Dive Rite O2PTIMA CM User manual

October 2020 – Rev C
USER MANUAL

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October 2020 © Lamartek, Inc. dba Dive Rite 2
This is the user manual for the Dive Rite O2ptima CM eCCR rebreather.
This user manual is proprietary and copyright Lamartek, Inc. 2020. It may not be reproduced, changed,
or distributed without authorization from Lamartek, Inc.
All information contained in this manual has been carefully reviewed and is believed to be accurate,
however it is subject to change. Rebreather technology is constantly and rapidly evolving. Please check
www.diverite.com to ensure that you have the latest version of this manual.
Companies and/or product names cited in the manual are trademarks belonging to their respective
companies.
The O2ptima CM is manufactured in the USA by:
Lamartek, inc. dba Dive Rite
175 NW Washington Street
Lake City, FL, 32055 USA
Phone [phone]
www.diverite.com

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General Safety Statements and Warnings
 DO NOT use the O2ptima CM without successfully completing an O2ptima
CM specific training program. Training on previous versions of the back-
mounted O2ptima is not sufficient for diving the O2ptima CM.
 DO NOT use the O2ptima CM without reading and understanding this
manual in its entirety.
 Reading this user manual DOES NOT replace unit specific training. This
manual does not provide directions for diving with closed circuit rebreather
equipment. This manual is only intended to be a guide for the proper
maintenance, setup, operation, and basic service of the O2ptima CM
rebreather.
 As with any piece of equipment, this rebreather will eventually fail. Even
careful maintenance, assembly, and testing will not prevent this from
happening. It is possible that any part of this unit may fail at any time.
Because of this, it is essential that a separate, independent bailout system
be taken by the diver on every dive. The bailout system must be configured
to allow safe termination of the dive and return to the surface in the event
of a malfunction at any point during the dive.
 All components of the rebreather must be in good working order and be
carefully maintained, assembled, and tested to reduce the risk of failure.
 Participation in rebreather diving can result in serious injury or death.
These risks can be reduced, but never eliminated.
 Knowledge and training are the best tools for avoiding accidents.
 Rebreather diving is a physically as well as mentally demanding activity.
 If you do not have adequate training, equipment, physical conditioning, and
proper mind-set, do not get in the water.
 As the diver, YOU have the final responsibility for your own actions and
safety while using this rebreather.

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Table of Contents
General Safety Statements and Warnings .................................................................................................. 3
Introduction .................................................................................................................................................. 6
Design Philosophy ........................................................................................................................................ 6
System Overview .......................................................................................................................................... 7
The Breathing Loop ...................................................................................................................................... 8
Component Features & Functions ............................................................................................................... 9
Counterlungs .................................................................................................................................... 9
Breathing Hoses & Fittings ............................................................................................................... 9
Dive/Surface Valve (DSV) ................................................................................................................. 9
Automatic Diluent Addition Valve (ADV)/Manual Addition Valve (MAV) ..................................... 10
Oxygen Manual Addition Valve (MAV) .......................................................................................... 10
Overpressure/Dump Valve (OPV) .................................................................................................. 10
Scrubber Canister ........................................................................................................................... 11
Scrubber End Cap & Water Trap .................................................................................................... 11
Electronics Head ............................................................................................................................ 12
Oxygen Sensors .............................................................................................................................. 12
Controller ....................................................................................................................................... 13
Electronics/Battery Canisters......................................................................................................... 13
HUD ................................................................................................................................................ 14
Regulator, Hoses, & Gauge ............................................................................................................ 14
Cylinders & Valve ........................................................................................................................... 15
Micropore ExtendAir Cartridge Overview ................................................................................................. 16
Assembling the O2ptima CM ..................................................................................................................... 18
Importance of Checklists................................................................................................................ 18
Gas Analyzation .............................................................................................................................. 18
Installing the Water Trap Tubes ..................................................................................................... 18
How to Install a Micropore ExtendAir Cartridge ............................................................................ 19
How to Pack the Scrubber ............................................................................................................. 20
Installing the Scrubber End Cap & Water Trap .............................................................................. 23

