Apocalypse Newsletter #5 - Open Safety Equipment Ltd · 2016. 10. 4. · Apocalypse Newsletter #5...
Transcript of Apocalypse Newsletter #5 - Open Safety Equipment Ltd · 2016. 10. 4. · Apocalypse Newsletter #5...
Apocalypse Newsletter #5
On behalf of OSEL in this Newsletter I will address:
EA shipping date - I can now give a date at last: 30th October 2009 or earlier
1. All CE tests have been carried out and have been through at least one pass of audit.
OSEL is not aware of any performance issue: it is purely paperwork and procedure.
Audits of the documentation and additional tests are still ongoing though.
2. If formal CE certification is not received by 30th October, then all customers outside
Europe will be offered shipment from the USA with the warranty that any CE non-
conformance found subsequently will be corrected free of charge. All CE test data and
documentation will be published so customers can make an informed decision.
3. Outstanding problem production components:
a. VIPR O2 regulator (Rejected by Deep Life repeatedly on their inspection due to
not being as per spec, reported in #4). The first shipments will be with an
Apecs DS4 regulator and a valve, fitted to the internal cylinder. Deep Life is
taken over design and production management the VIPR (Valve with
Integrated Pressure Regulator) due to these QA issues on the stock received.
We have much more confidence in Deep Life than in the existing VIPR supplier.
b. There may be odd shortages if any other parts are rejected on assembly or
during factory unit wet testing on completion of assembly. If this occurs
customers so affected will be notified and advised of the way forward.
By 7th October, all customers for the oxygen rebreather will receive a document giving the format
that will be shipped, and the choice of taking that, or waiting. The Apocalypse iCCR customers will
get a similar choice later in October.
ALVBOV and Pods, Film
A film production company is producing a training film of the ALVBOV and pods for us. It will be
mounted on the OSEL server during October. This film explains the options being offered (ref
above).
Frequently Asked Questions
These questions are taken from posts onto Rebreatherworld.com addressed to me:
OSEL_Paul or from direct queries answered by my staff.
1. What is the policy/training for ascents, full bailout and stay off the loop till
surface or bail off loop and back on after a short time then begin ascent.
The training for ascents is full OC ascents, to validate to the diver the ‘true’ quantity of OC
gas needed to bailout from a CCR dive.
The OSEL policy for ascents is that these are done on OC; the recommendation is that if
ascents are not done on OC then the PPO2 be monitored constantly.
2. How long is the service interval? IMHO 14 months would be good to give some
slack.
The service interval is annually; however there is 3 months slack so the service interval could
be as much as 15 months provided your oxygen cells are within date.
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3. What happens if you don't service the unit? Does the unit warn you, stop
working, or work in OC mode only?
Every time you calibrate, you see the warning of the duration until the annual servicing is
required on the buddy display. Once the servicing interval is exceeded, the iCCR will not
allow you to select CC mode, though if charged, will still monitor PPO2 when submerged
whilst warning you that it needs servicing and logging the fact.
4. In the last newsletter you talk about a one-way valve+connector assembly in
answer #3. Can this be used as a quick disconnect? I have plans to use side mount
MUG and bailout tanks only and remove the rails on the side of the housing. For this
I need a way to disconnect them from the unit.
No, the MUG to Bailout Manifold is a semi-permanent LP 3/8 UNF threaded hose that screws
into ports of the regulators, that are otherwise blanked off.
OSEL or for that matter Deep Life who designed the Apocalypse are strongly against the use
of Quick Disconnects on any oxygen line. If used on the Apocalypse oxygen supply, a Quick
Disconnect could be lethal, as if disconnected the diver will still get positive feedback that
oxygen is on.
OSEL and Deep Life are both against quick disconnects generally on any LP/MP/HP hose due
to the failure modes associated with these.
What you are suggesting in removing the side rails and side mounting all of your MUG/bailout
gas was not a design criterion of the unit as a recreational rebreather and is not officially
supported as a means of rigging it to dive. The side rails or metalsub brackets also protect
the rebreather in transit.
The Apocalypse Type IV requires an appropriate amount of gas for your dive profile in the
MUG cylinder carried on the side, which is what the ALVBOV is directly plumbed to.
