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.

Page 2

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.

Page 4

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).

Page 6

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.

Page 8

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.

Page 10

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

support@opensafety.eu or sales@opensafety.eu 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