TDI Evolution Closed Circuit Rebreather Diver Course by BorneoDream.com Billy Hammond #10407 - 2007

TDI Evolution Closed Circuit Rebreather Diver Course by

BorneoDream.com

Billy Hammond #10407 - 2007

Overview of Course Structure• 1 - Introduction and Welcome• 2 - The History and Development of Rebreathers• 3 - Mechanics of the inspiration and Evolution• 4 - Classic Electronics Control (Optional)• 5 - Vision Electronics Control (Optional)• 6 - Physiology - A Reflection for the CCR Diver

TDI Inspiration and Evolution Closed Circuit Rebreather Diver

Course

• 7 - Let’s Go Diving the Rebreather - Preparation• 8 - Let’s Go Diving the Rebreather - In the Water• 9 - Avoiding Rebreather Incidents - Safe Diving• 10 - Mod 2 Extension (Optional extra course)• 11 - Mod 3 Extension (optional extra course)

Overview of Course Structure continued

TDI Inspiration and Evolution Closed Circuit Rebreather Diver

Course

TDI Inspiration/Evolution Family of Rebreathers Divers Course

Section 1:

Introduction and Welcome


• Congratulations of enrolling in a most thrilling experience with Inspiration/Evolution technology

• Welcome to a new way of thinking about diving• Understand that you are ALL novices again • You will develop new skills for CCR diving

including:– Attitudes– Disciplines– Awareness


Who the course is for and what you can expect to get out of it.

• COURSE PREREQUISITES– 18 years of age– Logged 100+ dives– Nitrox and Advanced Nitrox training

• COURSE CREDENTIALS– To become qualified to dive the Inspiration/Evolution family of

rebreathers on either Classic or Vision Electronics or both (double certification and extra dives) on Air Diluent up to 40m/132ft with safety stops and 5 minutes max deco at 6m/ 20ft


• Why CCR Diving– Longer dive durations possible with very

little equipment– Almost silent and bubble free unless

ascending– Extremely efficient use of breathing gas– Optional Nitrox mix for all depths according

to user-selectable PPO2 setpoint– Warm and moist comfortable breathing gas

reducing risk of hypothermic tendencies

Introduction and Welcome• What else can you expect to experience on this course?

– Many new terms for CCR not used in OC or SCR diving

– Change from a constant percentage Nitrox mix in OC to a variable percentage Nitrox mix with constant partial pressure in CCR mode

– Computer controlled gas injection system on ascent causes accelerating bouyancy characteristics

• We need to think differently

– Jump a billion years of evolutionary development• An opportunity to almost evolve into a sea-going mammal

with hours of sub-surface capability, and be back on land again for another fun filled experience


Section 2:

The History and

Development of Rebreathers

The History and Development of Rebreathers

• Rebreathers in basic form have been around for over a century underwater, and longer for mine rescue work

• The earliest makes were pure oxygen devices

• The Englishmen Henry Fleuss achieves a major milestone covering over 300 meters (1000 feet) underwater in the construction of the Severn railway tunnel a century ago

• Military rebreathers developed and used-Stealth


• The advent of readily available Nitrox to the recreational market fuelled the development of recreational nitrox SCR rebreathers

• Progress and need in the military theater saw the development of a number of electronic controlled CCR machines over the last two decades

• Some cave divers opted for passive mechanical SCR with no electronics

• Makes include the Electrolung; Cis Lunar; Drager Atlantis, Dolphin and Ray.

• We see the advent of recreational CCR’s with the Inspiration in 1997, followed by Prism, Megalodon, Ouroboros, Optima and Kiss, and in 2005 the Evolution


CONCEPTUAL REBREATHER DESIGN

• All need a scrubber for CO2 removal

• Pure Oxygen rebreather – no need for electronics in basic form just keep manually adding gas when loop volume falls

• Semi Closed SCR uses a known nitrox for loop addition

• Mechanical rebreathers use a fractional volume technique to refresh gas

• Either Passive by sucking in fresh gas when oxygen in the loop volume is depleted and a diaphragm regulator re-injects to bring loop volume back up, or