5. You have a light sensor on the PO2 pod. How much light does it need? How can
you verify you have had the pod in light long enough? I dive a lot after sunset and
only use a small led light during gearing up.
Calibration is not required on every dive, but should be carried out daily. The light sensor is
for calibration of the oxygen cells, and any normally lighted room or daylight is sufficient.
Once the PPo2 pod is calibrated it gives positive indication of this.
The light sensor has nothing to do with the unit being switched on: this is automatic on being
using in CC mode and even if not re-calibrated prior to a dive then the old calibration settings
are retained.
The Apocalypse benefits from the design of its sister, the Incursion eCCR which is designed
for use in a tactical environment and can be fully run through the pre-dive sequence by
touch, with just a red-light to see by if required, to complete the supervisors checkoff list.
With our iCCR, you also have the light of the PPo2 and CO2 Pods to see by, which should
assist in gearing up and also in your being located in-water at night.
6. How long is the battery life of the CO2 and PO2 pods and ALVBOV?
It is typically 32 hours or 10 dives, however in standby between dives the unit can be left for
weeks without being recharged. It is recommended to recharge the pods and PFD during the
pre-dive setup process.
7. Does the CO2 pod use the ppCO2 limit of 6.5kPa for both CO2 retention and
scrubber breakthrough? Is the minimum ppCO2 value during a breath cycle the
same as CO2 content after scrubber?
Yes, if the exhaled CO2 reaches 6.5kPa, then you will be bailed off the loop: this can occur if
the scrubber breaks through, a mushroom valve fails or the diver is retaining CO2.
If the gas is measured after a functioning scrubber, it has minimal CO2 content on average,
certainly not enough to measure in a usable manner with the spiking that can occur resulting
in a lot of false positives for inhale based CO2 alarms. The normal minimum PPCO2 value
exhaled during the breath cycle is 3.5-4kPa, which is measurable and is what we display on
the CO2 Pod.
8. The newsletter (and Manual) refers that the EACs must be disposed of if used
once and left for 2 weeks. What is the risk of the EAC being used after this point if it
is bagged or left sealed in the unit. – i.e. deterioration, bacterial, risk of not sealing
bag etc. Is it a case that testing beyond this 2 week period has not been done?
Not quite correct: an EAC can be used multiple times in any 14 day period, but once 14 days
has been reached from the time of opening of that EAC, or 2 hours 45 minutes of diving has
been carried out, it should be replaced. After two weeks, results start to be more variable,
and there is also a risk the seals around the EAC can develop a set to them.
The O.R. EAC testing has been carried out using EACs that had been in storage for 5 years
from date of manufacture.
9. Another observation is that the pfd is activated upon pressing the O2 add. In
diving practice are you finding that the divers end up giving a small "squirt" of O2
as they feel appropriate in order to activate the display after they get used to the
unit. I would imagine that after a while you would get fairly tuned in to how hard
to press the button and for how long?
Essentially yes, this was a factor designed into the iCCR’s PFD and it works well when the
diver is exercising. When stationary in the water, this may raise the PPO2 a tad too high, so
it is safer in these circumstances to instead press the PFD every couple of minutes.
10. Where exactly is the (PFD) button seated and what kind of pressure do you
have to apply? Could you maybe trigger the PO2 checks by pressing the BOV
against your camera housing, or are you forced to use one hand?
The primary PFD button is located on the top front of the ALVBOV,
in yellow in the image below. It uses an infrared sensor, and there
are no metallic springs to corrode.
Light finger pressure is enough, with practise a strobe arm/camera
handle might work but this hasn’t been something formally tested
so far, as divers usually have sufficient fingers for one to be
available. The button area is large to allow divers with dry mitts in
very cold water to operate it.
Manual O2 add is ergonomically located at the divers waist,
requires about 1kg of pressure to activate and has tactile
feedback: a completely difference response when gas is applied compared to when gas is off.
11. Is it possible to choose having the PPO2 controlled/checked in an automated
way every 1 minute? That would definitely let the diver(s) know their PPO2 hands-
free if they choose to every minute. Since the control/check is audible, then this
would actually acts as enforcement to the golden rule "Always know your PPO2".
