Hollis Explorer User Manual

user Manual

REV. 2

This is the operations manual for the
HOLLIS EXPLORER

This manual, specifications and features of the Explorer are proprietary and
copyright Hollis Inc., 2012.

This document cannot be copied or distributed without the prior agreement and
authorization from Hollis Inc.

All information contained is subject to change. Contact the manufacturer for the
latest information. www.hollisgear.com

The EXPLORER is manufactured in the USA by Hollis Inc.,
2002 Davis Street, San Leandro, CA 94577. USA
Ph [phone]

EC Type approved by SGS UK Ltd. Weston-super-Mare. BS22 6WA. Notified
Body No. 0120.

Testing conducted by ANSTI Test Systems. Hants.

To ensure your user information is up to date. Please check
www.hollisgear.com/support.asp for updates to this manual.

For warranty information see www.hollisgear.com/support_warranty.asp

DANGERS, WARNINGS, CAUTIONS, AND NOTES
Pay attention to the following symbols when they appear throughout this docu­ment. They denote important information and tips.

!

DANGERS: are indicators of important information that if ignored would lead

to severe injury or death.

WARNINGS: are indicators of important information that if ignored could lead

!

to severe injury or death.

CAUTION

CAUTIONS: are indicators of information that if ignored may lead to minor to

moderate injury.

NOTES: indicate tips and advice that can inform of features, aid assembly, or

prevent damage to the product.

EXPLORER DESIGN TEAM

Bob Hollis
Kevin Gurr

HollisExplorer
User Manual

Document Control Number: 12-4102
Rev. 2
Publish Date: 7/26/2013

WARNING:

!

USE OF THE EXPLORER MANUAL

This user manual does not, nor is it intended to
contain any information needed to safely dive with
any type of SCUBA apparatus. It is designed as a
guide for the proper setup, operation, maintenance,
and field service of the Hollis Explorer only. It does
NOT take the place of a recognized training agency
instructor-led diver-training course or its associated
training manual(s) and materials. This user manual
is intended to be used only as a type specific ad­dition to such training and materials, and as a user
reference. This manual cannot be used as a sub­stitute guide for any other type of Self Contained
Underwater Breathing Apparatus (SCUBA).

Photo by:

www.HINDL.com

GENERAL SAFETY

STATEMENTS + WARNINGS

WARNING:

!

GENERAL SAFETY

No person should breathe from, or attempt to operate in any way, a Hollis Explorer rebreather, or any
component part thereof, without first completing an appropriate Hollis Certified user-training course.

Further, no Explorer diver should use a Hollis Explorer without direct Hollis instructor supervision until
they have mastered the proper set-up and operation of the Hollis Explorer rebreather. This includes
new Explorer divers as well as Explorer certified divers who have been away from diving for an extend­ed period of time and would benefit from an instructor-led refresher course to regain skills and mastery
of the Hollis Explorer. Failure to do so can lead to serious injury or death.

WARNING:

!

NITROX STATEMENT

The EXPLORER equipment is classified as being suitable for use with nitrogen-oxygen (Nitrox) breath­ing gas mixtures containing up to 40% oxygen by volume without the need for special preparation,
cleaning , or component parts.

If Explorer equipment is subsequently used with equipment, or connected to an air supply system, that
is not rated for Oxygen Service, it can subsequently be used with Nitrox (up to 40% O2) as long as the
equipment is maintained in accordance with the procedures and parts specified in the Hollis EXPLOR­ER Product Service Guide.

The EXPLORER was designed for use with Nitrox (up to 40% O2). DO NOT use gas mixtures with a
higher fraction of oxygen greater than 40% with your EXPLORER.

WARNING:
CAUSTIC MATERIAL

The CO2 absorbent used in the scrubber is caustic alkaline material. Take steps to protect yourself from

direct lung and skin contact. Furthermore, poor management of the breathing loop could lead to water

contact with the CO2 absorbent, causing a “caustic cocktail” (very caustic liquid). This could lead to se-

vere chemical burns and if inhaled - possible drowning. Proper handling procedures, pre-dive checks,

dive techniques, and maintenance mitigates this risk.

iv |

WARNING:

!

DESIGN AND TESTING

The Hollis Explorer has been designed and tested, both in materials and function to operate safely
and consistently under a wide range of diving environments. You must not alter, add, remove, or re­shape any functional item of the Hollis Explorer. Additionally, NEVER substitute any part of the Hollis
Explorer with third-party items which have not been tested and approved by Hollis for use with the
Explorer.

This includes, but is not limited to, hoses, breathing assemblies, electronics, breathing gas delivery
assemblies and their constituent parts, sealing rings, valves and their constituent parts and sealing
surfaces, latches, buoyancy devices, inflation and deflation mechanisms and on-board alternate
breathing devices.

Altering, adding, removing, re-shaping or substituting any part of the Hollis Explorer with non-ap­proved parts can adversely alter the breathing, gas delivery or CO2 absorption characteristics of the
Hollis Explorer and may create a very unpredictable and dangerous breathing device, possibly lead­ing to serious injury or death.

Non-approved alterations to functional parts of the Explorer will automatically void all factory war­ranties, and no repairs or service work will be performed by any Hollis service professional until the
altered Explorer unit is brought back into factory specifications by a Hollis service professional at the
owner’s expense.

WARNING:

!

COMPUTER / CONTROLLER-SPECIFIC WARNINGS

This computer is capable of calculating deco stop requirements. These calculations are predictions of
physiological decompression requirements. Calculations are for contingency use only. The Explorer
in this “sport” configuration is not intended for decompression use.

| v

TABLE OF CONTENTS

General Safety Statements & Warnings

PART 1

YOUR NEW EXPLORER

SECTION 1

REBREATHER LIFE SUPPORT SYSTEM
RULES

SECTION 2

BATTERIES

SECTION 3

UNIT LAYOUT

SECTION 4

COVER REMOVED

SECTION 5

GAS FLOW

SECTION 6

MECHANICAL FEATURES

PART 2

OUT OF THE BOX

SECTION 1

INITIAL ASSEMBLY

PART 3

LIFE SUPPORT SYSTEM
(COMPUTER)

SECTION 1

GENERAL OPS

SECTION 2

AUTOMATIC TURN ON

SECTION 3

DISPLAY SYMBOLS

SECTION 4

SCREEN ICONS

SECTION 5

DIVE SCREENS

SECTION 6

STATUS SCREENS

SECTION 7

MAIN MENU

SECTION 8

SETUP MENU

iii-v

SECTION 9

BAILOUT & GAS CONFIGURATION

SECTION 10

DCP (DIVE CONTROL PARAMETER)

SECTION 11

RMS(RESOURCES MANAGEMENT SYSTEM)

SECTION 12

O2 SENSOR CALIBRATION

SECTION 13

O2 SENSOR VOTING

SECTION 14

CDM (CANISTER DURATION METER)

SECTION 15

DISPLAY & ALARM SYSTEMS

SECTION 16

ALARM FLOW DIAGRAMS

SECTION 17

GAS RESERVES

SECTION 18

MOD (MAXIMUM OPERATING DEPTH)

SECTION 19

DECO CONTINGENCY

SECTION 20

INTERNET REPROGRAMMING

PART 4

GETTING READY TO DIVE

SECTION 1

GEAR PREP

SECTION 2

PRE-DIVE SETUP

SECTION 3

COMPLETING PRE-DIVE CHECKS

SECTION 4

USER FAULT FINDING & TESTING

PART 5

MANDATORY DIVING SKILLS

SECTION 1

EXPLORER BASICS

SECTION 2

IN-WATER SKILLS CHART

vi |

SECTION 3

EXPLORER SKILLS COMPLETED

PART 6

COMPLETE DISASSEMBLY &
REASSEMBLY

SECTION 1

THE FULL DEAL

PART 7

USER MAINTENANCE & AB­SORBENT STORAGE

SECTION 1

O2 SENSORS

SECTION 2

SANITIZING

SECTION 3

CO2 ABSORBENT

SECTION 4

SERVICE

SECTION 5

MAINTENANCE SCHEDULE

PART 8

APPROVED PRODUCTS &
GLOSSARY

SECTION 1

APPROVED PRODUCTS

SECTION 2

GLOSSARY

| vii

1.1

Your New Explorer

Rebreather LifE Support
System Rules

!

DANGER: Read and understand this list prior to using this unit.

Rules for EXPLORER Diving

1. Always complete all pre-dive checks. Pay special attention to BOV
mushroom valve tests.

2. Always pre-breathe the Explorer Sport Rebreather until the system
passes its’ tests.

3. Do not modify the EXPLORER without the manufacturer’s written con­sent.

4. Do not use a full-face mask, Unless approved by Hollis for use with the
EXPLORER

5. Always analyse your gas.

6. Never dive a unit you suspect is leaking and has not passed all the pre­dive tests.

7. Never leave your BOV open on the surface

8. Ensure your BC is inflated at the surface.

9. Take time to adjust your weight correctly, do not dive over-weighted.

10. Always dive with buoyancy control and buoyancy inflation.

11. Practice a skill on every dive.

12. Avoid unnecessary mask clearing.

13. Regularly sanatize the unit.

14. Never exceed the CO2 alarms.

15. Never hold your breath

16. Never start a dive with a low battery alarm.

17. Always carry bailout gases of sufficient volume for the planned dive as
per your training agency recommendations.

If you do not understand any or all of this section please con­tact your training agency or Hollis.

2 |

IF IN DOUBT BAIL OUT!

BATTERIES

The EXPLORER uses Lithium Polymer batteries. These rechargeable bat­teries are very efficient and provide many years of reliable operation.

Rechargeable Lithium batteries can be recharged at any time and do not
have a significant memory affect, which would otherwise cause unreliable
battery operation. The batteries are UL listed (flight safe) and are double
sealed to reduce the chance of leakage to a minimum.

As extra confidence, the LSS Module battery pack includes 3 separate
batteries to ensure operation even under multiple battery failure scenarios.

During diving the battery reserve alarm will indicate when there is still suf­ficient battery to allow a return to the surface with a small reserve. The unit
MUST then be charged prior to diving again.

1.2

The handset has its own battery that is charged from the EXPLORER Mod­ule automatically.

The user should keep the batteries recharged and topped up to ensure
there is always maximum capacity for any dive.

A fully charged battery pack will display 1000 minutes of battery life.

!

DANGER: The battery estimate is based on current tempera­ture, light usage on the handset, DCP setting and other vari­ables. Changes in conditions (i.e. cold water) may shorten burn
times. Plan dives accordingly, and always monitor the HUD and

Wrist Displays for system operation status.

NOTE: The EXPLORER must be fully charged before its rst
use. Always dry the Optocon charge connector before attach­ing the charging connector. Damage may result if this is not

done.

Check that all parts of the charger are kept dry and only used indoors.

Battery level alarms will activate when the batteries get low. When Battery

level alarms will activate when the batteries get low. When a battery low

alarm is activated this will be displayed on the Status screen.

WARNING: DO NOT dive a battery level, which is less than

!

twice your expected dive time for the next dive.

| 3

1.3

ASSEMBLED UNIT

4 |

Cover Removed

1.4

| 5

1.5

GAS FLOW

As the diver exhales gas flows through the hose (blue arrow) and over the
right shoulder. It then enters the absorbent filter and flows across the Ox­ygen and CO2 sensors in the Sensor Module and through the inhale hose
(red arrow) and back to the mouthpiece.