• Active – Constant flow rate of Nitrox to loop-vent excess


INSPIRATION AND EVOLUTION• Closed Circuit rebreathers (CCR)

• State of the art electronic controls

• Onboard sources of air and oxygen, scrubber, computer controlled variable Nitrox mixing

• Everything the recreational and technical diver

needs


Section 3:

Mechanics and basic functioning

of the Inspiration and Evolution rebreather systems

Mechanics and basic functioning of the Inspiration and Evolution

• Diver’s Lungs• Mouthpiece and

Hoses• Exhalation

Counterlung• Manual Inject Buttons• Over Pressure

Release Valve• The Scrubber• The Scrubber

Cartridge• The Lid and handsets

• Three Independent Oxygen Sensors

• The Handsets and Gas Control

• Battery Compartment

• Warning Buzzer

• Cell Connectors

• The Oxygen Supply

• Inhalation Counterlung

• Diluent Gas Supply


• Including Optional System Components– Auto-Diluent Additional Valve (ADV) and inline

LP Flow Stop control device– Vision Electronics System (Factory Purchase)

• Includes a redundant LED head-up Display (HUD). Standard on the Evolution, the Vision package is optional on the Inspiration.

• Optional Scrubber monitoring temperature sensing

“Stick”


DIVERS LUNGS• The motor that powers the gas around the

rebreather gas loop

• The point of exchange for O2 rich gas to the body and CO2 rich gas from the body

• When we inhale, “clean” O2 rich gas comes in from the left.

• The flow is from the divers lungs through the mouthpiece to the right


MOUTHPIECE and HOSES• Mouthpiece and one-way mushroom valves

control direction of gas flow

• Timing of gas flow is in sympathy with diver’s breathing pattern.

• Hoses are large bore. This reduces the work of breathing (WOB)

• Mouthpiece hose is weighted for dynamic balance - adjustable


EXHALATION COUNTERLUNG• Counterlungs come from the factory in 4 different

sizes – User Selectable

• Contains first fixed T-piece and “water-trap” flow valve directing gas and water into the exhalation counterlung

• Flexible breathing bag to contain gas from body

• Contains both the Manual Oxygen Addition Valve and the Gas Loop Over Pressure Release Valve


THE CO2 SCRUBBER (or Stack)

• Gas path is from the exhalation counterlung, through the T-piece down to the bottom of the CO2 scrubber

• It fans out to a large bore axial flow through the scrubber to reduce gas velocity and increase “Dwell Time” for CO2 removal


THE SCRUBBER CARTRIDGE• Designed to remove CO2 from the gas loop.

• Spring loaded to maintain air gap at bottom

• Designed with Hydrophobic membranes for prevention of water absorption

• Contains upper and lower plastic retainers for the scrubber material


The Scrubber Cartridge – continued• Different scrubber makes can give different

duration times due to different granule sizes

• Spacer and o-ring for prevention of gas by-pass up the side of the scrubber canister

• Only designed to remove CO2, not any other toxic compounds or contaminants in the breathing gas


SCRUBBER MATERIALS• Have a defined shelf life time and in use up to 3 hours

• Effectiveness altered by time, temperature and moisture

• Sofnolime 797 grade recommended ( Other makes include Dragersorb and Sodasorb)

• Sofnolime is primarily a Sodium Hydroxide compound

• Needs proper packing to prevent CO2 channeling

• Efficiency is reduced by high gas flow rates (fast or skip breathing) or focused “channeling” characteristics

• In a properly assembled and properly functioning CCR system the CO2 scrubber is the “Achilles Heel”


SCRUBBER MANAGEMENT• No partial filling of the scrubber. New full

canister every time

• Do not empty scrubber into a bag and re-pack the scrubber later- new and used granules are then mixed

• Do not store partly used scrubber for more than a few days. The material absorbs CO2 and grows mold


CONTROLLERS GENERAL• Power On

– No wet contacts– Switch on manually– Self testing electronics. Hear/see alarms and

hear solenoid firing– 3 control buttons, but classic uses a separate

power switch also


HANDSET CONTROLLER GENERALITIES• Handset controllers are electronic – handle carefully