The option can also include CO2 monitoring option. In my opinion, this should be a
key safety feature since the design of the unit has adopted new safety factors into
considerations in order to reduce/eliminate fatalities.
No, what you suggest will not be an option as there would be no confirmation that the diver
is actually paying attention and honestly knows their PPO2. The safety engineers who have
audited the iCCR as a functionally safe design to EN61508, concluded that based on accident
data and HAZOPs there is a definite safety requirement to check that the diver is actually
monitoring the PPO2, and to provide warnings then bail out if he is not.
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12. Why are you waiting for other manufacturers for the dive computer? A wrist
display is an additional safety device. IMHO you are already doing more than
enough by releasing the technical requirements. If your unit is working you should
immediately market it after APOC shipment!
As per newsletter #4, the OSEL wireless wrist computer will be released only once both the
Apocalypse iCCR is shipping smoothly and reasonable opportunity has been given to other
respected dive computer manufacturers to bring out Apocalypse iCCR wireless compatible
designs to allow fair competition with a diverse user choice. In truth, OSEL would like to
release the dive computer immediately but Deep Life decides the timetable on this and has
wider safety and strategic objectives.
There is no timetable at all for the release of the OSEL wireless computer: Deep Life will
release this to us when appropriate. It is not required for diving the Apocalypse iCCR and is
simply a complementary option that will be equally as usable for Open-Circuit mixed gas
diving or with any other CCR in standalone mode.
Deep Life has the electronics developed and EMC approved: the independent EMC report is
on their web site. However, they report that software verification is not complete - the
software is in MISRA C just now, and they wish to rewrite it in SPARK ADA as part of their EN
61508 work. The rebreather, Pods and PFD already have their core in SPARK ADA.
13. The Apoc is not delivered with any MUG/BOG-cylinder(s) right?
That is correct, just the integrated 2L 207bar oxygen cylinder. The valve for the MUG
cylinder is part of the standard package, so it just needs to be fitted to whatever size of MUG
that fits the type of dives you do – normally 2 litre, but test divers have used everything
from 1 litre to 12 litres.
14. From the material presented it looks like it can accommodate quite a range of
cylinder sizes (~2-12l on both sides). I cannot find any cylinders in the Open
Safety web shop, so is it entirely up to the user to find cylinders that suit him?
Yes.
Shortly the 2L oxygen cylinder and VIPR valve will be available for purchase from our web
shop as a spare component.
15. How does this flexibility of cylinder choice work with the ambitious safety case
for the unit if the choice for MUG/BOG-cylinders with valves is completely outside
of the manufacturers control?
Safety is not compromised because:
• To ensure that the diver can reach the valve for the MUG cylinder as designed, a top
quality cylinder valve for the MUG cylinder is included with every order.
• Cylinders over the range 1 litre to 12 litres can be fitted without affecting the ability of
the diver to access that valve.
The reason for this decision is that dives use a variety of different Make-Up-Gas cylinders –
both because some dives need more Make-Up-Gas than others, and because the practicalities
of travel - especially the US TSA who unlawfully take cylinders with valves fitted (common
law in Europe regards it as theft if items taken from baggage are not recoverable by the
owner). As a result many divers rent cylinders at their destination, and the OSEL cylinder
policy reflects that.
16. Also there does not appear to be any provision for an emergency gas source for
a buddy, right? Like an octopus or so. It looks like the idea is that the diver should
always use MUG/BOG that is "hardwired" to the rebreather (no QC's). So if the
diver adds a hose and some kind of second stage to the MUG/BOG as an alternate
gas source, does that not affect the safety case of the whole unit?
The Apoc Type IV iCCR does not ship with an alternative bailout gas source included, this is
up to the owner. The reason for this is that none of the Octopus rigs appear to meet
European regulations (first stages meet EN 250 with one second stage, and fail with two
second stages). We understand Octopus stages are very widely used, and we anticipate
many divers will fit them to their bail out gas, but their performance causes us problems in
shipping them as part of a CE certified product.
Bailout needs to be appropriate for the diving being conducted and is available for purchase
from any LDS. This topic will be covered during an approved Apoc training course.