Gas also naturally flows in and out of the exhale and inhale counterlungs.

Electronics

Inhale

Counterlung

O2 & CO

Sensors

BOV

(Bailout Valve)

2

Absorbent

Filter

Filter

“In - Out”

Indicator

Exhale

Counterlung

6 |

Mechanical Features

The EXPLORER is an electro-mechanical rebreather. Over time certain soft­ware and hardware optional extras and/or software upgrades will become
available. Please check www.HollisGear.com for details.

HARNESS/BCD

EXPLORER uses a custom bolt fitting, backplate, Solo webbing harness,
and Hollis C45LX Wing. There is an optional EXPLORER BCD available.

COUNTERLUNG

The EXPLORER comes complete with dual back-mounted counterlungs
(BCL). These are attached to the canister by a screw threaded O-ring
fitting.

1.6

CYLINDER

EXPLORER uses a 5L/40cuft cylinder with an inline valve. Dives over 18
m/60 ft requires that an additional bailout cylinder of a minimum capacity
of 3 L/20 cuft be used in conjunction with the 5L/40 cu ft cylinder.

USA Only Cylinder Options Chart

Capacity Working pressure

Manufacturer WC (L) WC (CU/FT) BAR PSI

Beever (Eurocylinders) 5 41 232 3410

Luxfer (US) 4.9 40 204 3000

Catalina 4.3 35.26 204 3000

Faber 5 41 232 3410

Faber 6 49 232 3410

NOTE: The Explorer can accomadate a maximum 5.5 in/14 cm
diameter tank.

| 7

CC

OC

EU Only Cylinder Chart

Capacity Working pressure

Manufacturer WC (L) WC (CU/FT) BAR PSI

Faber 5 41 232 3410

Beever (Eurocylinders) 5 41 232 3410

OUTER CASE

The outer case is made from high impact plastic.

OVER-PRESSURE VALVES

EXPLORER uses a combined water release and balanced Loop Control
Valve (LCV). The balanced valve ensures that, the underwater release
pressure is near-constant in any orientation. When the unit vents it also
removes any water from the exhale counterlung. This is best conducted in
a heads up position.

In addition there is a master (high flow) over pressure release valve that is
set to 40mb to help control ascents.

BOV (BAILOUT VALVE)

EXPLORER comes with a BOV. The BOV attaches to the on-board nitrox
circuit. The BOV is designed as the primary bail out (providing a sufficient/
planned volume is carried).

The BOV has two modes (Fig. 1.1):

• OC (Open Circuit Position)

• CC (Closed Circuit Position)

When the mouthpiece is open, the BOV is in the closed circuit position and
when the mouthpiece is closed it is open circuit position.

INTELLIGENT HUD (HEADS UP DISPLAY) & BUD (BUDDY UNIVERSAL
DISPLAY)

The Intelligent HUD (Heads Up Display) is attached to the BOV in the div­ers line of sight. There is also a BUD (Buddy Universal Display) display in

Fig. 1.1

8 |

the EXPLORER Module for Dive Buddy/Instructor use.

These displays give full alarm status at all times using a visual and a tactile
alarm system.

SENSORS

The EXPLORER uses 3 oxygen sensors and one gaseous CO2 sensor. It
also uses a wireless HP sensor.

All sensors are automatically calibrated by the electronic control system.

1.6

| 9

out of the box

initial assembly

The parts to assemble your EXPLORER include:

1. The Front Case

2. The Back Case

3. The Canister (pre-assembled in the Case Front)

4. The Sensor Module (Pre-assembled into the Canister)

5. The Life Support System (LSS) Module (Pre-assembled into the Canis
ter) secured in the system case

6. The Right Hand End Cap (Pre-assembled into the Canister)

7. The Regulator First Stage (Pre-assembled in the Case Front)

8. The Buoyancy Control Device (BCD)

9. The 5L/40cuft SCUBA cylinder and valve

10. Two Breathing Hoses

11. The combined Dive-Surface Valve (DSV) and Bail-out Valve (BOV)

12. The Absorbent Filter (pre-assembled into the Canister – User Pack
version only)

13. One Exhale counterlung

14. One Inhale counterlung

15. One Loop Control Valve (LCV) counterlung port/tube

16. Three Oxygen Sensors

17. One CO2 Sensor - Optional

18. One power charger

ASSEMBLY

Step 1.
Remove all parts from the split top box.

Step 2.
Undo the rubber latches at the base of the Case Front/Back assembly and
lift up the Case Back until the hinge at the top is free (Fig. 2.1). Place to
one side.

Fig. 2.1

10 |

Step 3.
Open the box with the Oxygen and CO2 sensors in it. Remove the sensors
from the box and open up the airtight bags.

DANGER: All sensors must be allowed to sit in an AIR atmo-

!

sphere for at least twelve hours prior to use in the EXPLORER.
The Sensors can be immediately assembled into the Sensor
Module but this module should not be fully installed for at least
12 hours after unsealing the sensors packages.

WARNING: After an initial calibration and dive the sensors

!

should be calibrated again after 24 hours.

Step 4.
Remove the LSS Module by turning the lock ring ½ turn counterclockwise.
Note the orientation in the Canister.

2.1

Fig. 2.2

Visually* inspect the large sealing O-rings for damage (Fig. 2.2).

Pull the Sensor Module out from the Canister.

Remove the yellow and black CO2 sensor filter cap as shown below (Fig.

2.3). This is a simple O-ring push fit and is retained in place once the Sen-

sor Module is assembled into the Canister, as are all the oxygen sensors.

Push the three oxygen sensors and one CO2 sensor onto their respective

connection points as shown in the picture below.

NOTE: Ensure the oxygen sensors are installed with the white

membrane facing up, as shown.

Inspect the the yellow membrane in the CO2 sensor cap to ensure it's flat in

the holder. Then replace the Sensor Module, and refit the cap (Fig. 2.4).

Fig. 2.3

* The O-ring pick is used in the photo for illustration purposes. It is not
necessary to remove the O-ring before every dive.

Fig. 2.4

| 11

Step 5.

Move the LSS module to one side and peel the Optocon charging/

download connector protection cap off as shown (Fig. 2.5).

Plug in the power charger. You will need to rotate the cable end

connector until the key way aligns. Then push it in and tighten up the

black lock ring. The lock ring will spin freely once the connector is ful-

ly assembled. Once connected and power is applied then a red light

will appear on the Electronic Head.

To remove unscrew the ring (which will rotate freely until pulled back

to start the thread) and pull out the connector.

When charging, a Red light appears on the LSS Module. It turns

Fig. 2.5

Green when the LSS Module if fully charged. A full charge takes ap-

proximately 10 hours.

EXPLORER has 3 battery status displays with the charger connected:

1. Battery Charging (Empty) (Fig. 2.6)

2. Battery Charging (Fig. 2.7)

3. Battery Charged (Fig. 2.8)

Once fully charged the LSS Module can be refitted to the Canister.

Fig. 2.6

Fig. 2.7

Fig. 2.8

12 |

To view the charge status of your EXPLORER, do the following:

CC

OC

1. Remove the charger (if attached).

2. Do a long hold of any button on the handset and the Hollis splash

screen (Fig. 2.9) will display. This screen will timeout after 3 seconds

and the "Do Predive" screen (Fig. 2.10) will display.

3. Continue to do a short push of the either button until you see the

central window change to battery status (Fig. 2.11).

WARNING: DO NOT start a dive with a battery minutes display

!

of less than twice the dive time you intend to do. The Pre-dive
sequence will fail if the battery minutes are too low.

2.1

Fig. 2.9

Fig. 2.10

Step 6.
If required attach the BCD to the Case Front using the screws supplied.
Connect the LP inflator hose.

Step 7.
Inspect the mushroom valves in the BOV and make sure they are in place.
Put the BOV into the CC (Closed Circuit) position (Fig. 2.12). Look into one
side of the BOV at the mushroom valve. If you can see daylight through the
other side of the BOV then the valve is not seated correctly.

With the BOV lever in the Closed Circuit position, breathe off the BOV and
ensure the mushroom valves function correctly as per the instructions in
the ‘BOV Assembly’ subsection in the "Complete Disassembly & Reassem­bly" Part of this manual.

Attach the regulator LP hose to the BOV and gently tighten the nut

to the hose inlet (Fig. 2.13, item C). After inspecting the hose end

O-rings, attach the breathing hoses to the BOV. Ensure the white hose

end goes to the inhale side (Fig. 2.13, item B) of the BOV.

Fig. 2.11

Fig. 2.12

A B

C

Fig. 2.13

| 13

Fit the breathing hose alternate ends to the Canister. Ensure the white

hose end goes to the white coded Canister port.

Confirm the ADV LP feed hose is fitted correctly and tightened to a

torque of 50-60 in-lbs/5.6-6.7 N-m (Fig. 2.14).

Step 8.

Remove the Counterlungs from the packaging. Visually inspect them

for damage.

The Exhale counterlung (Fig. 2.15) is the one with the mushroom valve

in the base (this valve is seated in the LCV port).

The LCV port cap is removed by a ¼ turn counterclockwise. This gives

access to the mushroom valve. Inspect the mushroom valve and LCV

Fig. 2.14

port O-ring and the Canister port O-rings for damage (Fig. 2.16).

Attach the LCV port cap to the counterlung. Twist the cap until it clicks
shut.

If not already installed, attach the LCV tube open end to the LCV on the

Canister, using the clip provided (Fig. 2.17).

Fig. 2.15

Fig. 2.16

14 |

Fig. 2.17

Inspect the Canister port O-rings on the Inhale counterlung and attach the
counterlung to the Canister. The assembled orientation of the Counter­lungs and the LCV tube should be as shown (Fig. 2.18). The LCV tube is
on the underside of the counter lung in the figure and is not visible.

Step 9.
Remove the Right-hand End Cap by twisting the lock ring ½ turn counter­clockwise and visually* inspect the sealing O-ring (Fig. 2.19).

2.1

LCV

EXPLORER can be used with two types of absorbent filter:

• Professionally pre-packed

• Single use Pre-packed

The Professionally pre-packed version can be filled with granular absor­bent by a qualified dive professional (see you Instructor or Hollis dealer
for more information).
The Single Use pre-packed version comes in a sealed bag and the filter
CANNOT be taken apart or refilled.

NOTE: If the unit is supplied with a Professionally pre-packed
absorbent Filter then this will be assembled inside the Canis­ter. Reach into the Canister and pull out the Filter by grasping
the central (yellow) pull-tab.

Inspect the Filter quad-ring for damage. Clean the ring groove and the ring
and lightly grease the ring before refitting (Fig. 2.20).

WARNING: This Quad Ring should be replaced every 30 hours

!

of dive time or annually whichever comes sooner.

NOTE: The Single Use Pre-packed Absorbent Filter comes
supplied in a sealed bag and is available from your Hollis deal-

er. This also has a quad ring tted, which must be inspected

prior to use.

Fig. 2.18

Fig. 2.19

Fig. 2.20

For Professionally pre-packed systems, pack the Absorbent Filter as per
instructions.