• There are two independent handset “controllers” on all Inspirations/Evolutions

• The primary function of the controller is to control oxygen injection and display real time information to the diver

• The controller also drives the alarm systems and interfaces with the diver via 3 control buttons

• Can be switched on and off separately

• They are redundant in a Master/Slave combination

• Either controller can be the Master

CONTROLLER LOCATIONS• On the Inspiration Classic the controllers are in

the handsets

• On Vision Electronics the single handset is a display and keypad only – the controllers are in the Scrubber Lid


THE SCRUBBER LID and HANDSETS• The electronic “brains” of the device

• Function is to control the PPO2 of the breathing gas to a user defined setpoint and display this and other dive parameters to the diver visually (handset display) (and HUD on Vision) and audibly (buzzer alarms)

• Great care should be taken when handling them

• For transport fully assemble rebreather or carry lid and handsets separately in a padded bag

• Treat it with the same care as a laptop


3 INDEPENDENT OXYGEN SENSORS• 3 galvanic fuel cells each with a milli-volt output

proportional to the oxygen exposure across their outer faces (breathing gas)

• Voting logic of the computer for oxygen control purposes averages the nearest 2 readings and ignores the 3rd

• This information is displayed to the diver as PPO2 values

• Delicate pin connections

• Should never smell of “toxic” or other vapors



THE HANDSETS ( and HUD on Vision)• Redundant controller PPO2 readings displayed to the diver

• Inspiration has 2 handsets, Evolution has 1 handset

• Provide for underwater dive menu changes to suit environment

• Must be switched on to have a chance to drive the oxygen solenoid

• Will give indications of battery health, controller health, and cell health in real time, underwater

• Can drive audible and visual alarms

• Redundancy so that 1 controller can fail while the other allows you to safely exit the water

• Need to constantly be checking PPO2 on the handset

THE HANDSETS (and HUD on VISION) – continued

• Can drive audible and visual alarms

• Redundancy so that 1 controller can fail while the other allows you to safely control the rebreather and exit the water

• Need to constantly be checking the PPO2 on the handset during the dive


• CONSTANT PPO2 GAS CONTROL

• Remember Dalton’s Law from Advanced Nitrox Pressure gas = FO2 x Pressure

• At different depths (gas pressures) for a constant PPO2 controller setting we will have a Nitrox mix that changes proportionally to pressure

• At any given depth we can calculate the Nitrox mix for any given PPO2 setting



BATTERY COMPARTMENT• Two slots for the two 2CR-P2 lithium 6 volt batteries

• Battery life typically 15 – 20 hours for the master

• Slave battery life longer – not firing the solenoid


WARNING BUZZER (and HUD)• Connected to the scrubber lid but normally fed to the T-

piece by diver’s left ear (HUD goes same way to left side of mouthpiece)

• This is a secondary warning device, the handsets are the primary indicators always

• In conditions of low battery power alarms may fail before handsets do

• (The HUD provides green/red visual health status to the divers direct area of vision)


CELL CONNECTORS• These are delicate and covered with red or blue

moisture caps with holes for pressure equalization

• Take great care not to damage wires or connectors if changing cells


THE OXYGEN SUPPLY• Dive tank switched on

• HP to SPG on front of exhalation lung gives O2 pressure

• LP hose feeds O2 to the LID for the solenoid from the first stage regulator

• First stage regulator I/P must be 7.5 Bar

• Evolution uses 2 liter cylinders, Inspiration uses 3 liter cylinders

• Remember:- Rich mix Right, Lean mix Left



INHALATION COUNTERLUNG• O2 rich gas from the scrubber lid comes up to the

inhalation counterlung

• Blue color coded for hoses containing clean oxygenated gas with the CO2 removed

• Passes through the inhalation T-piece without “Water-Traps on the newer machines

• Blue Manual Diluent addition button at bottom of inhalation counterlung

DILUENT GAS SUPPLY• Need to use diluent below 6msw (20fsw)