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Installing the Electronics Head ....................................................................................................... 24
Installing the Scrubber Assembly ................................................................................................... 26
Mounting the Electronics/Battery Canisters ................................................................................. 27
Installing the Loop Hoses ............................................................................................................... 27
Installing the DSV ........................................................................................................................... 28
Installing the Oxygen Cylinder, Regulator and Hoses .................................................................... 29
Basic Operation & Use ............................................................................................................................... 32
Harness Attachment ...................................................................................................................... 32
Oxygen Sensor Calibration ............................................................................................................. 32
DSV Operation ............................................................................................................................... 33
Breathing on the Loop ................................................................................................................... 33
Electronic vs Manual Operation .................................................................................................... 34
Diluent Injection............................................................................................................................. 35
Servicing, Maintenance, & Cleaning .......................................................................................................... 35
Post Dive Procedures & Cleaning ................................................................................................... 35
Oxygen Sensor Care ....................................................................................................................... 36
Oxygen Sensor Replacement ......................................................................................................... 38
Battery Replacement ..................................................................................................................... 40
Battery Recommendations ............................................................................................................ 41
Storage ........................................................................................................................................... 41
Annual Service ............................................................................................................................... 42
Recommended Care Products ....................................................................................................... 42
Technical Specifications ............................................................................................................................. 42
Revisions & Changes in Documentation .................................................................................................... 44
Appendix I: Checklists ............................................................................................................................... 44
Assembly Guide Checklist .............................................................................................................. 45
Survival Checklist ........................................................................................................................... 46
Pre-flight Checklist ......................................................................................................................... 47
Post Dive Checklist ......................................................................................................................... 48
Appendix II: Galvanic Oxygen Sensors Applied to Closed Circuit Rebreathers ...................................... 49

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Introduction
Congratulations on your purchase of the O2ptima CM rebreather! First produced in late 2005, the
O2ptima has been a leader in the rebreather market for over a decade. During that time it has been
used for cutting edge exploration and world class expeditions all over the planet. Dive Rite has made a
strong commitment to ensuring that it is one of the most reliable, capable, and high performing
rebreathers on the market. The O2ptima design continues to evolve as refinements are made and new
technology becomes available. The O2ptima CM represents the next generation of O2ptima design. The
chest mounted configuration provides the advanced diver with new and unique opportunities for diving
exploration. We are certain that this unit will provide you with many unforgettable hours exploring your
underwater world.
Design Philosophy
The design parameters for the O2ptima were simple:
 Keep the breathing loop as short as possible
 Use proven, state of the art electronics
 Be fully compatible with the Micropore ExtendAir cartridge
 Maintain a rugged and durable package in the smallest profile possible
These parameters were originally chosen in order to produce a rebreather ideally suited to underwater
cave exploration. The unique challenges of the cave environment demanded a unit that was as safe and
reliable as possible while maintaining a minimal profile. The end result was a rebreather that is not only
highly suitable for cave diving, but also any other type of technical diving where a direct ascent to the
surface is not always possible.
By utilizing a horizontally mounted scrubber canister, the breathing loop was kept as short as possible.
This helps to create the lowest possible work of breathing and allows the use of smaller diameter loop
hoses. This in turn increases comfort and reduces diver fatigue. Internal water traps located in the
counterlungs and canister end cap, combined with the use of the Micropore ExtendAir cartridge, greatly
reduce the possibility of a “caustic cocktail.”
The O2ptima CM utilizes Shearwater electronics for their proven and unparalleled reliability and
functionality.
At Dive Rite, we understand that one size does not fit all, so in addition to the standard O2ptima CM
features there are a number of options to ensure a proper fit for any diver and mission. Contact Dive
Rite or visit www.diverite.com for more details.