Insert the scrubber into the canister, and seat it by pressing it into position.
Then refit the end cap by aligning the tab on the end cap and pressing in

* The O-ring pick is used in the photo for illustration purposes. It is not
necessary to remove the O-ring before every dive.

| 15

on the clear center. While pressing firmly, twist the lock ring to 3 O’clock
with your fingers until fully closed as shown (Fig. 2.21).

NOTE: The Case Back will not t and lock properly if the end
cap lock rings are not in the correct orientation.

Step 10.
Fit the SCUBA cylinder. Ensure the HP hose fits into the slots in the case
under the cylinder. Tighten the cam strap.

Inspect the HP DIN wheel O-ring for damage and attach the DIN wheel.

Step 11.
Attach the HUD to the HUD bracket and fit the hose wraps as shown (Fig.

2.22).

Fit the LP hose wraps as shown (Fig. 2.23).

Step 12.
Refit the Case Back and secure the two clips at its base (Fig. 2.24).

WARNING: Ensure that the counterlungs are not pinched

!

during installation of the Case Back. Pinching counterlungs

could puncture or cut the counterlungs, leading to ooding and

risk of drowning.

Step 13.
Turn on the wrist display by doing a long hold of either buttons.

Complete the pre-dive sequence as instructed.

Fig. 2.21

Fig. 2.22

16 |

Fig. 2.23

Fig. 2.24

Life Support System (computer)

General Operation

The EXPLORER Life-Support System (LSS) is designed around a breathing
loop, high pressure gas sources and electronics control system - all highly
integrated to give an intelligent but simple display of status to the diver
while providing life-support.

This gives the user a simple "Check-and-Dive" functionality that makes the
EXPLORER the easiest Rebreather to prepare for diving, while ensuring
system integrity and improving safety.

It uses intelligent monitoring and design experience to determine the
appropriate tests and checks that the diver needs to perform to get the
EXPLORER ready for use.

Any problems are described clearly on the STATUS screen with the re­quired action.

The integrated system design means that failures or problems with any
part of the system are communicated to the diver, either in pre-dive checks
and procedures, or as data values/graphics or instructions. There is sig­nificant background analysis that produces a warning system sensitive to
changes in expected levels, but intelligent enough to not confuse and over
load the diver with information and situations that may be routine during a
dive. These electronic alarms combined with varying levels of mechanical
user controls ensure the LLS is maintained.

3.1

Examples:

• PPO2 changes that may normally cause PPO2 alarms to be triggered are
inhibited if they are of the correct characteristic expected during a descent
or setpoint change.

• There is a significant amount of mechanical design required to achieve
a moisture tolerant breathing loop that reduces distortion of the readings
from the PPO2/CO2 sensors to a minimum. The reliability of the PPO2
readings is further improved by employing a voting algorithm for the PPO2
sensors that can ignore data from rogue sensors.

The EXPLORER design is simple to use but this simplicity does not mean
that the system is simple in terms of data processing or control analysis.
The EXPLORER includes many levels of warning and system analysis,
simplified through experience and intelligence to provide a straightforward
human interface that does not routinely overload or annoy with status or

| 17

false warnings.

It takes considerable system intelligence and design experience to ensure
the warnings do not overload or falsely advise the user of problems. If
falsely warned too many times, then there is a reduced likelihood of the
diver responding correctly to a truly dangerous and potentially life-threat­ening situation.

Mechanically it is vital that simple mechanical tasks required to set up the
EXPLORER are not ambiguous and prone to user error.

THE HEADS UP DISPLAY

The Heads Up Display (HUD) is an ergonomic addition for the diver, as it
gives a simplified and quick to follow view of the status of the EXPLORER.
The HUD as 3 main warning levels:

• Flashing Red plus vibration alarm - warning is activated when a dive
should be aborted on open circuit or not started.

• If diving, the diver should switch to the bailout gas.

• The HUD vibration alarm will vibrate every ¼ second for 10 seconds, and
then repeat the 10-second alarm every minute.

• Flashing Green and Blue Leeds - warning is activated when a manage­able error situation is in place. The correct response is to ascend slowly on
closed circuit monitoring the Primary display.

• Solid Green - means there are no detected problems

WARNING: If any other light sequence or a ‘no light’ scenario is

!

experienced then the diver should refer to the wrist display for

information.

WARNING: If no wrist display is seen the diver MUST switch to

!

open circuit and ascend.

The LED states are configured for color blind as well as highly stressed div­ers. The positions of the LED’s, the flashing or solid state, provide condi­tions that cannot be confused with one another. Also, during stressful dive
scenarios, the position and status is quick to comprehend and therefore
intuitively the desired response is performed.

18 |

PRE-DIVE CHECKS

With current technology, not all aspects of the safety and working nature
of the EXPLORER system can be performed or determined automatically.
Therefore, when turning on the EXPLORER, there are a series of pre-dive
checks that must be performed. The EXPLORER also gives guidance in
performing these checks. These checks are displayed in sequence on the
EXPLORER wrist display unit. Some of these checks rely completely on
the diver to perform them correctly – i.e. Close/open mouthpiece. Other
tests can be positively checked for by the electronics control system and
the user needs to confirm that these are OK to dive with – i.e. that the high
pressure cylinder is adequately filled.

Information regarding the current status of EXPLORER and all available
resources can be reviewed prior to conducting Pre-Dive Checks using the
STATUS screen.

DATA LOGGING

EXPLORER has a sophisticated data logging system that not only records
all the units’ sensors (depth, time, PO2; etc.) but also records any alarms
and error messages (such as missed Pre-dive checks). This information
can be retrieved through the data download software and is available in
detailed form to Hollis Service Technicians.

3.1

Users can obtain dive download software from http://hollis.com/support.
asp.

STATUS SCREEN

The EXPLORER has two levels of detailed information available to the diver.
The primary method is via the STATUS screen. There is an additional set of
STATUS screens in service mode, described in the section 6 of this chap­ter.

The STATUS screen shows as soon as the EXPLORER is turned on (Fig.

3.1).

Fig. 3.1

| 19

In addition, it can be viewed at any point on the dive by pressing any
button and selecting STAT from the pop-up menu using a short push of the
right button. It can also be accessed in service mode by selecting STAT (a
short push of both buttons) from the Startup screen. Note that in both cas­es the STAT button indication is colored blue, as are all button indicators
modified by service mode.

Once in the STATUS screen, a short press of the left or right button scrolls
round the information options. These are:

a. PPO2 (average of the 3 sensors)
b. CO2 sensor
c. HP gas
d. Battery life
e. No Decompression Limit (NDL)
f. Decompression Information
g. Filter (CO2 filter)
h. CNS
i. A general Warnings Window (the ACTION Panel) detailing any alarm in
progress. This mostly displays ‘SYSTEM OK’ or ‘DO PREDIVE as in the
above example unless there is another fault to report.

SERVICE MODE

Fig. 3.2

Fig. 3.3

Service mode is accessed in the Setup Menu.

With this mode set, each pre-dive screen shows additional text information
relevant to the test being performed.

Also, it enables an extra (blue) STAT button on the Startup screen (Fig.

3.2), which if selected with a long push of both buttons (not indicated), will
allow access to detailed service sub-screens. Your Hollis dealer will use
information on these screens to assist with any servicing required. A short
push of STAT will just display the STATUS screen and relevant resources
as during a dive.

To enable fault diagnosis put the EXPLORER into Service Mode. Having se­lected STAT with a long hold of both buttons from the Startup screen you
will access two extra screens (Fig. 3.3, 3.4) (plus alarm and metric screens,
not shown).

20 |

Fig. 3.4

During Pre-dive additional information will be displayed on each Pre-dive
screen such as the PO2 and internal loop pressure (Fig. 3.5).

Your Hollis dealer may need access to this information to help with any
issues. Please see the separate EXPLORER Service Manual for details.

STATUS SCREEN COLORS

3.1

There are four color states of the STATUS screen. Each color provides
additional information. The four color states are:

Green - No problem with the information

Yellow - The system is informing you of a low level alarm such as low

HP gas supply. The STATUS Screen’s Action Panel will give information
regarding the warning or action to be taken and in the case of the low HP
gas example, the value in the HP window will also be in yellow. This will
result in a flashing Green/Blue HUD

Magenta - indicates unreliable data on the reading being taken. This could

be caused by a failed sensor (such as a low wireless HP battery). This will
be coupled with an action to be taken displayed on the STATUS Screen’s
Action Panel. This will result in a flashing green/blue or red.

Red - A major alarm Indicating that information/resource has now become

critical forcing, an open circuit bailout. OC Bailout will be displayed on the
STATUS Screen’s Action Panel and the HUD will flash red and a vibrating
alarm will sound in the mouthpiece

From the Main Dive Screen a double press of the right button will bring up
the STATUS screen (Fig. 3.6) so that the user can determine at a glance
the status of the system while doing a check. This can be useful to deter­mine why a check is not working correctly.

Fig. 3.5

Fig. 3.6

| 21

AUTOMATIC TURN ON

FAILSAFE FEATURE

Normal practice and training is for the user to turn the EXPLORER on by­hand and go through the pre-dive checks. The following failsafe additions
are to reduce diver error, where the EXPLORER is turned off prior to breath­ing on the unit. The basis for the auto-breathe software is to reduce the
chance of accidental injury or death by breathing on an EXPLORER that is
in off/sleeping state.

EXPLORER uses detection of a diver breathing the unit to automatically
turn the unit on.

BREATHING DETECTION TURN ON RULES

The EXPLORER will turn on if PPO2 drops to 0.17bar. Therefore even with
the unit incorrectly assembled (gas not turned on), the system will detect
the fall in PPO2 and will activate. It will then alarm and force the user to
properly complete the pre-dive sequence.

Once turned on the unit will attempt to maintain a breathable PPO2 based
on the DCP (Dive Control Parameter) setting and the supply gas expected.

If sensors are removed or read 0.00 then the unit will only turn on with
depth or by the user pressing a switch. This feature is included to conserve
battery power when the user takes out PPO2 sensors for storage or during
transport. Other current rebreather designs and CE approvals require a
reduced safety margin than achieved even with this power save scenario.
In other words, the chance of the user taking out the sensors and acciden­tally not turning the unit on before breathing falls into user set-up error that
should not routinely occur due to training and a good pre-dive check re­gime. Other errors such as failing to turn on cylinders, etc. are much more
likely, and should be reduced by proper training and the intelligent alarm
systems as in the EXPLORER.

If the diver does not have HP gas turned on, alarms on the HUD (forwards
and rear facing HUD) and Primary display will occur as soon as auto turn­on occurs. Hence this method provides increased warnings whenever loop
PPO2 is breathed when the unit is off.

22 |

Breathing the loop, in all circumstances where the unit is breathable and
PPO2 sensors operative, will cause a safe turn-on.

!

DANGER: The additional safety features described in this
section should NEVER be used as routine. The user should
ALWAYS turn on the unit and pre-dive checks carried out as
required in training and the operations manual.

3.2

| 23













3.3

Display Symbols

Most screen commands (soft buttons) are actually the written word (in
English) but movement commands are expressed using icons.

Moves the cursor to the next field to the right to edit or

moves the STATUS display one window to the right.