• Manually add diluent on descent depressing the blue manual addition button on the inhalation counterlung “to equalize” the loop volume with pressure changes

• LP feeds both the wing BCD and the Auto-air OC bailout device

• Tank pressure is displayed on the SPG via HP hose over left shoulder

• Do not use for Drysuit inflation – use off board gas

• IP normally set to 9.5 Bar


OPTIONAL AUTO-ADDITION DILUENT VALVE –ADV and FLOW STOP CONTROL DEVICE

• Replaces Inhalation T-piece and does not contain a water-trap device

• Automatically allows diluent into the breathing loop from the diluent side via a diaphragm if loop pressure drops below ambient

• Flow Stop Control Switch on the LP hose from the diluent first stage feeding the ADV can be used to switch ADV off if free flowing or faulty


BOUYANCY WING and AUTO AIR• All Inspiration and Evolution CCR come fitted with

a wing and Auto-air as standard

• The bouyancy wing and Auto-air are fed by LP feed from the diluent first stage

• The Auto-air is an OC 2nd stage regulator connected directly to the diluent gas supply via the first stage regulator

• The wing can be fitted with an optional “crack-bottle” for alternate gas source inflation


Section 4: Classic Electronics Control


Classic Electronics Control

DUAL HANDSET CONTROLLERS• Liquid Crystal display on each with protective

clear faceplate • 3 white magnetic Hall-Effect control Switches –

spring loaded

• One black rotary power switch

• Power switch up = on

• Power switch down = Off

CLASSIC HANDSETS• Separate Power On/Off switch – beware it can

get caught in your gear and get switched off

• Each handset shows if it is Master or Slave

• Each handset displays the three cell readings in PPO2


• Each handset displays the current setpoint setting at the top of the screen

• Alarms are shown in text on the screen

• There is a start-up menu that scrolls through basic pre-dive conditions to check diluent, and asks if you would like to calibrate and check the oxygen valve

• The dive menu in water allows setpoint changes and changes to backlighting intensity

• Your Instructor will guide you through the cycle



Section 5: Vision Electronics Control

Vision Electronics Control

VISION• General

– Owners personal data is shown on screen– Software Revision Version shown on screen– Optional software versions are available for

Nitrox and Trimix diving– Vision Electronics available in German, Dutch,

Italian, Spanish, Portugese, French and English– Functionality and displays similar in many

respects to the classic Inspiration Handsets


SINGLE HANDSET SYSTEM• Liquid Crystal display mounted in aluminum case

• 3 black buttons for commands

• Twin redundant controllers C1 and C2 housed in Scrubber Lid

• Power on by left switch

• Power off by menu command by depressing right 2 buttons simultaneously

• Can select to power off C1 or C2(anytime) or All Off but not underwater


SINGLE HUD DEVICE• Dual redundant displays of twin LED’s one green one

red connected to C1 and C2

• Fiber optic cable running along mouthpiece hose connects to controllers in Scrubber Lid

• Green LED’s are “Good”

• Red LED’s are ‘Rong’ or Alarms

• HUD lighting intensity is user selectable

• Read handset to get the detail of type of alarm

• Visual alarms generated with audible alarms


OPTIONAL SCRUBBER TEMP STICK• Connects to Scrubber Lid via connectorised cable

and status is displayed on the handset

• It is NOT a CO2 monitor

• Temp Stick is a temperature sensing system to detect where the main ‘Burn Face’ of CO2 absorption is taking place through the scrubber segments

• It aids in scrubber maintenance monitoring


LCD HANDSET DISPLAY• Switches automatically from Surface Mode to

Dive Mode at 1.2MSW ( 4FSW) and back again at 0.9MSW (3FSW)

• The 3 PPO2 readings for the 3 cells are displayed across the middle of the LCD


• Power on– Will auto-check controllers, batteries, cells,

alarms and HUD. The temp stick, if fitted and connected, will also be checked

– Your instructor will guide you through the menus, but read the User Instruction Manuals first

– Status of Vision system components are displayed on the LCD as shaded or clear elements


SUB MENU SELECTION• Either CCR or DECO

• Deco theory and handset options and control is covered fully in MOD 2 Course and is only touched on in this program

• This Course addresses the Non-Decompression diving fundamentals of the CCR

• Includes High and Low setpoint selection and changes and optional handset adjustments.