Whilst appropriate bailout in all respects is expected to be carried on a dive by the Apoc
diver, the actual style and type of bailout has to be chosen by the diver after proper dive
planning and risk assessment.
17. What is the procedure for "multilevel" ascents? Like on reef dives or so when
the ascent is slow and more like a part of the dive. Still all on OC, or do you
recommend going back and forth between OC/CC? How about dives with a lot of
decompression? Do all the deco on OC or switch back to CC for the stops?
This topic will be covered by your iCCR training instructor on course, including the
precautions to take before switching back onto a rebreather after having bailed out: this is a
hazardous manoeuvre that needs training and verification that it is being done correctly.
18. What sensors does the Apoc (iCCR) have? What I have read about so far: O2,
CO2, He, pressure, temperature, light, respiratory level (rapid temp sensor),
ALVBOV-position and radio-transceivers. Did I miss something?
1 x CO2 sensor. We have tried to keep the false alarm rate low by masking out the sensor
when it fails, and ensuring it fails in a known state, but there will be some false alarms in
unusual conditions. A simple one we found is if the diver holds his breath for too long.
3 x O2 sensors with digital temperature compensation, with gold SMB connectors for
reliability and corrosion resistance. The sensors tolerate water on their rear surface: there is
a gel on them similar to that used for engine sensor electronics. The sensors shed water
(there is no well around the membrane). The sensors are mechanically strengthened
compared to contemporary sensors.
1 x Helium sensor in the CO2 pod to validate the Make_Up_Gas contents and compensate the
helium sensor for noble gas spectral broadening.
1 x Light sensor in the PPo2 Pod for semi-automatic oxygen calibration using air for accuracy
and ease of use.
1 x Relative Humidity sensor, used for compensation of other sensors.
1 x Pressure sensor in the CO2 sensor pod
9 x temperature sensors (one in the CO2 sensor, one in the pressure sensor, two next to
each oxygen sensor, and a fast acting temperature sensor in the ALVBOV right at the
mouthpiece to detect the respiratory rate and the start of exhale for CO2 end-tidal.).
1 x infrared sensor in the PFD button
2 x Hall sensors in the ALVBOV to detect its position
3 x DASH7 transceivers (in CO2 pod, O2 pod and PFD).
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19. Does Apple know you are "borrowing" their Iphone battery icon for your screen
mock-ups (pg 9 #4)? They are pretty humourless about those sorts of things, I
hear.
Just to clarify: the images from the last newsletter were screen dumps and not mock-ups.
However, this time I will use icons from the source files simply because it is more convenient
for me.
In fact, there are a lot of different icons displayed on the pods, none of which are exactly the
same as found on an iPhone. A few more are shown below: the large ones alternate between
the icon with its warning message, and the value reading a diver expects from that pod (e.g.
PPO2).
Diver not monitoring PPO2 General warning Fast respiration
RSSI (Received Signal Strength Indication, in dBm) Helium fraction.
No dive Hot scrubber exhaust Flood
Returning to the Apple question, this type of battery symbol pre-existed its use by Apple.
There are many similar icons, such as on http://www.istockphoto.com/stock-illustration-
9914139-battery-icon.php and the legal position is outlined by a US lawyer on
http://rychlicki.net/en/2007/04/01/174/. However, we do not support plagiarism, and in
light of your comment implying plagiarism have had the icon replaced even though it differed
from the Apple icon in some details and the iCCR battery icon changes colour as it is
discharged: 75% to full is green, 45% to 74% is yellow, 0 to 45% is red. You will have to
wait for the pods to see the new one – it is not worse than the old one.
20. Are there any plans for upgrades to be available from the manual APOC to any
future full eccr model that may be released?
The capability for a functionally safe fully eCCR rebreather does currently exist, and is
available from Deep Life through other clients of theirs, commercial diving and military
diving. However, Deep Life developed the Apocalypse on the basis of how sports divers use
their equipment – this is very different from commercial and military diving, so what they
conclude as the safest design for sports divers differs substantially from the military units, in
particular in the iCCR concept rather than eCCR.