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System Overview
The O2ptima CM is a chest mounted electronically controlled, constant PPO2, fully closed circuit
rebreather (eCCR). It has built-in decompression calculation and mixed gas capabilities. The following
features come standard on the unit:
 Chest mounted counterlungs with 6 Liter total loop volume
 Redundant Shearwater DiveCAN electronics including heads-up display (HUD) and Petrel 2
controller (NERD controller optional)
 Dual use scrubber canister design that can be used with Micropore ExtendAir cartridges or
packed with loose CO2 absorbent
 Dive Rite DSV is standard
 Dual water traps in the counterlungs and scrubber lid
 Oxygen Regulator and hoses
 (4) AI or AST R22 Oxygen Sensors
 Sturdy outer cover utilizing abrasion resistant Rhinotek® fabric
 AL 13 oxygen cylinder with valve (optional)

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The Breathing Loop
The O2ptima CM incorporates a chest mounted, dual counterlung design. The breathing loop consists of
the DSV, breathing hoses and hose fittings, inhalation and exhalation counterlungs, scrubber canister,
canister end cap, and electronics head. Gas flows from the diver—to the right counterlung—through the
scrubber canister—to the left counterlung—back to the diver.

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Component Features and Functions
Counterlungs
The O2ptima CM uses two integrated, chest mounted
counterlungs. The counterlung position keeps them as
close to the diver’s lung centroid as possible providing
excellent breathing characteristics in a variety of diver
positions.
The counterlungs consist of an abrasion resistant outer
bag and removable welded polyurethane inner bladders.
The bladders are accessible through a zipper on the back
side of the outer bag.
The bottom side of the counterlungs attach directly to
the scrubber canister. The breathing loop hoses attach to the sides of the counterlungs using threaded
connections.
The exhalation counterlung has an overpressure/dump valve located at the bottom of the lung. An
internal water trap is located in the bottom of the exhalation counterlung to make de-watering the loop
easy.
Breathing Hoses & Fittings
The hose diameter and lengths have been specifically chosen to provide the best
balance of comfort and low work of breathing. The hose lengths are some of the
shortest in the industry. This not only keeps the work of breathing low, but also
reduces drag and uncomfortable vibrations occasionally encountered with
excessive hose lengths when scootering or swimming against strong flow.
The hoses have threaded fittings attached to the counterlung ends. Each fitting
utilizes a double O-ring seal to help ensure loop integrity. The hoses are 12
inches in length standard. Other sizes are available for improved fit on smaller
divers.
Dive/Surface Valve (DSV)
The DSV has been completely redesigned from the ground up
for exceptionally low work of breathing in the most compact
design possible. Two high performance mushroom valves are
used to ensure proper one way gas travel.
The lever on the front of the DSV is used to open the DSV for
diving and close the DSV on the surface or during a bailout
procedure to prevent water from entering the loop. The DSV
utilizes a friction seal between the outer body and the inner
barrel so there are no O-rings to wear out or replace on the barrel.