Calibration– Start-up asks if you want to calibrate– Can go direct to DIVE MODE for ‘Dry Dive’– Usually calibrate before each dive– Calibration procedure for cell mV output calibration

– Prompts on screen to check O2 valve, diluent valve, and system bailout


AUTO SETPOINT SWITCHING• User selectable manual or automatically upon

reaching a pre-determined depth

• Latest S/W version allows different depths for

auto-switching on descent and ascent


BUTTON CONTROLS• Center button is to select option on screen

• Outside two buttons to scroll up and down the menu screens

• Left button powers on the Controllers

• Right two to enter power down sequence


Section 6: Physiology – A Reflection for the CCR Diver

Physiology – A Reflection for the CCR Diver

BASIC PREMISE• We need to breathe clean (CO2 and toxic gas free),

appropriately oxygenated gas at all depths at all times to sustain life and to minimise DCS risk

• Appropriate nitrox mixes are delivered to the diver under software control according to the PPO2 selected by the diver

ADDITIONAL CONCEPTS• The low and high PPO2 default setpoints of the

Inspiration and Evolution are set at 0.7 and 1.3 respectively

• Ascent must be controlled at less than 9m per minute as per normal diving practice. DSC and DCI risks still apply

• Dangers of hypoxia, hyperoxia, asphyxia and the insidious CCR carbon dioxide poisoning (hypercapnia) need examination

• Lets review sources of contamination of breathing loop• NOAA toxicity guidelines apply for Whole Body and

Pulmonary Toxicity


CO2 and HYPERCAPNIA• Humans consume O2 at a cellular level and

generate CO2 as a waste product

• Blood transports O2 to the cells and removes CO2

• Blood exchanges CO2 for O2 at the lung Alveoli

• The urge to breathe is driven by the level of CO2 retained in the body (blood and cells)

• With hypercapnia and elevated CO2 levels, the breathing rate is increased (panting – dypsnea) to try to vent the lungs and alveoli


HYPERCANPNIA SYMPTOMS• Mild Symptoms

– Headache– Anxiety and dizziness– Shortness of breath

• Severe Symptoms– Strong anxiety bordering on panic– Muscular difficulty and loss of dexterity in closing

mouthpiece to bail out to OC– Diluent flush doesn’t seem to have any effect at first so

divers often stop flushing when in fact they should continue flushing non-stop


RE-INHALATION OF CO2

• CO2 normally removed by Sofnolime scrubber

• Conditions when this doesn’t occur properly– Scrubber expired or ignoring 3 hour duration rule– Strenuous activity on rebreather– Incorrect assembly of rebreather – missing O-ring– Wet or flooded scrubber– Damaged mushroom valves – gas goes backwards– Skip breathing or breath holding – creates pockets of

very high CO2 content in the breathing loop– Incorrect scrubber packing


DEPTH VERSUS CO2• As depth increases, work of breathing increases to

push more gas molecules around the breathing loop. More CO2 is generated as a result.

• As gas density of molecules increases the efficacy of the scrubber granules to absorb CO2 across its surface decreases


HYPEROXIA• Too much oxygen results in O2 toxicity risk

• Inspiration/Evolution alarm is set at a PPO2 of 1.6 or above

• Track O2 toxicity per NOAA tables (see manual)

• At a default setpoint of 1.3, NOAA limit = 180 minutes - But 80% of that is 144 minutes

• Do not exceed 80% of CNS and OTU tables

• Need to monitor CNS% and OTU’s carefully on multi-dive days or multiple repeat dive days


SYMPTOMS OF HYPEROXIA• CONVENTID

– CON Convulsions– V Visual disturbances/Tunnel vision– E Ears ringing (Tinnitus)– N Nausea– T Tingling or twitching (facial)– I Irritability– D Dizziness or vertigo


