experience
slowly. By the time you take a CCR into rough seas, you should be capable of
dealing with them.
Many of the buoyancy characteristics
involved with rebreathers require a longer learning curve and must be
anticipated, if the diver is not up to par they are much less forgiving than
OC. If the constant PO2 is increased or decreased too quickly due to
unforeseen circumstances the diver could quickly become hypoxic/hyperoxic.
This is just wrong. It's like someone
worrying about technical diving because manifolded twinsets can inject pure
argon into your breathing system.
Mouthpiece does not have OC bailout built
into it, bailout is a time of increased stress so it is pertinent the
transition should be smooth without chance for a mistake.
The reasons for me coming off-loop are
because it's flooded (with the attendant risk of caustic cocktail) or
because I've chucked into it. In either case, the mouthpiece is not viable,
so I don't *want* it to be part of my OC bailout.
The CCR mouthpiece has to be effectively
closed before the transition to OC bailout is performed or it will flood the
breathing loop making the diver negatively buoyant.
This is common to all rebreathers, even the
RB80, and is a basic skill.
If the O-ring on top of the cartridge lid is
dirty or not aligned properly CO2 will take the path of least resistance and
bypass the carbon dioxide scrubber therefore breathed back into the loop.
Hypercapnia begins and the diver is faced with another problem to solve.
This is why the pre-dive checks include
making sure the O-ring IS clean.
As the diver descends they must equalize the
counter lungs, if this procedure is not adhered to and they begin an
uncontrolled descent the lungs collapse and the diver is not able to breath,
an automatic diluent add is an aftermarket product which does combat this.
But since we are talking factory here the diver is faced with equalizing
counter lungs, ears, sinuses, mask drysuit, BCD, monitoring PO2 on handsets,
buddy position, light and depth in the water column. It has been mentioned
before that this is "a busy time".
Out of the list "lungs, ears, sinuses, mask
drysuit, BCD" counterlungs are the only thing there an open circuit diver
doesn't also have to worry about. And rebreather divers don't usually use a
BCD, so it's a straightforward exchange of one bag of gas for another.
Inspiration does not have SS backplate and
utilizes many plastic fastex clips, which some view as failure points. There
are seven quick releases on the soft harness including the crotch strap and
handset clips. The clips that hold the yellow casing lid on the unit break
frequently so spares are required as well.
Frequent clip breakage is not a complaint
voiced by any of the people who actually dive the unit.
Often difficult to transport with Sofnolime,
if you do not have an MSDS on your person you will be declined, even if you
do have the Material Safety Data Sheet on hand and the handler does not feel
comfortable with the issue they will not let the scrubber material on the
plane. Most Inspiration divers seek out `Inspiration friendly dive Centers`
so they are able to obtain the wide array of parts required to service and
Divers seek out Inspiration-friendly centres
so that they can hire cylinders and buy lime on site, rather than having to
pay for extra baggage allowance.
The oxygen sensors are proprietary to the
Inspiration, which limits the diversity on this product. Many of the CCR's
will allow various types of sensors to be used but not so the case with
Inspiration's and it is strongly voiced by Martin Parker.
The R22-BUDs are the only cells to have gone
through the testing process, so they're the only cells approved by APD. Many
divers use equivalents, but this leaves their units effectively untested, so
it's on their own heads. The reason other CCRs allow various sensors is that
*none* of them have undergone the level of testing that the Inspiration has
- in effect, they're all at the "untested" stage.
Patrick Duffy with Oxycheq in the US sells
similar sensors and says there is absolutely no difference between the
Teledyne's he sells and the Inspiration sensors.
There probably isn't - a number of people
run the R22-Ds with no problems. However, "probably" is all we can say - the
R22-Ds have not been formally tested in the Inspiration, so they're not
recommended. Where's the problem with that?
Scrubber canister is small (2.45 Kg of 8-12
mesh, 797 diving grade sofnolime) and does not facilitate the use many of
the mixed gas Inspiration divers put it through. At depth CO2 breakthrough
is rapid even with a resting diver, if breathing resistance is elevated the
scrubber is near void. With increased CO2 build up the diver is of course
exposing oneself to further malady. Diving high helium concentrations assist
with this problem as it is less dense than air, easier to breath therefore
less CO2 buildup and the scrubber should last longer but it is playing on
the edge. High PPN2 should be ultimately avoided.
The scrubber will last three hours. The
problems he lists above will only arise if you try to push the scrubber
beyond its rated life. So don't push it.
If counter lungs are not situated adequately
they will float above the divers shoulders and increase breathing
So situate them correctly. It involves
pulling one piece of webbing each side as you kit up.
The LP hoses which feed the diluent and the
oxygen inlets on the counter lungs use a different end than the BCD
This is correct. The reason is explained
further down in the same paragraph:
The reason the end is different on the BCD
inflator is to supply a greater amount of gas to the Auto Air regulator used
as a bailout/inflation device.
This Auto Air is prone to free flow
situations and can dump the diluent gas if not tended to quick enough.
Service the device at reasonable intervals
and it's bomb-proof. Fail to service it, and it behaves like any other
unserviced regulator. And with this particular regulator, the manufacturer
not only supplies parts to anyone who asks, they supply the service manual
as well (FOC last time I asked for one).
Most Inspirations divers discard this Auto
Air early into their CCR career.
No they don't.
If both handsets shut off in the water the
diver is faced with a series of questions in order to `reboot` the system.
One of the questions ask if you would like to calibrate `yes or no` if the
diver is stressed and chooses `yes` they will effectively be adding 100%
oxygen into the breathing loop no matter what depth they are at in the water
So don't shut off both handsets in the
water. In the extremely unlikely event that you do, the only questions you
have to answer are "Dive now?" (to which you answer "yes", of course) and
(on earlier units) "Calibrate?" (to which you answer "no"). Current units
won't even ask the second question.
If the battery is low it will not supply
enough EMF for the oxygen solenoid to open the valve and add life sustaining
EMF is Electromotive Force - more or less
synonymous with "voltage". He's wrong actually - it's current that drives a
solenoid. But that's by the by - you get plenty of warning of this sort of
thing happening (about a week unless you're in very cold water, in which
case just a couple of days), and you've got a spare battery in the other
handset to take over when it's too low. And if that one's flat as well,
you've get enough life in the handset to switch to manual mode, where the
solenoid isn't needed at all.
The control handsets are secured to the
canister via rubber hose, the wiring is run through this conduit down to the
electronic handsets that are monitoring the dynamics of the oxygen sensors.
These rubber conduits enter into the scrubber/O2 sensor compartment where it
is humid and if not perfectly sealed will allow condensation to migrate into
the hose and wreak havoc with the electronics in the handsets.
No it won't.
I'll close with a quote from earlier in his document - "I will waste all of
your time with this one"