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The DSV uses a bayonet style quick lock system to attach the hoses. To remove, simply press in the
spring loaded white locking button and turn the connector ring 1/8 turn counterclockwise. The hose can
then be pulled free. This feature allows fast and easy inspection of the mushroom valves and cleaning
and maintenance.
Automatic Diluent Addition Valve (ADV) /
Manual Addition Valve (MAV)
The ADV/MAV is mounted to the side of the inhalation
counterlung. It utilizes a built in demand valve that is activated
by negative loop pressure against a diaphragm in the same
manner as a standard second stage regulator. It can also be
manually activated by pressing directly on the diaphragm.
The ADV’s position allows it to feed diluent gas directly to the
DSV. This provides a fast, hands-free method of receiving a
known breathable gas as well as supplying additional gas to increase loop volume.
The ADV/MAV comes with a standard LP inflator hose fitting to allow the use of any off-board diluent
gas supply. For dives exceeding 130ft/40m, Dive Rite recommends upgrading this fitting to a high flow
quick disconnect QC-6 fitting. Contact Dive Rite for details.
An inline shutoff is included to disable the ADV, however be aware that this also disables the MAV.
The shutoff should also be used if the diluent gas supply is disconnected underwater to prevent water
from entering the ADV/MAV.
The base of the ADV/MAV is screwed into a welded flange on the counterlung inner bladder.
Oxygen Manual Addition Valve (MAV)
The oxygen manual addition valve is a dry-suit style, side push valve.
It uses a standard LP inflator hose connector. The valve allows the
manual addition of oxygen and also permits the use of on-board as
well as off-board gas supplies.
The oxygen manual add valve is located on the exhalation (right)
counterlung. The valve is screwed into a welded flange on the
counterlung inner bladder.
Overpressure/Dump Valve (OPV)
The O2ptima CM uses a special loop overpressure valve (OPV) located on the exhalation (right)
counterlung. A specific spring is used to optimize the cracking pressure for rebreather counterlung use.
Do not replace with a standard drysuit exhaust valve as they can have a much higher cracking pressure
which can lead to lung overexpansion injuries.

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This valve will normally be operated in the open position (turned fully
counter-clockwise). Divers with a large tidal volume may find that they
need to close the OPV slightly in order to maintain proper loop volume.
The valve can also be manually opened by pressing on the valve. The
valve is screwed into a welded flange on the counterlung inner bladder.
During an ascent, the gas in the loop will expand, increasing buoyancy
and slightly increasing the breathing effort. Even though the maximum
volume in the O2ptima CM’s breathing loop is relatively small, it is
important to set the OPV properly so that buoyancy shifts will be kept to
a minimum without any diver action.
The OPV is also used for de-watering the loop. This procedure will be covered in your O2ptima CM class.
Scrubber Canister
The scrubber canister contains the scrubbing media that removes CO2 from
the breathing loop. The O2ptima CM uses an axial style scrubber canister
and can be used with either Micropore ExtendAir cartridges or loose
packable CO2 absorbent.
Assembly is slightly different depending on which scrubber media is used.
The wave spring and top plate with screen are not used when using an
Extendair cartridge. The finger nut is reversible. It is used in one direction
when packing loose CO2 absorbent and is flipped over when using
Extendair cartridges. See the How to Pack the Scrubber section for more
information on properly seting up the scrubber canister.
Scrubber End Cap & Water Trap
The scrubber end cap contains a snap-in water trap in the shape of a
cone. This shape prevents excess water from entering the scrubber
canister regardless of the diver’s position in the water.
The shape of the cone also assists in mixing the exhaled gas with
added oxygen into a homogenous blend. The result is even gas flow
through the scrubber canister and accurate readings by the oxygen
sensors.
The end cap has an O-ring and a flat seal that seals against the
scrubber canister and an additional O-ring that seals the water trap. These O-rings and seal require
cleaning and maintenance and should be replaced on an annual schedule at a minimum.
The end cap attaches to the scrubber body by aligning the marks on the cap and body, pressing the cap
into place, and the turning the cap clockwise until the mark is aligned with the “locked” position
marking.