Moves the cursor to the next field to the left to edit or moves the

STATUS display one window to the left.

A single bracket indicates a short push of the button to perform

the action (in this case move left)

A double bracket indicates a short push of both buttons to

perform the action (in this case move to left)

Moves the cursor up to the next option (as in a menu list). In this
case a short push of the left button. A down arrow moves the
cursor down.

A short push increments the information by 1 digit. A long push
increments the information in multiples. A minus sign (-)
decrements the digit.

EXITS to the previous page and SAVES the information.

ENTERS the selected item/page

A double bracket around a function indicates a long push

of both buttons. In this case to exit the page.

24 |

SCREEN ICONS

During the Pre-dive tests icons appear across the top of the screen starting
on the left.

As each level of Pre-dive is completed successfully a green icon appears
indicating the test has passed successfully.

Note that all icon colors, as with any numerical displays, match the alarm
severity – yellow indicates a blue/green HUD state. In addition, a grey icon
indicates a test not yet performed.

WARNING. A red icon means a failure of the test/alarm which if

!

ignored would make EXPLORER unsafe to dive.

The icons are:

3.4

Battery &
Computer

O2
Sensors

HP Gas
Content

HP Gas
Analysis

Breathing
Loop

CO2 Removal
System

| 25

3.5

DIVE SCREENS

Screen Description

Dive
Time

Dive Screen
(when ascent rate bar is ½ full then
rate is 30 ft/min

10 m/min)

Dive Screen with menu bar
(accessed by a single push of any
button)

Status Screen
(accessed by a short double push
of the right button)

DCP Auto Mode
(short push of both buttons to
change modes)

DCP Manual Mode
(short push both buttons to change
modes, 1% increment change by
short push of either button, 10%
increment change by long push of
either button)

26 |

status screens

The Status (STAT) screens show all key resources in a simple format.
The screen is accessed from the main screen by a short double push of
the right button, and then a short push of either the left or the right button
moves around the screen. The Status screen also incorporates a color
coded Action Panel to give instructions.

The items that can be displayed are:

Screen Description

Battery time in minutes

CNS oxygen toxicity time in min­utes

3.6

Partial pressure of carbon dioxide
in millibars

Carbon dioxide absorbent filter
estimated remaining time

High pressure nitrox gas supply
remaining in minutes, at current
depth and workload

Any decompression information

NOTE: The Status screen disappears after 5 seconds of inac­tivity (if no alarms) or 30 seconds if an alarm is present. Alter-

natively a long press of both buttons will ‘Hide’ the screen.

| 27

MAIN MENU

MAIN MENU SCREEN (FIG. 3.7)

The EXPLORER has a simple menu system which is available while at the

surface. To access the Main Menu short press any button.

MENU NAVIGATION

Action Button Press

Enter Highlighted

Short push both buttons

Menu Item

Exit Long push both buttons

Scroll Down

Scroll Up

Short push right button

short push left button

MAIN MENU OPTIONS

SETUP

Setup is a basic settings menu. See the following Setup Menu section for
further details.

NDL PLAN

It is a dive planner based on current tissue state, surface interval, and a
DCP setting for the next dive (Fig. 3.8).

PC LINK

Fig. 3.7

Fig. 3.8

Fig. 3.9

This screen is a gateway to updating the internal software and download­ing the log information to a PC (Fig. 3.9). Further details can be found in
the Internet Reprogramming section of this manual.

LOGBOOK

The Log Book screen is where you access recorded information on previ­ously completed dives (Fig. 3.10).

28 |

Fig. 3.10

ABOUT

This screen shows information about the software installed in the EXPLOR­ER, the serial number of each connected element, and information that
may be required by your service center. Software updates for the EXPLOR­ER are available from http://hollis.com/support.asp. Please check regu­larly for updates. Once a new update has been installed, this screen will
report the new version of software installed (Fig. 3.11).

3.7

TURN OFF

This selection shuts down the Explorer electronics.

Fig. 3.11

| 29

setup menu

MAIN MENU SCREEN (FIG. 3.12)

The EXPLORER has a simple menu system which is available while at the

surface. To access the Main Menu short press any button.

MENU NAVIGATION

Action Button Press

To Make A Change

Short push both buttons

(enter the modification
screen)

Exit The Menu Long push both buttons

Scroll Down

Scroll Up

Short push right button

short push left button

SETUP MENU OPTIONS

UNITS

This option allows for the switching between metric and empirial unit
modes.

LOGGING INTERVAL

This option allows for the selection of how frequently the computer takes
a snapshot of dive data, stored for later download. Using a shorter interval
results in more data points per dive and fewer stored dives for download
data respectively. Longer data intervals result in fewer data points (less
detail) but the space to store more dives.

Fig. 3.12

TIME/DATE

This is the clock and calendar setting (Fig. 3.13).

NOTE: When the EXPLORER is rst powered up from a at
battery you will be asked to update the date and time.

30 |

Fig. 3.13

DEFAULT GAS (FIG. 3.14)

Set this to your normal dive gas. During the Pre-dive if EXPLORER ana­lyzes a different gas, it will alarm and ask you to recheck the analysis. For
further detail on proper use of this function see the following section "Bail­out and Gas Configuration".

HP PAIRING

3.8

To pair the HP transmitter, first press SEARCH, any transmitters in range
will be displayed. Then press PAIR. The word PAIRED will appear once the
transmitter is recognised (Fig. 3.15). The transmitter ID is written on the
transmitter attached to the first stage in your EXPLORER (Fig. 3.16). Please
confirm this is the correct transmitter.

NOTE: The HP transmitter MUST have pressure applied to it
to activate and be seen by the system. If the regulator is not
pressurized the the transmitter will be off and not sending a
signal.

Fig. 3.14

Fig. 3.15

Fig. 3.16

SERVICE MODE

Service Mode allows access to more detailed information about the

EXPLORER. It can be accessed by your Dealer. A separate Service

Manual is available through www.HollisGear.com.

| 31

3.9

Bailout and Gas Configuration

DEFAULT GAS SETTING

The EXPLORER has the capability to analyze the dive gas attached to the
system. If this gas differs significantly from what the EXPLORER expects
(the programmed Default Gas), then a warning will be given during the pre­dive sequence. This is to help protect against absent or faulty gas analysis
by the gas supplier and user.

To change the Default Gas, when the unit turns on, go to the SETUP menu
screen and highlight Default Gas by repeated short presses, then a short
push of both left and right buttons to select (Fig. 3.17). The gas can now
be set.

The Default Gas information is used to drive bailout gas calculation (using
cylinder size) and hence gas time remaining and when the unit performs
its gas analysis checks, if the gas analyzed is not the default gas then a
warning will display to prompt you to re-analyze the gas or calibrate the
oxygen sensors.

Fig. 3.17

If the analyzed gas is not what you expected (the Default gas) but is still
usable you can simply start the dive without having to change the Default
gas but you must change the cylinder size if it is incorrect. If the analyzed
gas is lower than expected (within 5%), then it will replace the gas used,
else the default gas will be used.

On this screen you can also input the cylinder size.

!

DANGER: It is important that the correct cylinder size is en­tered for EXPLORER to correctly calculate the remaining

resource times.

BAILOUT GAS

It is not necessary to set a bailout gas. Whether the bailout is under­taken on the onboard (attached) gas or on an external gas supply, the

EXPLORER assumes 21% oxygen and 79% nitrogen as the bailout
gas. This is to ensure as safe an ascent as possible in an emergency. All

bailout decompression calculations are based on 21% oxygen and 79%

nitrogen.

32 |

DCP (Dive Control Parameter)

3.10

DYNAMIC PO

2

The EXPLORER is a dynamic PO2 controller. This means it can vary the
PO2 that it maintains based on the value of certain resources. A higher
DCP (Dive Control Parameter) value means less decompression (higher
PO2) but more gas usage and a lower PO2 is the opposite. For a set DCP
the actual PO2 will vary throughout the dive profile.

The DCP can be set to AUTO or MANUAL mode.

MANUAL MODE

In manual mode the diver can set the DCP using the screen shown (Fig.

3.16). A long hold of either the + or - button will jump the DCP value by 10.

AUTO MODE

AUTO mode automatically adjusts the DCP throughout the dive to give the
best compromise between maximum NDL and minimum gas usage (Fig.

3.19). While shallow (less than 10 m), the DCP will remain at its current val­ue. This defaults to 50% each time the unit is switched on. The first time the
dive exceeds 10 m depth, the DCP will automatically be set high to reduce
the NDL but then as the diver ascends and the NDL naturally increases,
then the DCP will start to automatically reduce to save gas while maintain­ing a long NDL (>1 hr). At the start of the dive the DCP will automatically
set high to reduce the NDL but then as the diver ascends and the NDL
naturally increases, then the DCP will start to automatically reduce to save
gas while maintaining a long NDL (>1 hr)

Fig. 3.18

Fig. 3.19

NOTE: Auto Mode is the default. If on a dive where Manual
Mode has been selected and you then surface and complete
the dive, Auto Mode will be the default at the start of the next
dive.

HOW AUTO MODE WORKS

By setting ‘Auto’ DCP prior to diving the following events occur.

1. The DCP will automatically be set to 95% for the first 10 minutes of the
dive but only after the diver exceeds 10 m of depth.

| 33

2. If the NDL is then less than 60 minutes the DCP will stay set to 95% to
maximize the NDL.

3. If at any point on the ascent the NDL is in excess of 60 minutes then the
DCP will reduce to save gas and maintain the NDL at 60 minutes.

4. The minimum DCP will only go to 105 so if a dive profile means that
even with 10% the NDL is greater than 60 minutes then the DCP will stay at
10%.

34 |

RMS (Resources Management System)

The control of PPO2 is the prime function for EXPLORER in addition it
monitors a range of dive resources. The unit is able to make advanced
decisions based on available resources in order to modify the PPO2 and
provide for a better dive outcome.

The unit constantly monitors all resources such as available gas, filter
duration, etc. and keeps the dive within parameters that allows for a safe
bailout ascent. The unit uses a forward-looking algorithm to determine
the best PPO2 at any given time to avoid or reduce decompression, allow
for a safe open circuit ascent and stay within safe battery and filter dura­tions.

Resources monitored include;

• Depth

• NDL

• PPO

2

• PCO

2

• Battery

• HP gas

• CNS (Oxygen toxicity)

• Filter (CO2 filter)

Fig. 3.20

3.11

Resources are generally expressed in minutes and are noted in the cen­ter of the dive screen (Fig. 3.20).

The controlling (most critical) resource is shown. This can change
throughout the dive and another resource may take its place. Alarms will
be activated when resources reach certain levels as defined in the Alarm
Tables.

In addition, should a resource alarm be triggered for any reason occur
the STATUS screen will appear. This will not only note the resource level
but can also tell the user the direct action required, i.e. ASCEND NOW.

| 35

Oxygen Sensor Calibration

The EXPLORER is able to perform accurate calibration of the Partial Pres­sure Oxygen (PPO2) sensors in ambient air. This has particular importance
on the ease and accuracy of achieving calibrated sensors.

The EXPLORER is able to measure atmospheric pressure during calibra­tion and make the appropriate calibration adjustments for the sensors,
even at altitude. When performing sensor calibrations, it is important that
the calibration gas and ambient pressure are known. By using ambient air

as the calibration gas this is known accurately.