PULMONARY TOXICITY• O2 causes the alveoli surfaces in the lung to dry

out thus slowly reducing lung efficiency

• OTUs – 1 minute of 100% oxygen breathing at the surface

• Happens above a PPO2 of 0.5 thus very real danger for CCR and Inspiration/Evolution diving


HYPOXIA• Occurs if the PPO2 drops below 0.16 at any time

• Real danger on ascent if solenoid fails

• Real danger if Oxygen tank is off or empty

• Symptoms can typically be breathlessness and panting, and lack of co-ordination

• Unconsciousness resulting in drowning can be sudden and without warning


CNS TOXICITY AND OTU’s• Real danger of convulsing and drowning if your

CNS is not monitored properly

• Always know the PPO2 in the loop and do a diluent flush to check any odd readings

• Track your CNS % and OTU’s on the NOAA tables in your manuals


ASPHYXIA• Like strangulation it is caused by a shortage of

oxygen and buildup of CO2

• Restrictions in the breathing loop like a kinked mouthpiece hose can cause it

• Easily noticed early in a dive

• Ineffective or exhausted scrubber also can cause asphyxia

• Eventually results in unconsciousness



Section 7:

Let’s Go Dive the Rebreather - Preparation

Let’s Go Diving the Rebreather - Preparation

EQUIPMENT ASSEMBLY and INSPECTION• Preparation

– Assemble the rebreather according to a checklist (refer to manual), initially under Instructor guidance

– Be meticulous and do not get distracted

Pay particular attention to the following during assembly and inspection;

• Positive & negative pressure tests

• Cylinder contents analysis

• Cylinder pressure on SPGs

• HUD LEDs functioning (if HUD used)

• Alarm working audibly

• Listen for solenoid firing and alarm sounding when handsets switched on

• Switches on handsets working normally

• Mushroom valve checks on the mouthpiece assembly


• Wing and Auto-Air checks

• Scrubber packing, O-ring and spacer functioning

• Hose O-ring lubrication

• Battery power levels

WEIGHTING AND TRIM• Ensure the unit is well weighted at the top.

• Add to the sides on the waistband to trim

• More weight needed if diving in a drysuit


MACHINE CALIBRATION• Absolutely critical part of the preparation process• Always put in % of oxygen in the lid at 98% - all

the air cannot be displaced from the lid• Ensure the millibar pressure is correctly entered• Is the Mbar reading on the Vision handset

correct? (Automatically sensed)• Mbar readings are critical for altitude diving• Watch the cell readings rise during calibration

and check for any “slow” or “limited” cells


Calibration of O2 cells O/P– Your instructor will demonstrate

– Watch for rate of change of cell readings as oxygen is injected to Scrubber Lid

– Only calibrate with the unit upright, vertical and dry inside


• Calibration– Start-up asks if you want to calibrate– Can go direct to DIVE MODE– Usually calibrate before each dive– Calibration procedure for cell mV output

calibration

– Prompts on screen to check O2 value, diluent value bailout


BATTERY POWER MANAGEMENT• 2 x Lithium CRP2 batteries• One per handset/controller• Either change both batteries together, or cycle• New battery goes to slave, slave goes to master

and old master is discarded• Backlighting consumes power• Solenoid firing consumes power• Alarms consume power


GETTING THE FEEL OF THE MACHINE ON LAND• Putting on the machine for a “dry dive”

– Adjust straps to fit body correctly and tuck away loose ends

– Power up and sequence handset control through to dive mode under guidance of Instructor

– Go to a low setpoint of 0.5 – Put on mask to prevent breathing through nose– Breathe on the machine while watching PPO2

readings on handsets listen for solenoid firing


• Dry dive simulations (approx 30 minutes)• These provide useful simulations in a safe

environment for learning and troubleshooting


OVERFILLED BREATHING LOOP• Allow loop volume to increase by injecting a

little diluent.