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Electronics Head
The electronics head contains the solenoid, oxygen sensors (4), sensor
disk, sensor wiring harness, and oxygen injection premix tube. These
components are responsible for analyzing the oxygen content of the
breathing gas and injecting oxygen as needed.
The controller (Shearwater DiveCan system) interprets the readings
from the oxygen sensors and makes decisions on when to add oxygen
via the solenoid.
The injected oxygen travels through the premix tube to the exhalation
side of the scrubber canister where it is blended with the loop gas
before going through the scrubber material. This reduces O2 “spikes” by ensuring that the gas mixture is
homogenous before passing over the oxygen sensors.
Oxygen Sensors
The O2ptima CM uses four oxygen sensors. These sensors are threaded into
the sensor disk mounted inside the electronics head. Dive Rite uses both
Analytical Industries, Inc. and American Sensor Technologies, Inc. type R22D
sensors.
Oxygen sensors have a finite life. They are a consumable item and must be
replaced at regular intervals. They are typically replaced during the annual
service, but may need to be replaced prior to this.
The sensor labeling includes a “Sell by” date of 4 months after manufacture
and a “Do not use after” date of 16 months after manufacture. Sensors must
not be used after this date even if they appear to still be functioning correctly.
Four sensors are used to provide redundancy and the ability to cross check their values against each
other to determine if a sensor is not reading correctly. Sensors 1 and 2 are shared between the
controller and the HUD. Sensor 3C is only connected to the controller, and sensor 3H is only connected
to the HUD. By comparing sensor readings between the HUD and the controller it is easy to determine if
a sensor is not reading correctly.
If sensor values 1, 2, and 3C do not agree, the controller automatically uses a voting logic to make an
educated guess of which sensor is not reading correctly. Having an independent “4th sensor” display on
the HUD allows the diver to independently verify the controller’s voting logic.
For more information on oxygen sensors, see the Oxygen Sensor Care section and also Appendix II:
Galvanic Oxygen Sensors Applied to Closed Circuit Rebreathers by Analytical Industries, Inc.

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Controller
Dive Rite has chosen to use Shearwater electronics to control and
monitor the O2ptima CM. The controller is a DiveCAN Petrel 2
handset. The controller allows diver control of the PPO2 setpoint
and PPO2 monitoring of oxygen sensors 1, 2, and 3C. It also
functions as a full featured dive computer displaying depth, dive
time, decompression information, and other important dive
information.
It is recommended to use a second standalone dive computer
with decompression information as a backup in addition to the
controller.
For detailed information on the DiveCAN Petrel controller, please see the Shearwater Petrel DiveCAN
Rebreather Controller Model Operations Manual.
Dive Rite now offers an optional Shearwater NERD controller for the O2ptima CM which allows full set-
point control without a Petrel 2 controller. Contact Dive Rite for more information.
Electronics/Battery Canisters
There are two external electronics & battery canisters on the O2ptima CM.
They are mounted between the scrubber canister and the counterlungs in
elastic sleeves on the bottom of the outer bag.
One canister contains the SOLO (SOLenoid and Oxygen) electronics board
and battery. The battery is a standard 9 volt battery that powers the SOLO
board as well as the oxygen solenoid. The Petrel 2 controller handset has
its own internal battery and does not rely on the 9 volt battery.
The other canister contains the OBOE (Oxygen BOard Electronics) board
and battery. The OBOE board controls the HUD. The battery is a standard
AA type. This battery only powers the OBOE board and HUD.
By locating the batteries in these external compartments, they are
completely isolated from the head and the breathing loop. This is
important because as batteries age or are damaged they can release toxic
chemicals. Obviously this is not something you want to have in your breathing gas.
The batteries are accessed via a threaded cap on the end of each canister. The caps are double O-ring
sealed to ensure water integrity. These O-rings must be inspected and maintained when the canisters
are opened to reduce the chance of flooding. See the Battery Replacement section for additional
information.
The electronics canisters connect to the controller and HUD using wet pluggable, waterproof
connectors. Regular lubrication of the inside of these connectors with a light coating of silicone grease
such as Molykote 111 will increase their usable life.