Calibraon Errors

When Oxygen sensors are new or completely dry and a

calibraon is undertaken, a small dierence will be not-

ed when another calibraon is done aer a dive. This is
because the humidity inside a unit post-dive aects the

sensor membranes permeability to a small (safe) degree.

In general, it is good pracce to calibrate a unit in an

as-dived state i.e. with humidity in the loop. This is per-

formed naturally during the Pre-Dive Check sequence.

The EXPLORER uses advanced empirical techniques to ensure the accura­cy of the ambient air calibration.

WARNING: When retting an oxygen sensor or after calibration

of the sensors, a full Pre-Dive sequence MUST be completed.

The user can cause the largest error in oxygen sensor calibration. If the
calibration is not done in ambient air, the sensors will not give the correct
readings after calibration. Therefore do not execute a manual calibration
without ensuring the sensors are exposed to air at ambient pressure.

The units testing for good and bad oxygen sensor calibration is deter­mined from the sensor mV level detected during calibration. At 1000mBar
atmospheric pressure the range the unit can calibrate for is approximately
5mV to 15mV. However, if a sensor that would normally show 7.5mV in air
has an enriched gas applied to it of 40%Oxygen during calibration, then
the sensor will give 14.28mV, and the calibration will pass, but the sensor
will be reading only about half of the actual ambient Oxygen.

36 |

Recommendaons

• Never store sensors for long periods of me before
use; they have expiraon dates.

• Never subject sensors to high temperatures i.e. (inside
cars, garages etc.).

• Never freeze sensors (le in cars overnight).

• Never subject sensors to physical shocks.

• Never subject sensors to vacuum

• Never submerge sensors in liquids.

• Never aempt to open a sensor. They contain a causc
chemical.

• Sensors deteriorate very slowly and near the end of
their useful life may show a dri soon aer calibraon.

• The oxygen sensors are not covered by the warranty,
they must be replaced every 12months or at their ‘do
not use aer’ date or sooner depending on the pp02
they are stored in and the hours of use

• Oxygen sensor usage temperatures are:

- Operang temperature range 0 – 40 °C / 32 - 104 °F

- Storage temperature -20 to +50 °C / -4 - 122 °F

- Recommended storage temperature +5 to +15 °C / 41
°C to 59 °C

3.12

!

DANGER: Always be careful when doing manual calibrations,
AIR must be exposed to the sensors and NO OTHER GAS.

Calibrations should be conducted routinely. However prior to starting

a dive sequence it is advisable to check the oxygen and CO2 sensor

calibration by opening the EXPLORER Module and removing it and

the Sensor Module, place them together (Fig. x.x) and turn the unit on.

Then go to the STATUS screen and view the PPO2 and CO2. If the PO2

is not 0.21 and the CO2 is not 0.3-0.4mb for the CO2, then a calibration

must be performed.

| 37

In general, Oxygen and CO2 sensors do not drift excessively. Constant cal­ibration (every dive) is not required. Periodically check sensors and keep
them dry between dives if possible and especially during storage.

WARNING: Use calibration sparingly, not as a routine task that

!

may mask other potential problems.

CONDUCTING AN O2 SENSOR CALIBRATION

During the Pre-dive sequence you have the option to calibrate the oxygen
and CO2 sensors from the Calibration screen (Fig. x.x). Selecting O2, will
display another series of screens that will guide you through the calibra­tion. Please see descriptions later in the manual for calibrating the CO2
sensor.

SUMMARY OF DO’S AND DON’TS

OF OXYGEN SENSOR CALIBRATION

When calibrang sensors there are two factors that the EX­PLORER takes into account:

1. Ambient pressure

2. Ambient AIR oxygen content

These two factors mulply to determine the paral pressure of
the oxygen exposed to the Oxygen sensor.

Example:

20.9% oxygen at 1000mBar = 0.209mBar paral pressure of
oxygen

20.9% oxygen at 750mBar = 15.675 mbar paral pressure of
oxygen

The EXPLORER uses ambient air as the calibrang gas, because
its composion is accurately known. This is in contrast to say a
cylinder of compressed oxygen that can vary from supplier to
supplier, as well as around the world, from at least 94% to 100%.

38 |

To achieve a good calibraon some basic rules must be ob­served:

1. The Oxygen sensors must be exposed to the pure calibrang
gas. So for an air calibraon, the sensors must be ushed with
air. Just taking the hoses o is NOT sucient, as pockets of gas
can be enveloping the sensors.

2. DO NOT rounely execute calibraons to remedy a rebreath­er that seems to be showing the wrong PPO2. If the rebreather
had previously been accurately displaying PPO2, then some oth­er problem is likely to be the cause. These include:

• Oxygen sensors have become wet

• Current gas exposed to the Oxygen sensors is not what you
think it is.

• The min-jack connecon is corroded

Check the readings on the STATUS screen (average) or Service
Mode STATUS Screen (all 3 sensors).

3.12

If a sensor is reading incorrectly, rst remove it and clean the
mini-jack connector. This can be done with Hollis approved elec­trical contact cleaner or simply by wiping the connector with
a lint free cloth. DO NOT scratch the connector with a metal
instrument. Then look for droplets of moisture on the sensor
membrane. Use a rolled ssue to gently wick any moisture drop­lets from the sensor WITHOUT making contact with the sensor
membrane itself. Pushing on the sensor membrane face can
destroy the sensor.

If neither of these corrects the reading, then the sensor should
be replaced.

The Oxygen sensors vary only slightly over me. Temperature,
atmospheric pressure and moisture have far greater short-term
eects on the readings. Calibraons carried out once a week
should be more than sucient, unless the EXPLORER has been
transported to dierent climates or signicantly dierent ambi­ent condions.

| 39

So, calibraon checks, not actual calibraons, should be car­ried out regularly to ensure the oxygen PPO2 sensing system
is performing correctly. Calibraons should be done more
sparingly, as it takes me to ensure the correct condions are
exposed to the sensors. Oen a bad calibraon causes more
confusing problems than small errors due to temperature
change. User error caused by failure to use the appropriate
ambient gas (air) is a big source of sensor errors.

1. Don't over calibrate

2. If something seems wrong, check everything. Do not just
execute a calibraon to x the reading. You could be making
maers worse.

3. Keep sensors dry.

4. When doing a calibraon, do ensure the sensors are ex­posed to air - force air over the sensors, do not just assume
"they must be exposed to air by now".

5. Just removing hoses is not enough to get air to the sen­sors. Either the breathing roune described in the Pre-Dive
sequence must be used or the Sensor Module should be re­moved from the EXPLORER and sensors allowed to stabilize in
ambient air.

6. If the EXPLORER has had a change in climate or signicant
ambient condions, these are good reasons to check calibra­on.

7. The readings from the oxygen sensors change with tempera­ture. If you are diving in warmer or colder water than normal,

PPO2 readings will vary. Ensure calibraons take place at a

temperature as close to diving condions as possible.

40 |

OXYGEN SENSOR VOTING

VOTING METHOD

The EXPLORER has a method of automatically removing Oxygen sensor
sensors from the PPO2 averaging and entering a fail-safe mode when it is
not possible to resolve an accurate PPO2 reading.

Rules:

1. If a single sensor is below 0.15 bar or above 3.00bar, then it will be
removed from the averaging — a ‘BAD CELL! DO NOT DIVE’ alarm will be
displayed if not diving, or ‘ASCEND! BAD CELL’ if diving.

Diver Action: Ascend on the rebreather

2. If a sensor is less than 7mv then it will be removed from the averaging
— a ‘BAD CELL! DO NOT DIVE’ alarm will be displayed if not diving, or
‘ASCEND! BAD CELL’ if diving.

3.13

Diver Action: Ascend on the rebreather

3. If one sensor is +/- 0.2 bar away from the two remaining sensors then it
will be removed from the averaging — a ‘BAD CELL! DO NOT DIVE’ alarm
will be displayed if not diving, or ‘ASCEND! BAD CELL’ if diving.

Diver Action: Ascend on the rebreather

4. If all three cells are removed from the averaging for the same reason
(i.e., all low or all high), then all cells will be used in the averaging (super­seding rules 1, 2 and 3) — a ‘BAD CELLS! DO NOT DIVE’ alarm will be
displayed if not diving, or ‘ASCEND! BAD CELLS’ if diving.

Diver Action: Ascend on the rebreather unless superseded by rule 7.

5. If the difference between the highest sensor and the lowest is greater
than 0.5bar then the system will inject gas for 1 second out of every 3 as a
fail-safe. This will cause an ASCEND NOW alarm.

Diver Action: Ascend on the rebreather. Rebreather switches to Fail-safe
mode.

6. If the average of all sensors (not removed from the averaging by rules 1,
2, 3 or 4) is greater than 1.6bar when diving then an ASCEND NOW alarm

| 41

will be displayed.

Diver Action: Ascend on the rebreather

7. If the average of all sensors is less than 0.17 or greater than 2.0 when
diving then a BAILOUT alarm will display.

NOTE: This alarm will supersede those in rules 1, 2, 3, 4, 5 and

6.

Diver Action: Open circuit Bailout to surface

8. If two or more sensors are removed from the averaging (because of
rules 1, 2, 3 or 4) then the system will inject gas for 1 second out of every 3
as a fail-safe. This will cause an ASCEND NOW alarm.

Diver Action: Ascend on the rebreather. Rebreather switches to Fail-safe
mode.

EXAMPLES

1. Sensor 1 = 0.65bar, sensor 2 = 0.60bar, sensor 3 = 0.70bar.

→ All sensors used

2. Sensor 1 = 0.3bar, sensor 2 = 0.60bar, sensor 3 = 0.70bar.

→ Sensors 2 and 3 sll used

3. Sensor 1 = 0.3bar, sensor 2 = 0.60bar, sensor 3 = 0.9bar.

→ Failsafe – inject for 1 second out of every 3. {Sensors are greater than

0.5 apart across all 3 sensors (0.3 to 0.9)}.

42 |

CDM (CANISTER DURATION METER)

The EXPLORER Canister Duration Meter (CDM) is comprised of three main
parts:

1. A patented, absorbent temperature profile duration meter.

2. An Oxygen Injection Meter (based on CE tested durations).

3. A gaseous CO2 sensor

The readings from all of these devices together can be used to report a
high confidence status regarding the state of the Absorbent Filter. Howev­er, user experience and training should also be used to determine the va­lidity of the readings given. Absorbent Filters are a key item in the rebreath­er, and prone to miss-use. Great care should be taken when determining if
a dive can be safely performed with the filter in its current state. Flooding,
long time between uses, improper assembly, improper packing can all
contribute to the canister duration meter reporting false readings. Use
great care in assembling the device and in completing pre-breathe checks
on the Absorbent Filter and breathing loop. The CDM is a useful feature as
an aid to predicting absorbent duration.

3.14

WARNING: NEVER dive a partially used Absorbent Filter after

!

24 hours beyond its initial packing or opening irrespective of

the CDM meter reading. This includes partially used lters that

have been stored in a sealed loop or container.