There is a desire in Deep Life to understand what is needed for a safe eCCR for sports divers.
To progress those aspirations, there is 12GB in total of logging in the Apocalypse monitors
(196 parameters every second), storing for a year. Deep Life intends to use that data to
make safer rebreathers. That data will be used to develop a SIL 4 sports eCCR. Deep Life
have stated that it will not release a sports eCCR unless it achieves SIL 4, and this sort of
data analysis is part of the path to that end.
If it is proven that a functionally safe eCCR is indeed a safe option to offer for recreational
diving, this could be offered as a plug-in replacement for the iCCR dumb scrubber head or
even via a wireless variable orifice oxygen addition module offering a hybrid mode to the
iCCR.
21. Why have 2 water dumps? -
Surely the introduction of 2 dumps
is excessive and could lead to more
problems than they solve i.e. leaks
etc. Why was it decided to have 2
since the back up to one of the
water dump cords breaking is to
bailout?
The Apoc Type IV CCRs have one water
dump per counterlung, and 2
counterlungs. The dual water dumps
allow simple draining of a fully flooded
loop, allowing the dive to continue as
the water naturally collects at the
bottom of each counterlung. They also
greatly simplify washing the equipment.
The water dump cord breaking is
assessed as minimal, and if it does, it
does not compromise the diver – all it
means it that water dump won’t dump water. The equipment does not need water dumps at
all to allow it to be dived.
Water dumps have some other functions: an Over Pressure Valve is fitted to the exhale
counterlung to prevent fast ascents with a sealed loop rupturing the unit. The OPV vents
before the bags will rupture and is of a high flow design. Water dumps provide a further gas
exit port in an overpressure situation. The same test as applied in EN1809 for BCDs was
applied to the counterlungs, but with the ALV on purge to inject gas.
Automatic water dumps were found both by formal modelling and in manned trials, to be
unusable because the pressure differential needed to actuate them fights the pressure
differential to trigger the Over Pressure Valve. Manual dumps were then included, located at
the bottom of each of the counterlungs. The water dump is a 30mm diameter and requires
between 1kg and 1.5kg to actuate it, so it will not trigger automatically.
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An extended review of the water dumps considered whether these should be single or double
valve design. With a single valve dump pulling the dump opens the breathing loop. With a
double valve, water ingress to the loop is prevented by use of a second flapper valve. All
Deep Life designed rebreathers, including the Apocalypse, use a double valve.
From the FMECA for the Apocalypse, the hazards of a water dump are:
• Stuck open. Our two Training Managers, Paul Haynes and Gregg Stanton, indicated that
a double valve dump was strongly preferred, and that the isolation of the causal event
and the manifestation of the failure should the dump be pulled, is less of an issue than
water ingress to the loop.
• Stuck shut. This can be caused by breakage of the pull cord, or the pull cord coming
away from the pull toggle. The hazard is mitigated by their protected location, and the
use of two water dumps, only one of which need operate.
• Slow leak. This is a subset of stuck open.
• Entanglement. This is mitigated by their protected location and the choice of pull dumps
that are of a low snag design: a pear shape instead of a ring or hoop.
Each counterlung water dump has a second umbrella valve fitted to prevent water ingress.
These are colour coded red and green for exhale and inhale counterlungs respectively. If a
field failure of the main one-way valve occurs, the diver can save the dive trip by using the
correct colour-coded water dump mushroom.
As well as the two water dumps, one at the bottom of each counterlung, a third water dump
is provided in the ALVBOV to prevent water collecting in hoses. This uses a one-way valve
and a manual press button to activate. The ALVBOV water dump has the one-way valve on
the outside of the ALVBOV and the button on the inside path: the opposite to that used for
the counterlungs. Incidentally, the ALVBOV also has a second Over-Pressure Valve: it vents
at 50mbar to 80mbar, compared to the main Over-Pressure valve which vents at 35mbar –
this uses the lip seal design of the ALVBOV and has no extra components.
22. I also notice that OSEL does not appear on the exhibitors list for the October
dive show at the NEC Birmingham. I thought this would be the first opportunity to
show the unit and sell a few from the stand! Worrying?