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HUD
The O2ptima CM includes a Shearwater HUD (Heads-Up
Display). The HUD displays the PPO2 readings of oxygen
sensors 1, 2, and 3H. These values are displayed using
three columns of LEDs. Each column represents a
different sensor. The colored LEDs flash using a modified
Smither’s code to convey the PPO2 values. A “color blind”
mode is also available. The HUD can be setup for right or
left eye operation. The HUD can be turned on manually by pressing the button on the end of the
housing. There are also wet contacts which automatically turn the unit on in case it was not turned on
prior to the dive.
Your life depends on always knowing the PPO2 in the breathing loop while diving a rebreather. Do not
make assumptions about how the HUD displays PPO2 values. Previous versions of the HUD used
different blink patterns. Refer to the latest Shearwater HUD User Manual for a detailed description of
the HUD blink pattern and operation.
The Shearwater NERD (Near Eye Remote Display) is also available as an option.
(https://www.shearwater.com/products/nerd/) The NERD replaces the standard HUD providing a
numerical readout of the 3 sensor PPO2 values and also serving as a backup computer with fully
redundant decompression and dive information. Dive Rite now offers a controller version of the NERD
which allows full set-point control without using a separate Petrel 2 controller. Contact Dive Rite for
more information.
Regulator, Hoses, & Gauge
A Dive Rite first stage with DIN connector and hose assembly is included
for the oxygen supply. First stage intermediate pressure (IP) is set to 85
psi for the oxygen regulator. The oxygen regulator IP must be set no
higher than 85psi due to the maximum rated pressure of the solenoid.
A diluent regulator and hoses are not supplied with the O2ptima CM.
The unit is only intended to be used with an off-board diluent supply
and it is up to the diver to supply these components as there are a wide
variety of possible configurations.
An over-pressurization valve (OPV) is installed in the oxygen first stage
for safety. Because there are no second stages installed there is no
other way for excess pressure to be released. The over-pressurization
valve must be in place in the event of a first stage high pressure seat
failure to prevent high pressure gas from reaching all of the downstream
components.
An OPV that is releasing pressure indicates a malfunction and the dive should be terminated
immediately. The OPV should be inspected for bubbling during the S-drill at the beginning of the dive.
The first stage needs to be serviced annually by an Authorized Dive Rite service center or directly by Dive
Rite. Call Dive Rite directly (1-800-495-1046) or email [email protected] to schedule service.

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Braided nylon Airflex LP hoses are used for oxygen gas supply on the O2ptima CM. Airflex hoses are
flexible, yet tough. The hose lengths are optimized for streamlined routing.
A small button SPG is included to monitor oxygen tank pressures. A BAR gauge is used to help simplify
gas consumption calculations.
An inline shutoff with safety lock is included. This should be closed any time the oxygen supply hose is
disconnected underwater to prevent water from entering the solenoid causing damage or failure to
operate. Once the oxygen supply hose is connected, turn the gas supply on and purge the line using the
oxygen MAV before opening the inline shutoff. Once the shutoff is open, install the included safety lock
clip to prevent accidental oxygen shutoff.
Cylinder & Valve
The base O2ptima CM does not include an oxygen cylinder, however they are
available. Dive Rite recommends an aluminum 13 cf (2L) cylinder for on-board
oxygen use. The diver may also choose to sling an oxygen bottle of their
choosing separately for off-board use.
The on-board cylinder is held in place with two included adjustable cam straps.
No additional cylinder mounting hardware is necessary.
The AL13 cylinder is a good compromise between weight and gas volume. It is
an excellent choice for general rebreather diving. Other recommended cylinders
that will work as on-board bottles with the O2ptima CM are:
 Aluminum 20 cf (3L)
 Steel AA LP13 cf (2L)
 Steel AA LP15 cf (2L)
 Steel AA LP27 cf (4L)
 Steel AA HP32 cf (4L)
However, the larger cylinders may have undesirable buoyancy characteristics when used as on board
cylinders. Divers should select cylinders based on their dive duration, travel logistics, and buoyancy
characteristics.