TPM (TEMPERATURE PROFILE MONITOR)

This meter relies upon the heat producing reaction of the CO2 absorbent.
Temperature sensors are used to determine the status of the CO2 absor­bent has been performed in laboratory conditions for many years. The
system detects a complex reaction heat wave front through the absorbent
as it is being used.

The duration of the Absorbent Filter depends mainly on the amount of CO
being produced by the diver and the depth of the dive.

!

DANGER: The TPM will not detect breakthrough conditions of a
poorly packed Absorbent Filter or failing seal. Therefore Pre­breathe checks must always be carried out to ensure CO2 is

being absorbed correctly by the lter.

2

| 43

The TPM contains 5 Thermostats arranged longitudinally through the
canister absorption path. The readings from these 5 thermistors are logged
and analyzed by the system. In this manual, it is not appropriate to explain
this data analysis in detail. However, it is appropriate to describe some of
the limitations of the device.

The CO2 absorbent produces heat when CO2 is absorbed. However, there
is also a temperature rise even when incomplete absorption of the CO2 in
the breathing gas is achieved. This is a potentially dangerous situation, as
the system appears to be working correctly as there is still a measurable
temperature rise and wavefront in the system. The human body is tolerant
to only approximately 5 to 10mBar of CO2 (ref CE standards for a life sup­port system). A well-packed fresh Absorbent Filter absorbs all the exhaled
CO2 for a period of time until an amount of CO2 starts to creep through.
When this level reaches 5mb it is assumed there is no life left in the filter.
However even at 5mb there is still considerable thermal activity within the
filter.

DANGER: So be aware that a well packed and well maintained

!

Absorbent Filter is key in achieving a life-support system. The
CDM is not a substitute for good system maintenance and Pre­Dive checks. Always use your training and discipline to ensure
the sub-systems in the EXPLORER are operating correctly.

Critical components and potential failures are:

• The filter seal around the Absorbent filter

• A poorly packed (user pack only) filter

• Used or out of date absorbent material

44 |

Below is a graph of the data log from a chamber breathing system test
dive. 1.6litres of CO2 are being fed into the system every minute. The
external water temperature is approximately 4 degrees Celsius. It shows
the thermistor readings on an arbitrary scale, canister remaining percent
prediction and depth in meters. The endpoint of the graph is when the CO2
levels reach 5 mBar break through.

3.14

The thermistor curves at the beginning of the dive, as the canister heats

up, have a different shape to the middle to latter part of the dive. It is

not sufficient to simply look for the position of the hottest part of the

canister. This will give poor predictions of canister duration. The algo-

rithm first normalizes temperature difference data. Then uses a tech-

nique to determine which part of the curve the system is on – begin-

ning, middle or end. It then correlates a look-up of the measured data

into the suitable reference data to determine the canister duration.

The filter should always be kept sealed until required for use. Once

installed, the filter should be changed within 24 hours even if it has not

been fully used through breathing. When installed and being unused,

the EXPLORER should have its breathing loop closed so that external

air does not accelerate the degradation of the filter. However, once open

and used, even if only a little, the filter will continue to degrade and

| 45

change its characteristics post-dive. Therefore, as previously stated, the
filter should always be changed within 24 hours of opening and/or use.

Partially used filters should be stored in the EXPLORER with a closed
breathing loop.

Although the algorithm that analyzes the thermistor curve is adequately
accurate during diving, if the filter is not being breathed on, the thermistors
curve will be abnormal. It also takes time for the absorbent to rise to nor­mal operating temperatures. Therefore for routine use, the addition of the
Oxygen injection meter (described in the next section) is used to report the
filter percentage remaining to the user.

OXYGEN INJECTION METER

The CO2 created by the diver is in direct proportion to the oxygen

breathed. The oxygen metabolized by the body is replaced by the in-

jection of oxygen into the breathing loop. By knowing the volume of gas

injected, the amount of metabolized oxygen and therefore the amount

of CO2 created can be estimated. From tests, the duration of the filter

types has been determined and the corresponding volume of CO2 ab-

sorbed before the absorbent begins to reduce its effectiveness.

Using these principles, the system measures the amount of gas injected
by the solenoid valve and converts it to a percentage of minutes remaining
at CE CO2 rates. Although the displayed minutes are at CE CO2 generation
standards, the minutes will tick down more slowly if the diver is breathing
at a reduced rate. This will be the most common scenario. However, in the
unusual condition of CO2 generation at an elevated rate compared to 1.6ltr/
min then the minutes will tick off more quickly. If the diver knows a particu­larly strenuous dive is ahead, they should allow extra conservatism in the
minutes remaining counter, for that dive.

The Oxygen Injection Meter should be used in conjunction with the Tem­perature profiler and the Gaseous CO2 sensor to determine the appropriate
state of the filter. The remaining Oxygen injection meter percent is dis­played on the STATUS screen as a ‘Filter minutes’. The Oxygen Injection
Meter minutes are reset when the absorbent is replaced and confirmed in
the Pre-Dive Sequence.

46 |

WARNING: The CO2 Absorbent Filter Alarm will activate when

!

there is sufcient duration to allow an ascent to the surface

with an additional (approximate) 10 minutes reserve remaining.
At such time, the diver should ascend to the surface on closed

circuit.

!

DANGER: If in doubt of the condition of the CO2 lter, replace
the absorbent and perform full pre-dive checks. Filter time re-

maining must exceed the planned dive time.

OPERATION AND INTERACTION OF TEMPERATURE PROFILER
AND OXYGEN INJECTION METER

The thermistor bar chart of the temperature profile through the filter is

shown to give the diver information on the activity of absorbent inside

the filter. This should have a peak when the filter is being breathed on.

From cold it will take about 5 minutes for the CO2 reaction to cause a

visible peak. This peak should then continue and grow higher. The tem-

perature bars fill from the left to the right as the filter is being used. This

screen is in the Pre-dive sequence.

3.14

If there is no peak, then there is a problem with the filter. This could be

caused by:

1. Flooded filter

2. Filter not fitted

3. Filter empty – all used up

| 47

During pre-breathe, the unit needs to be breathed on to see a change in
the thermal profile. This does not guarantee correct operation, but has a
high likelihood of correct operation. Any sense of dizziness, nausea or oth­er CO2 symptoms should also be used to alert the diver that the filter is not
operating correctly. A small bypass due to a badly fitted filter or CO2 seals
could give this scenario of a good peak, but an amount of CO2 could still
bypass the filter. If this occurs, stop breathing on the EXPLORER. This will
be indicated (and alarmed for) by the Gaseous CO2 sensor. Replace the
absorbent and/or check filter packing and seating.

CAUTION

CAUTION: Pre-breathing any rebreather should be done in
a safe seated position where the diver can monitor displays
and any potential symptoms of CO2 poisoning. Pre-breathing
should never be conducted while walking or standing in a place

where the diver could fall into the water or injure him or herself.

The actual minutes remaining number displayed to the diver comes from
the Oxygen Injection Monitor. This gives a consistent and reliable reading
of current absorbent duration based on Oxygen injection.

Always remember to reset the absorbent duration when a new filter is
fitted. You will be prompted to do this during the Pre-dive sequence (Fig

3.21).

DANGER: DO NOT reset the absorbent duration unless a new

!

lter with fresh absorbent has been tted.

Always change the absorbent when the low filter alarm appears, or before
if you suspect the absorbent is not operating correctly or close to the end
of its life - be conservative - be safe.

!

DANGER: If an absorbent lter is not tted, the green central

indicator will not be visible on the Right Hand End Cap and it

will not be possible to breathe off of the loop.

No matter how many safety monitoring systems are in place, use
your own common sense and discipline to ensure you do not
push the life support systems beyond their designed limitations.
It is your life being supported - respect the equipment and its

limitations.

48 |

Fig. 3.21

CARBON DIOXIDE SENSING MODULE

Premise:
The EXPLORER comes with an option to fit a CO2 sensor. The user can
elect to buy this from new or upgrade to the sensor later. The CO2 sensor
gives many advantages as detailed below.

EXPLORERS not fitted with CO2 sensors or that have had their CO2 sensor
temporarily removed by the user, can still be dived but with no CO2 sensor
fitted a 5 minute pretreated of the absorbent filter will be forced in stead of
the normal 1 minute.

!

DANGER: With no CO2 sensor tted careful monitoring of lter

duration is vital.

There is little confirmed data on actual absorbent durations typical for sport
diving rebreather use. Sports divers often push the absorbent duration be­yond the published CE durations, because they assume that they will not
be creating as much CO2 as the CE trials or operate at the same tempera­ture or depths.

3.14

The problem can arise that if a diver has gone deep and works hard, per­haps to rescue another diver; when the absorbent duration is near its limit,
the extra depth and work rate push the CO2 to dangerously high levels very
quickly.

The CO2 sensor will help by giving feedback in this scenario, and advise
the diver of the high CO2 levels. The diver should then reduce their work
rate and reduce their depth and finish the dive as safely as possible or bail­out to open circuit as indicated. The relatively fast rise in CO2 readings is
also an indication that the absorbent cannot be pushed any harder without
causing even higher CO2 levels.

A question asked already by many divers who have seen the system in
operation, is “Can the CO2 reading be used to determine the duration
remaining in the filter?”

The answer in principle is ‘yes’. However with the current knowledge and
data available, there is no practical system to achieve this. The duration of
the absorbent changes with CO2 generation, temperature, depth, and re-

| 49

breather design. People have achieved over 8 hours duration with relatively
small absorbent loads, but this has been in warm water, with low breathing
rates and shallow depths. It is currently not known what the effects are
when an absorbent filter working at a CO2 level of say 2mBar that has been
used in a shallow scenario is taken deeper and the work rate is increased.
We know that the CO2 would increase, but do not know how fast. In field
tests, we have seen the CO2 jump quickly from 3mBar to 6mBar just by the
diver going deeper near the end of absorbent duration. This same rise will
not occur if the filter is at the start of its life. Forecasting potential duration
with the CO2 sensor will be possible in the future after more development
but this is not currently the main function of the CO2 sensor. Its’ current
functionality is as an active warning device for CO2 absorbent system
issues. It can detect for bad absorbent, no absorbent, high work rates

and general CO2 seal issues.

WARNING: Currently the CO2 sensor reading should not be

!

used as a duration meter for the rebreather. It is vital that it
is used to report and alarm for a high CO2 reading that could

occur with a faulty seal or exhausted absorbent.

Our bodies produce the same CO2 quantities independently of depth. So
just staying shallow does not reduce CO2. It can however; help the CO2
absorbent perform more efficiently. Therefore a low CO2 reading on a filter
that has been used in shallow water for some time may rapidly increase if
(towards the end of its’ life) it is taken deeper or the work rate increases.
Be aware that the CO2 reading can rise dramatically for higher work rates
and deeper depths, especially when an absorbent has been used for over
50% of its recommended duration.

Therefore, in order of priority, the EXPLORER is fitted with a gaseous CO2
sensor, a metabolism ‘click’ counter (providing an estimate of oxygen con­sumed, hence CO2 generated) and a TPM giving an indication of thermal
activity within the filter. These three features give a more accurate indica­tion of absorbent life remaining.

The use of the CO2 readings is four fold:

1. To ensure active absorbent has been fitted

2. To ensure the absorbent sealing systems are operative

3. To warn of reducing absorbent efficiency in order to give the diver time
to respond by reducing depth, temperature or work rate to avoid an inci­dent occurring.