• Get the feel of “over pressurized loop” inhibiting the exhale cycle

• Release excess gas – repeat again


UNDERFILLED BREATHING LOOP• Exhale fully through the nose, twice

• Feel the effect of too little pressure in the loop, difficulty inhaling properly

• Add gas using diluent button or, if there is an ADV, turn it on for volume adjustment


NORMAL LOOP VOLUME• Continue normal breathing mode while seated or

stationary

• Observe PPO2 readings and how closely they follow the setpoint

• Listen to solenoid firing and ensure you are feeling fine on machine


GENTLE EXERCISE• Walk about with the rebreather on

• Simulate moderate exercise

• Notice breathing, rate increases, and solenoid firing more often than when at rest.


INCREASED WORK LEVEL• Jog in place for a couple of minutes, or do a few

squats with the machine on to raise heart and respiratory rates

• Observe PPO2 tracking, hear solenoid firing and notice little or no change in loop volume

• The student should still feel fine and have no CO2 problems


LOW ALARM CHECK• Sit, relax and come off the machine – breathe

normal air

• Blow air into the loop to drop the PPO2 below 0.4

• Check for alarms and observe PPO2 coming back to setpoint again under automatic computer control


REDUNDANT CONTROLLER CHECK• Strictly under Instructor supervision

• Repeat Low Alarm Check with handset or controller C1 switched off

• Ensure redundant controller works, initiates alarms and brings PPO2 back to setpoint

• Switch handset or controller C1 back on again


SETPOINT CHANGES• Switch to High and then back to the Low

Setpoint when the PPO2 rises to 0.9 and observe PPO2 on handset

• Test how long it takes to breathe the loop back down to a PPO2 of 0.5 at rest


OPEN CIRCUIT BAIL-OUT• Close mouthpiece and come off the loop

• Switch to OC bailout – Auto-Air, take 3 breaths, return to the loop and open mouthpiece

• Observe loop volume increase as O2 is injected to bring PPO2 back up to setpoint because of the air you introduce to the loop

• Alarm for Low PPO2 may also sound when returning to loop and filling it with air


DILUENT FLUSH• Inject diluent using manual addition button on

inhalation counterlung while breathing in

• Vent gas through over-pressure release valve while exhaling

• Repeat three times and observe reduction in PPO2. Listen to solenoid firing. It is possible that the PPO2 may drop below 0.4 and cause an alarm


MANUAL GAS ADDITION• Give a small squirt of O2 with the manual addition

button and observe the PPO2 reading

• Repeat the exercise with diluent

• Repeat to get a “feel” for the addition buttons



Section 8: Let’s Go Dive the Rebreather – In the Water

Let’s Go Diving the Rebreather – In the Water

Rule No 1 • If in doubt – bail out!

Rule no 2• If something feels wrong – it is!

DIVE PLANNING• Select depth and time for a safe no-deco time

• Scrubber monitoring and planning (2.5 – 3 hour rule)

• Gas volume planning – enough for a bail-out

• Oxygen planning – CNS% and OTUs

• Is this a repetitive dive?

• Thermal protection appropriate for conditions and duration of dive

• Brief team, do ABCs and enter the water under guidance of your Instructor


FIRST IMPRESSIONS IN THE WATER• Silence

• Bubble-free

• Listen for the solenoid firing

• Check PPO2 on the handsets every minute

• Dynamic bouyancy change caused by computer-controlled oxygen

• Unit is bouyant at shoulder level due to air volume in counterlungs and hoses

• Add weight at the top for trim

• Remember – no matter how experienced you are on OC, you are now a beginner again


EARLY TECHNIQUE POINTERS• Do not expect to get it right first time

• Try to keep the loop volume at a minimum for comfort

• Keep a steady depth level

• Try to maintain a horizontal, neutral bouyancy, attitude while swimming

• Use vertical attitude only when testing skills under instructor guidance

• Be generous with weighting (1 or 2kg over)


BASIC WATER SKILLS DEVELOPMENT• Mouthpiece opening and closing techniques

• Open Circuit bail-out to Auto-Air

• Diluent flushes and checking PPO2 drop

• Check diluent flush predictions

• Bouyancy normalisation while swimming

• Constant checking of PPO2 on handsets

• Understanding and reacting to alarm conditions (mostly simulated while on course)