OSEL do not appear on the list of attendee’s at the October dive show at NEC as we have
never had a stand there, nor do we plan to attend this year. The Apocalypse O2-CCR was
first shown in the UK at NEC in 2008 in support of Narked At 90’s eCCR head, functionally our
O2-CCR product remains the same with only cosmetic changes in the past year.
Production Apocalypse iCCRs some of which will have had a few hours on them, will be at
DEMA in Orlando, Florida where we will be represented on booth #204.
23. Is the CE-certification/rating/approval or whatever it’s called for the whole
system still valid if the individual diver adds critical components at their own
leisure?
Certification for the standards that the Apoc TypeIV CCR has been audited to, will be as per
the configuration that it is shipped to customers. Provided that the product is not modified
from standard as supplied, then the certification to CE remains.
What this mean to an Apoc diver with regards adding critical components is: they can use
any inverted cylinders appropriate to the dive, for both MUG and bailout up to 12L 300bar on
the side rails mounts (or using MetalSub brackets), any suitable bailout regulator(s) and 2nd
stage(s) that meet CE standards. If bailout is side mounted or side slung as a stage, then
this can be anything that the diver considers as suitable based on their applicable training for
the dive in question.
If the core rebreather product/design is modified in any form, from what is supplied as
standard: examples of what is strictly NOT recommended includes fitting QC’s or inline
shutoff valves between either the MUG and ALVBOV or oxygen cylinder and manual add or
replacing the manual add with a non tested aftermarket option such as one that combines:
oxygen, diluent/Make-Up_Gas and off-board gas addition together. These particular
modifications are potentially lethal, and if fitted means the product is not safe to dive, in
Europe or anywhere else.
Only accessories specifically authorised by the Design Authority and manufacturer that have
a CE certification may be used with this equipment.
Where a connection is made to this equipment, the certification should state clearly that it is
certified for use with this product. The Design Authority and manufacturer approve only the
configurations described specifically in the Apocalypse manual.
24. If a diver is packing for air travel and thus renting cylinders at their destination
to keep excess baggage charges to a minimum - will the ALVBOV with hoses and
the pods all fit in the space in the case that is normally occupied by the 2 litre
oxygen cylinder?
The recommendation is that the Pods and ALVBOV/PFD are carried in carry on baggage in
their soft case.
Where this is not feasible, then yes with the O2 cylinder removed it is feasible to carry the
electronic pods that way suitably protected in say bubble wrap or neoprene. If so, to protect
from shock damage and potential exposure to temperature extremes it is recommended that
the oxygen cells are still carried in hand luggage. Most oxygen sensors fail permanently if
exposed to temperatures of more than 50C, and these can happen easily in baggage left in a
car, or on a cart on a hot runway.
25. Will the ALVBOV fit the open circuit pod of the KM48 full-face mask? There was
mention a fair while ago of there being plans to offer adaptors etc for several
different FFMs but I have heard nothing since
Deep Life is still working on FFM fittings for the ALVBOV, in conjunction with several FFM
manufacturers.
26. Why use SMB cells instead of Molex, because Molex, when correctly use, are
more reliable and you can easily replace one yourself if that would ever be needed
or am I missing something? I have been told a correctly fixed Molex, gold plated, at
least on the contact surface, (using tinned wire, or silver coated wire), then
crimped correctly, and soldered, will give eternal contact, this is not the always the
case with the SMB: they do not always have perfect contact, much more fragile (the
little small pin in the middle), less dirt resistant etc
This is nonsense.
SMB will always be more reliable then Molex connectors when designed in correctly, by
simple engineering concepts. Molex is a single wiping contact; the SMB is a multi-leaf
bifurcated contact. Bifurcated contacts are always more reliable than single wiping
contacts.
However, if a user physically damages the SMB connector that is a different matter. The
damage is normally the outer leaves move apart because the user puts in the cells at an
angle: hence a cell holder is needed, and we also add two o-rings to keep the leaves
together and prevent this damage.
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User experience is the SMB is more reliable: see the discussions on that from people who
have changed over to coax from Molex on Inspirations, and they have no o-rings or
holder, - even despite that are more reliable.