50 |

4. To warn of rare situations when excessively high CO2 levels may require
immediate bailout to safe open circuit gas.

!

DANGER: The CO2 sensor should NOT be used to determine

absorbent duration.

NOTE: As more actual dive data becomes available it may be
possible to model the CO2 curves and generate some level
of prediction of remaining absorbent life. This is currently a

work in progress.

CO2 – CARBON DIOXIDE SENSOR FOR EXPLORER

This section describes the operation of the CO2 sensor as fitted to the
EXPLORER rebreather.

The EXPLORER CO2 sensor is the world’s first commercially available car­bon dioxide sensor proofed and designed by VR Technology for operation
in a high humidity, high oxygen rebreather breathing loops.

3.14

The CO2 sensor actively measures carbon dioxide while the user is breath­ing on the loop. It can thus warn of high CO2 levels before unconscious­ness or other symptoms occur, in time for the user to perform remedial
tasks such as finishing a dive, reducing activity or even bailing out to other
gas sources.

BACKGROUND

It should be noted that this is the first use of a CO2 sensor in an active-user
breathing loop. As such, new data on CO2 levels will be obtained that will
identify areas of adjustment of common practice and improved use of the
CO2 readings as time goes on.

Much of the research in CO2 poisoning has been conducted with military
levels of exertion and requirements. From this research the 5 to 10 mBar
limits for CO2 were formalized as the upper working range for CO2 by a
diver undergoing considerable exertion. Thus the alarm levels within the
EXPLORER have been initially set as 5mB and 10mB. As the user moves
into the 5 mB+ range, although no symptoms may occur, it is highly advis­able that the dive be terminated as soon as possible.

| 51

It is assumed that CO2 levels in the region of 15 – 20mB are potentially very
dangerous and potentially fatal, and the user could easily lose conscious­ness with little or no warning and as such it is potentially extremely danger­ous to work at any CO2 level above the 10mb range.

MAIN FEATURES

The CO2 sensor consists of a proprietary combination of filters and sensors
that together provide a robust CO2 monitoring system for breathing loops
in rebreathers. The CO2 sensor is able to compensate for pressure and
humidity environments as normally achieved in a diving rebreather system.

The EXPLORER version is powered from the LSS Module rechargeable
battery.

The CO2 sensor requires occasional calibration. EXPLORER has a sophis­ticated logging system that minimizes the number of calibrations. It also
removes the need to use CO2 calibration gasses.

WHAT SHOULD I EXPECT TO SEE ON THE CO2 SENSOR READINGS?

As a unique CO2 sensor in an active breathing loop, some user education
is required to understand the benefits, features and limitations of the de­vice. From this standpoint, it is worth the user taking a short time to under­stand more of how CO2 is dealt with in the breathing loop.

CO2 filter endurance is reduced by increased depth, low water temperature
and high work rate (CO2 generation) variables. As the user pushes the CO
absorbent filter towards (or past) the end of its CE tested limits, the levels
of CO2 in the loop may be surprisingly high or could be low if the variables
are less extreme but could accelerate rapidly dependant on the rebreather
design.

Some divers feel they are getting more duration because they are not
producing as much CO2 as that used in CE trials or that other variables are
less extreme within their diving environment.

Information from field use with the CO2 sensor indicates the filter dura­tions are actually quite close to the CE durations and the 5 mB CO2 point.
However, 5 mBar of CO2 is not fundamentally damaging. Metabolism and

52 |

2

respiration can occur to some degree even up to 20mB CO2. However, the
amount of exertion and other pressure related effects mean that this is un­advisable, and CO2 poisoning and death may occur at levels in the 10-20
mB range in some cases. So some of the extended durations currently ex­perienced are due to the user taking the CO2 level into the 5-10 mB range,
without any obvious symptoms of CO2 poisoning.

The user must be aware that strenuous exertion when CO2 is at these
elevated levels can quickly cause the CO2 levels to rise rapidly. As the
symptoms of CO2 poisoning are almost impossible for the user to recog­nize – they will just pass out and may drown. However, the readings from
the CO2 sensor showing that CO2 levels are rising (while still not exhibiting
symptoms) should be used as much as anything to limit the strenuous
activity and further use of the filter after the dive has finished.

!

DANGER: New dives must not be performed on the lter once

CO2 levels in the 5-10 mB region have occurred, regardless of
how short a duration. Some rebreather fatalities are possibly
due to users pushing the CO2 lter with strenuous activity near

the end of the lter life.

3.14

Increased depth or reductions in temperature when the CO2 filter is near
the end of its life are also not advised, as the filter is less able to cope with
high CO2 levels. So increased depth, coupled with muscular activity and
cold are a very bad combination when near the end of filter life where CO2
levels are already raised.

NOTE: Conversely, reducing your depth and work rate and
returning to warmer water, are all good ways to manage CO

2

levels until you can return to the surface and change the

lter. In any event if a CO2 alarm is seen the EXPLORER will

force an immediate action to return you to the surface.

| 53

GASEOUS CO2 SENSOR SYSTEM CONSTRUCTION

The CO2 sensor system comprises of a Sensor and a removable/change­able filter. The basic principle of the system is to use Infra Red technology
to detect carbon dioxide (CO2) in the retreaters’ breathing loop. However
certain contaminants and in particular moisture, will affect the sensors abili­ty to read accurately. To help with this issue, the assembly comes complete
with a user-changeable filter system that can be simply disconnected from
the Sensor Module and serviced by the diver (Fig. 3.22).

DANGER: It is vital that to maintain accurate CO2 readings the

!

performance of the ltration system is maintained and a dry
piece of absorbing material tted before every dive. Calibration
of the sensor must be conrmed periodically by exposing it to

air. CO2 readings in air should be 0.4 ± 0.1 mb. If in doubt then

recalibrate the sensor.

NOTE: Readings in air should be between 0.4 ± 0.1mb.

CO2 FILTER CARE

!

DANGER: For accurate CO2 readings, a clean and dry piece of

absorbent material must be tted prior to every dive. Different

environments will produce different amounts of moisture and

hence the lter change-out routine may vary.

Fig. 3.22

Absorbing

Material

Membrane

54 |

Filter Body Filter Cap

The filter cap attaches to the filter body and is a push fit. The basic con­struction of the filter starts with a specialist filter membrane in the cap (the
yellow material) backed up by a water absorbing material (the central
sponge like material in the picture).

NOTE: The lter cap retains the membrane (yellow materi­al) that must NEVER be removed. The Sensor itself is not a
user serviceable part and damage may result if it is tampered

with. If the lter cap membrane becomes damaged it must be

replaced.

The yellow water absorbing material (center of picture) is removable. The
EXPLORER is supplied with spare absorbing material. Simply remove one
and refit a new one (Fig 3.23).

3.14

The absorbing material will become wet during a dive. The used absorbing
material can be dried out, preferably in an air-conditioned environment, as
it will become moist during a dive.

WARNING: Each absorbing material piece should only be used

!

for a maximum of 10 dive hours or if damage is noted, replaced
immediately or sooner if the readings from the CO2 sensor are
not within the expected range (i.e. almost 0mb at the end of the

Pre-dive sequence with a new lter tted).

DANGER: Failure to replace the absorbing material may result

!

in faulty CO2 readings.

If debris is noted on the front face of the membrane (yellow material) or if
it is suspected that contamination is restricting the flow through the mem­brane, it should be replaced.

Fig. 3.23

| 55

CALIBRATION

During the Pre-dive sequence you are prompted if you want to calibrate
the CO2 sensor (Fig. 3.24).

The ONLY source of calibration gas is fresh air. With the filter removed

and the sensor in fresh air the CO2 reading should read 0.4mb +/-

0.1mb. Leave the sensor exposed for at least 5 minutes. The on-screen

prompts will guide you through the calibration. This involves removing the
exhale hose from the mouthpiece and breathing the unit for one minute to
circulate fresh air into the system.

WARNING: At the end of a Pre-dive sequence with a new lter

!

tted the CO2 readings should be almost 0mb. If this is not the

case then the sensor must be recalibrated (as above) or re-

placed.

NOTE: Post dive, if you want to do another calibration, you

must remove the lter cap to calibrate.

The same system should be used to just check the calibration. There is no
need to constantly calibrate but it is good practice to check the calibration
at the start of a dive sequence using the above method.
Once it is calibrated, to confirm the operation, gently breathe across the
sensor face until the reading changes. Now re-install the filter prior to div­ing.

Fig. 3.24

After calibration and with the sensor inserted into the loop if a full pre­breathe with fresh absorbent is undertaken the CO2 reading should fall to
0mb. This is normal.

Post dive and with no gas flow (breathing) you may see a small rise in CO
levels due to gas density and pocketing. After a pre-breathe this should
stabilize. Blowing into the sensor face may also create the same affect until
it is used again normally in the breathing loop.

WARNING: If at anytime you see a reading that is abnormal you

!

should check the calibration.

56 |

2

Abnormal readings could include:

1. A reading fixed at zero or any other number when you are breathing
directly onto the sensor face with the rebreather disassembled.

2. An abnormally high reading during a dive.

NOTE: Under CE conditions after approximately 50 minutes
at 40 m at 1.6 l of CO2 (very high workload) in 4 °C/39.2 °F it

should read 5 mb.

3. Readings that change up and down (not in one direction). This could

be a faulty sensor or a faulty connection into the Sensor Module.

The CO2 sensor will benefit from calibration at the start of a dive sequence
and if the sequence is longer than 1 week, at the start of each new dive
week. When having not been used for over a month or if you suspect a
bad reading (see additional notes on filter care) a calibration must be done
prior to diving. It is good practice for the user to check the approximate
validity of the CO2 readings regularly, ideally prior to any dive. Simple
testing by breathing directly onto the sensor should see the reading rise
within approximately 1 minute. Also exposure to clean fresh outside air
should give a reading in the order of 0.4 mB. The unit will respond faster
with the filter removed. So the user must familiarize themselves with the
operation and assembly of the system to be confident the device is work­ing correctly. Consult your Hollis dealer if in doubt.

3.14

WARNING: If you wish to calibrate the unit you must ensure

!

you are in fresh ventilated (outside) air. DO NOT calibrate in a
closed room. The calibration method is discussed above and is

detailed step by step in the pre-dive sequence.

ELECTRICAL CONNECTION

The connector for the CO2 sensor is imbedded into the Sensor Module
next to the 3 x O2 sensors.

NOTE: If moisture is present when this connection is mated,
then contact corrosion may occur. This may give false read­ings on the CO2 sensor.

It is vital this connection is kept clean. hollis approved contact cleaner or

| 57

white vinegar and a soft brush can be used to achieve this. Inspect this
connection regularly.

MECHANICAL FITTING

The sensor should be fitted into the EXPLORER Sensor Module.

Check the O-rings around the filter carrier are not damaged. Ensure the
O-rings are lightly greased.

Ensure the absorbing material is clean, dry and not damaged. The filter
assembly should be periodically checked for water or mechanical dam­aged. It is advised to keep spare replacement filters. The filter is the main
protection for the sensor from the breathing loops general environment.
If damage occurs to the filter or it becomes exhausted, then damage will
result to the CO2 sensor itself. So always keep in it good condition.