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Micropore ExtendAir Cartridge Overview
(Information from www.microporeinc.com)
ExtendAir® adsorbent technology is a combination of a microporous gas
adsorbent sheet and the geometry in which it is utilized. The adsorbent
material is manufactured with a proprietary process into a microporous
sheet that can be made into different thicknesses and widths, using the same
chemistry as in granular adsorbents.
Sheets of adsorbent material are wrapped around a core to form an
ExtendAir® cartridge. The molded ribs in the
material create channels through which the breathing gases flow. One of
the unique features of an ExtendAir® cartridge is that the breathing
resistance of the adsorbent can be precisely controlled by varying rib
height and spacing. This controlled channeling of the breathing gases
results in a very uniform reaction zone within the adsorbent.
In a granular canister, gases seek the path of least resistance through the bed. The flow pattern can be
very random and will certainly vary from person to person. Learning to load a granular canister requires
instruction to learn the proper technique. Optimal loading of the canister
requires tapping to achieve a uniform bed of granules. This takes time and
can cause dusting of the adsorbent. All of this leads to variations in duration,
wasted adsorbent and the potential for "caustic cocktail".
In contrast to a granular system, ExtendAir® cartridges use channels, molded
in at the factory, that remain constant and controlled by the manufacturing
process. The user simply places the
cartridge into the canister, without any
need for tapping or shaking as the canister
is being loaded. As such, the duration
variability due to irregular granule settling
patterns, as well as variability due to individual loading technique are
completely eliminated. Eliminating this variability will directly
translate into longer minimum duration, and a +/-5% variation in
duration at any test condition (granules can vary up to +/-30%).
An important concept to understand with ExtendAir® cartridge technology is that the gas flow
distribution through the cartridge must be uniform in order for the system to perform optimally. For
example, one way to visualize flow through an ExtendAir® cartridge system is to take a bunch of soda
straws in your hand (50 or so). What would happen if you blew air down through just a group of 5
straws? All of the air would flow down those five straws, and none of the air would flow through the
other 45. The same thing would happen if you blew air into just one side of an ExtendAir® cartridge
canister: all of the air would flow through that side only.

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The end result of this uniform flow is full utilization of the adsorbent in the cartridge.
To achieve full adsorbent utilization, Micropore designs canisters to achieve a +/- 5% flow distribution at
the inlet face of the ExtendAir® cartridge. This is accomplished through various engineering techniques
such as diffusion screens and flow testing of the breathing loop. The result is a system engineered to
perform consistently independent of individual loading
techniques.
The combination of Micropore’s ExtendAir® adsorbent
manufacturing process, along with the parallel flow cartridge
design, turns out to be extremely efficient. Installing an
ExtendAir® Cartridge (EAC) is relatively simple, and takes seconds
to perform. The O2 injection tube runs through the center of the
EAC and with the use of a plug any possibility of “CO2
Channeling” is prevented.

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Assembling the O2ptima CM
This section will explain basic assembly procedures of the O2ptima CM. These instructions will serve as a
guideline for correct initial assembly as well as disassembly necessary for transportation or
maintenance.
Importance of Checklists
Many rebreather accidents and fatalities could have been prevented with the use of assembly and pre-
dive checklists. There is nothing particularly difficult about assembling a rebreather, however there are
many small yet important steps in the process. A small oversight such as forgetting to re-install an O-ring
can have disastrous consequences.
We are all human and as such are susceptible to distraction and lapses in memory. There is
overwhelming evidence pointing to the efficacy of checklists in preventing errors in complex technical
procedures. It is highly recommended that you use a written or digital checklist for both assembly and
pre-dive checks before every dive. See the Checklists section in this manual for assembly and pre-dive
checklists.
Gas Analyzation
The most important rule of rebreather diving is to always know what gas is in the breathing loop. This
process begins with analyzing the contents of your cylinders.
Sensor calibration is performed assuming a certain percentage of oxygen, however the only way to
know what percentage of oxygen the cylinder actually contains is to analyze it. If the actual percentage
of oxygen in the cylinder is different than what is assumed, it could lead to an incorrect calibration
resulting in a different gas mix in the loop than what is displayed on the HUD and controller. This could
result in oxygen toxicity or errors in decompression calculations.
It is highly recommended that both oxygen and diluent cylinders, along with any bailout cylinders, be
analyzed and the contents labeled on the cylinder prior to assembling the unit. .
Installing the Water Trap Tubes
Begin by installing the water trap tubes into the counterlungs. Lay the outerbag with the back side facing
up. One end of each tube is slightly flared to prevent it from sliding too far into the fitting. Note that the
tubes are different and one is labeled “IN” for “Inhale” and one is labeled “EX” for “Exhale”. The Inhale
tube has holes toward the bottom to allow water to drain from the inhale loop back through the
scrubber. The Exhale tube has holes at the top to allow for water trapping while ensuring the
counterlung bladder cannot block off the end of the tube causing hard breathing.
Inserting the non-flared end first, slide the correct tube into each counterlung from the bottom fitting
until it is fully inserted (See Figure 1). Note that the exhale side tube will have more resistance when
inserting because there is an O-ring inside of the exhalation counterlung fitting but not the inhalation
side fitting. This is to trap any water inside the exhalation counterlung for de-watering through the OPV.
The O-ring is not needed on the inhalation side.