• Loop volume control


BAD – DAS DRILLS• In the event of in-water problems, rely on

BAD-DAS drills– B Bail-out to open circuit– A Anxiety breaths (3)– D Decide what to do

• If returning to the loop, then:– D Diluent flush – breathe fresh gas– A Always know your PPO2 – check handsets– S Skills. Apply appropriate skills gained

during training to overcome the problem


LOW O2 DRILLS• Manual flight

– 1 Using O2 inflator– 2 Adding oxygen using O2 tank valve– 3 Using machine in semi-closed circuit mode

• Low oxygen danger– 1 Solenoid stuck closed– 2 O2 tank empty or switched off

• Handset failure or switched off– If both are blank, go open circuit or if gas volumes

dictate, switch to semi-closed circuit mode


HIGH OXYGEN DRILLS• Open circuit bailout

• Use of diluent flush to drop PPO2

• Closing oxygen tank if solenoid fails open


MENU MODE DRILLS• Sequencing through menu commands in water

to become familiar with functionality

• Changing Setpoints

• Changing from one controller to the other

• NEVER CALIBRATE UNDER WATER


HYPERCAPNIA DRILLS• Open Circuit Bailout

• Diluent flushes

• Practice/Practice/Practice


ELECTRONICS MALFUNCTIONS• Handset and controller problems

• Cell errors or missing cells

• Intermittent alarms

• Poor PPO2 tracking to setpoint

• Possible Loop Floods



Section 9: Avoiding Rebreather Incidents – Safe Diving

Avoiding Rebreather incidents – Safe Diving

All the training in the world is useless if you do not adopt the following as your personal mantra for CCR Diving:

– Safe Attitude

– Safe and enhanced Awareness

– Safe and structured Discipline


OPERATIONAL MAINTENANCE• Check battery connections are clean and dry

• Ensure handsets are cleaned in fresh water, particularly Classic handsets with spring-loaded Hall-Effect slide switches

• Keep O-rings well cleaned and lubricated to prevent abrasion and other damage


• Properly assemble and check according to a check list

• Do not get distracted during calibration

• Do all the pre-dive checks and then “go live” for a short “dry-dive” to pre-breathe prior to entering water in order to ensure dynamic functionality of the machine

REMEMBER DURING PRE-DIVE PREPARATION


DIVE PLANNING• Break dive into logical “waypoints” to do

checks and flushes for safety

• Usual waypoints _ 6msw (20fsw) bubble leak check– On descent - switch to high setpoints– On reaching bottom - diluent flush and

check guages and handsets– After pre-set time or leaving bottom -

diluent flush– On ascent (10msw or less) - gas venting to

control bouyancy


REMEMBER ON THE DESCENT• Do a shallow (6msw/20fsw) bubble check

• Descend slowly to control breathing loop volume

• Watch the PPO2

• Switch to high setpoint according to plan


REMEMBER ON THE ASCENT• PPO2 will drop, solenoid should fire, and oxygen

should come into the loop quickly – rapid bouyancy increase

• Check PPO2 closely on ascent to reduce Hypoxic risk if there is insufficient O2 in the loop

• Carefully control ascent rate

• 3 potential bouyancy devices – drysuit, wing and loop counterlungs


REMEMBER AT THE SURFACE• NEVER switch off the handsets or tanks at the

surface above deep water

• Only shut down after equipment has been taken off

• You still need to watch your PPO2 if you breathe on the loop at the surface

• It’s the best snorkel you ever bought!!!


REMEMBER AFTER THE DIVE• Gas up again for the following dive

• Check and replace batteries/scrubber as necessary

• Disinfect and clean as necessary

• Conduct all other system checks to ensure correct functionality of cells and handsets

• Log your dives


TDI Training and Manufacturers Manuals– Errors and troubleshooting are well documented

for reference

– Maintain your own service log for batteries/scrubber and other service needs

– There is an “elapsed On Time” log kept on the controller until reset under menu control

– Document your rebreather experiences

Documents

TDI Evolution Closed Circuit Rebreather Diver Course by BorneoDream.com Billy Hammond #10407 - 2007