The reason that only one mainstream rebreather manufacturer other then OSEL makes
use of the benefits of the SMB connector, in Europe at least, is that the Teledyne
distributor in Europe, Vandagraph, has an anti-competitive policy that restrict sales of the
R22 SMB oxygen cells in commercial quantities to just one manufacturer, even though that
manufacturer did not originate it, and other manufacturers do not have the buying volume
to get SMB terminated oxygen cells direct from AII or Teledyne. We do have the buying
volume so we do not buy from middlemen.
The OSEL oxygen cells make use of SMB connectors that are custom designed for us to be
very much more robust, and water tolerant than other sensors.
27. Although the diver may not detect any CO2 symptoms as they begin to rise
above 5mBar, should a dive be wrapped at this CO2 level? Is it true, that CO2 levels
of 15-20 mBar are capable of inducing unconsciousness in a diver, and therefore
that a 10mBar threshold on the inhale side is a realistic bail out alarm level?
Neither the PPE Directive nor EN 14143 prohibits a manufacturer from providing sound safety
advice for their products. The EN 14143 limit for scrubber breakthrough is without any
scientific basis and is dangerous for divers because the 5mbar limit causes no discernible
physiological effects. This means that divers in the “real world” extrapolate the CE 5mbar
figures to the “real breakthrough limit”. There are literally thousands of reports of divers,
using CCR scrubbers at a multiple of their 5mbar limit as published by manufacturers for
their rebreather. The safety advice to the diver of the 2kPa (20mBar or 2% SEV) limit by
OSEL ‘s publication of 2KPa figures addresses this specific risk.
Unlike the 0.5kPa (5mBar) limit, the 2kPA limit is based on solid scientific evidence. A study
entitled “Physiologic Basis for CO2 Limits Within Semi-Closed and Closed Circuit Underwater
Breathing Apparatus” by M. Knafelc, NEDU Document TR 4-00 concludes:
The D. E. Warkander NEDU study, entitled “Comprehensive Performance Limits for Divers’
Underwater Breathing Gear Consequences of Adopting Diver-Focused Limits”, Jan 2007,
NEDU Document TR 07-02 provides further and strong scientific confirmation of Knafelc’s
conclusion. A copy of TR 07 was also provided with the “Safety Case Supporting Material.
The author of the largest single scientific work on physiologically based CO2 limits for divers,
Dr. Dan Warkander of NEDU, was asked about the 2kPa limit and confirmed that other than a
30% increase in the diver’s respiratory rate, there are no other symptoms at this scrubber
breakthrough level.
These studies were provided to SGS as part of the Technical File for the Apocalypse and its
effective conclusion is as below.
“The EN 14143 CO2 limit of 0.5kPa was the result of advice from one person when the
standard was written, with no scientific evidence to support it. Since that advice was given,
many divers have died from hypercapnia on recreational rebreathers.
OSEL quotes physiologically validated scrubber duration, based on the recommended and
quoted maximum depth that the rebreather is designed to be dived to. Deep Life regularly
reviews those limits.
As both the CE 0.5kPa limit and the safe 2kPa limit are given to the maximum recommended
dive depth of 80m (262ft), the Apocalypse meets the requirements of EN 14143 and as the
advice is clearly safe, it meets the PPE directive.
It is submitted that providing a 0.5kPa limit on its own is unreasonably dangerous as it
leaves the diver to guess the true scrubber duration, especially when diving at a greater
depth then that of the scrubber duration, measured at 40m (131ft) as required by EN 14143.
The accident record gives evidence that this is exactly what divers have been doing, and
sometimes getting it wrong because of lack of data. The testing of the Apocalypse Scrubber
for duration is available from http://www.deeplife.co.uk/or_dv.php inclusive of the fully
independent test results published by Micropore from their own test facility.
This should cover the OSEL applicable questions from the last months’s “mail bag”. I will
continue to review RebreatherWorld and also repeating questions on our support lines at
[email protected] or [email protected] for my next newsletter. My next newsletter
will be next month, when we ship customer units.
Those interested in purchasing the Apocalypse either in O2-CCR or iCCR versions can do this
directly from our webshop www.opensafety.eu
Paul K, 24 September 2009