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How to Install a Micropore ExtendAir Cartridge
The next step in the build process is to assemble and install the CO2 scrubber canister. The O2pitma can
be used with either the Micropore ExtendAir cartridge or it can be packed with loose granular CO2
absorbent. This section will deal with using the ExtendAir cartridge. If you are using loose granular
absorbent, skip to the next section, How to Pack the Scrubber.
To use an ExtendAir cartridge, begin by inspecting all of the scrubber components. Look for any damage,
dirt, debris, or excess lubrication on the scrubber canister, ExtendAir cartridge, scrubber end cap,
electronics head, bore plug nut, and seals and O-rings. Any damage or contamination can cause a loss of
water integrity and flooding of the breathing loop.
Next, remove the ExtendAir cartridge from its packaging and, using a permanent marker, mark the
installation direction on the side and/or end of the cartridge. If the cartridge is removed between dives
and then later reinstalled, it is critical that the cartridge be reinstalled in the same orientation to prevent
premature CO2 breakthrough. Install the cartridge by sliding it all the way into the canister (See Figure
2).
Figure 1 – Inserting Water Trap Tubes—Inhale on Left, Exhale on Right
(note hole location)
Figure
2
-
Installing EAC
Figure
2
–
Installing ExtendAir Cartridge

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Next, install the bore plug nut with the tapered end toward the cartridge. This tapered end will seal
against the center bore of the cartridge. Tighten by hand until snug (See Figure 3). The included wave
spring and top plate with screen are not used when using an ExtendAir cartridge. The canister is now
ready to be installed on the unit.
How to Pack the Scrubber
The scrubber canister can be packed with approximately 5 pounds of loose granular CO2 absorbent.
Dive Rite recommends Intersorb 812 or Sofnolime 797 (8-12 mesh) granular absorbent. 408 (4-8 mesh)
is not recommended. It is important to use fresh absorbent for every dive. Granular absorbent should
never be reused.
To pack the scrubber, begin by inspecting all of the scrubber components. Look for any damage, dirt,
debris, or excess lubrication on the scrubber canister, scrubber end cap, electronics head, bore plug nut,
and seals and O-rings. Any damage or contamination can cause a loss of water integrity and flooding of
the breathing loop.
Dive Rite includes a filter disc that should be used when packing the scrubber with granular absorbent.
This is to reduce the amount of dust that reaches the head and the rest of the breathing loop. It is
placed in the bottom of the scrubber body, underneath the stainless steel mesh screen. This filter is
optional when using an ExtendAir cartridge. The filters are reusable but will need to be replaced
eventually. Replacements can be ordered from Dive Rite in packs of 3.
Ensure that the filter is in place and the stainless steel screen mesh is correctly seated on top of it in the
bottom of the scrubber canister (See Figure 4).
Figure
3
-
Bore Plug Installation for EAC
Figure 4 – Filter and Screen Installed in Scrubber Canister