NOTE: After a days diving, you can remove the Sensor Mod­ule from the rebreather and keep the Sensor Module (and the
sensors) in a dry environment (air conditioning if possible)
until the next dive. Removing the CO2 lter assembly to venti-

late the CO2 sensor is also advised.

CALIBRATION SCREEN

To access the CO2 feature for calibration go to the "CO2 option" in the Pre­dive screens.

WARNING: The CO2 sensor MUST always be calibrated in fresh

!

clean air, outside, preferably at sea level.

Select the CO2 option (Fig. 3.25) and EXPLORER will prompt you through
the setup procedure and calibration will occur automatically.

Always check that the sensor reading after calibration reads approximately

0.4± 0.1 mBar.

DIVE SCREENS

In the Main Dive screen (Fig. 3.26) the CO2 reading is found by access­ing the STATUS screen by a double press of the right button. Then scroll

58 |

Fig. 3.25

Fig. 3.26

through the screens to see CO2.

Scrolling through the screens to the CO2 display will now display the CO2
reading in Millibars in the central window (Fig. 3.27).

CE TESTING OF CO2 SENSOR

Gaseous CO2 sensor module:
Tests conducted at ANSTI test systems.
As can be seen from the graph below, the CO2 sensor readings keep in
close correlation with the ANSTI Teledyne Lab CO2 analyzer. The Blue trace
is the ANSTI detector. The CO2 sensor is represented in pink. The quick
occasional changes to the Blue ANSTI trace are calibration tests to ensure
accuracy of the measured readings.

3.14

Fig. 3.27

KEY:

BLUE = ANSTI

PINK = CO2 sensor
(inside breathing loop)

Y scale = CO2 mbar

It can be seen from the graph that after 60 minutes there is less correlation
between the in loop and ANSTI readings. This is due to the rapid ascent
rate pressure change causing a temporary temperature drop. The CO2
sensor will quickly recover from the temperature drop.

To a lesser extent, there is also the reverse condition at the beginning of
the dive, where the chamber is being pressurized and the temperature is
rising. Within a few minutes the readings are correlated.

| 59

Display & Alarm Systems

HUD, BUD, & COLOR SCREENS

The EXPLORER can be routinely dived by using the HUD (Heads Up

Display) as the main underwater human interface. This frees up the

diver to concentrate on the dive at hand.

The HUD is in the divers vision and attached to the BOV. It utilizes color

LED's and a vibration feature to get your attention when necessary.

Additionally, the EXPLORER has a BUD (Buddy Universal Display) on

the side of the LSS Module for the Buddy/Instructor to see your status

at a glance. Both the HUD and BUD indicate the same color codes.

If the HUD/BUD system changes from Green for ‘go mode’ to a flashing

green/blue then the diver can refer to the main wrist display and

investigate the additional information on the STATUS display.

The wrist display utilizes color as an alert for general status changes

and couples this alert with unprecedented clarity of information that can

be reviewed in further detail.

The HUD, BUD, color screens on the wrist display, and uncluttered

screen layouts are key to providing the diver and dive team with

essential information in high stress scenarios.

60 |

DEFINITIONS

Alarm (state): These are mostly alarm(ing) conditions, but not always. They
could represent a state of the system that is displayed in some way other
than via the HUD or STATUS screens.

Alarm Display: The method by which an alarm state is passed to the user.
On the LSS module, the HUD, BUD, and tactile alarm are used. On the
handset, this is done via the GUI (Graphical User Interface) displays and
the STATUS screen, which also has an ACTION Panel reflecting the HUD
and a message containing a single user action. Some alarm displays vary
depending on other system states, such as other alarms or the dive status
(e.g., diving, not diving).

ALARM CODES

With the EXPLORER, a key task has been to process the fault levels and

error conditions to indicate the status of the rebreather. Further, the LED

states are configured for color blind as well as highly stressed divers.

The position of the LED’s coupled with the flashing or solid states,

provide conditions that cannot be confused with one another. During

stressful dive scenarios, the position and status is quickly understood

to speed up the desired response/correction by the diver. The status

sceens on the wrist display add one more level of security by adding

extra information on an alarm states.

3.15

WARNING: This information is in English, and all users should

!

be adequately trained in interpreting this information appropri-

ately.

| 61

There are 3 main warning levels associated with the HUD, BUD, and

on-screen displays.

Alarm Code Meaning Correct Action

Solid Green This code means there

are no detected prob-

OK - Procede with dive
as planned.

lems.

Flashing Green & Blue
(HUD/BUD)

&

Yellow
(wrist display)

Warning - It is activat-

ed when a manage-

able error situation is

in place.

The correct response

will be displayed on

the STATUS screen

and will often tell the

diver to ascend slowly

on closed circuit

monitoring the wrist

display.

Magenta (wrist display
only)

Loss of communica­tion between sensors
or modules. It is
usually associated with

Check the status and
for any message on
the wrist display an

react accordingly.
DO NOT dive or OC
bailout but could just
be a warning.

Flashing Red
& Vibrating

It is activated when
there is an urgent
issue.

- DO NOT start the

dive.

- If already diving, the

diver should switch

to the bailout gas and

ascend.

NOTE: Red alarms take priority in the HUD over Green/Blue
alarms.

NOTE: Yellow on the display is equivalent to the alternating
blue/green state of the HUD.

NOTE: The HUD vibration alarm will vibrate every second for
5 seconds, then repeat the 5 second alarm every 30 seconds,
or if the source of the alarm changes.

62 |

Alarm flow diagrams

The following sections contain flow diagrams to indicate which actions /
HUD indication will be used separated into diving and surface cases.

The following flow charts should be used in sequence, where an OK from
the red HUD cases leads to blue/green HUD cases. Note the following
decompression/tissue model ‘O/C Bail-Out’ alarm states (used in the dia­gram):

No Comms — Pressure Sensor alarm is “No Comms”
Stale — Pressure Sensor alarm is “Stale”
Missed Stop — Deco Ceiling violated for more than 1min. This alarm
state latches for 24 hours.
Too Shallow — Deco Ceiling violated for < 1min
At Stop — Within 0.1 bar (deep) of the next stop
Near Stop — Within 0.3 bar (deep) of the next stop
Too Deep — Greater than 0.3 bar (deep) of the next stop

3.16

| 63

IN WATER HUD/BUD ALARMS

Red (OC Bailout) Alarms

64 |

Blue/Green Alarms

3.16

| 65

PPO2 "Bad Cell" States Are As Follows:

• Cell input timed-out

• Cell input stale

• Calibrated sensor input > 3.00 bar

• Calibrated sensor input < 0.15 bar

• Raw sensor input < 7 mV

• Cell input excluded having failed calibration

• Calibrated cell input > 0.2 bar from the other two cells (only a single cell
can be in this state)

PPO2 "Ascend" Alarm States Are:

High Span
PPO2 cell span > 0.5 bar (if 2 or 3 cells in state “OK”)

Bad Cells
1 cell in state “OK” or; no cells in state “OK” but with different high/low
alarm states or the same alarm states and no O/C bailout case

V. Low Control
If 2 or 3 cells in state “OK”, and PPO2 < -0.20 bar

V. High Control
If 2 or 3 cells in state “OK”, and PPO2 ≥ 0.70bar where; PPO2 = PPO2 –
setpoint, i.e., the difference between the average PPO2 and the setpoint.
The average PPO2 is based on the calibrated value from all cells in alarm
state “OK”.

66 |

SURFACE HUD/BUD ALARMS

Red (Do Not Dive) Alarms

3.16

| 67

PPO2 "Bad Cell" States:

• Cell input timed-out

• Cell input stale

• Calibrated sensor input > 3.00 bar

• Calibrated sensor input < 0.15 bar

• Raw sensor input < 7 mV

• Cell input excluded having failed calibration

• Calibrated cell input > 0.2 bar from the other two cells (only a single cell
can be in this state)

PPO2 "Do Not Dive" alarm states are:

No Comms
All PPO2 cell alarms are “No Comms”

Stale
Any PPO2 cell alarm is “Stale”

High Span
PPO2 cell span > 0.5 bar (if 0*, 2 or 3 cells in state “OK”)

Bad Cells
None or 1 cell in state “OK”

Very High
If 0*, 2 or 3 cells in state “OK” and average PPO2 ≥ 2.0 bar

Low
If 0*, 2 or 3 cells in state “OK” and average PPO2 < 0.17 bar
where; PPO2 = PPO2 – setpoint, i.e., the difference between the average
PPO2 and the setpoint. The average PPO2 is based on the calibrated value
from all cells in alarm state “OK”.

* Zero cells “OK” with the same high/low alarm state, in which case all three are used in the

average.

68 |

Blue/Green Alarms

3.16

| 69

PPO2 Blue/Green ‘Do Not Dive’ alarm states are:

High
If 2 or 3 cells in state “OK” and average PPO2 ≥ 1.6 bar

V. High Control
If 2 or 3 cells in state “OK”, and provide complete, and PPO2 ≥ 0.70 bar

V. Low Control
If 2 or 3 cells in state “OK”, and predive complete, and PPO2 < -0.20 bar
where; PPO2 = PPO2 – setpoint, i.e., the difference between the average
PPO2 and the setpoint. The average PPO2 is based on the calibrated value
from all cells in alarm state “OK”.

70 |

PRIMARY ELECTRONIC BAILOUT SCENARIO CHART*

3.16

Failure

Loop HUD

mode

None Usable

loop

Bad sensor Usable

loop

Bad sensor
readings

Usable

loop
(error greater
than 0.5
PPO2).

PPO2 ex­ceeds safe

Usable

loop
limits or mul­tiple sensor
errors

Wireless HP
data loss

High CO2
(>5 mb)

Very High
CO2 (>10
mb)

Usable

loop

Usable

loop

Unus-

able

loop

status

Solenoid

fire

Primary display Action Deco

Green Y System OK None. Stay on

EXPLORER

Blue/
Green

Blue/
Green

Y – Fail­safe mode

Y – Fail­safe mode

STATUS screen action
panel will show AS­CEND NOW.

STATUS screen action
panel will show AS­CEND NOW. PO2 panel

Stay on EX­PLORER and
ascend

Stay on EX­PLORER and

ascend
will be in Magenta (No
Comms)

Red Y depen-

dant on
DCP/PO

Blue/

Y STATUS screen action

Green

BAILOUT Ascend on

open circuit

2

Stay on EX­panel will show AS­CEND NOW. HP panel

PLORER and

ascend
will be in Magenta (No
Comms)

Blue/
Green

Red Y depen-

Y STATUS screen action

panel will show AS­CEND NOW.

BAILOUT Ascend on

dant on
DCP/PO

2

Stay on EX-

PLORER and

ascend

open circuit

will follow

On-board, 3
sensor driven
PO

2

Air

Air

Air

On-board, 3
sensor driven
PO

2

On-board, 3
sensor driven
PO

2

Air

* (see Alarm Tables for lower priority alarms)

| 71

3.17

Gas Reserves

DYNAMIC RESERVE

The EXPLORER monitors the high pressure (HP) contents of the on-board
gas supplies.

The EXPLORER includes two warning system for the HP contents.

1. Pressure below reserve level

2. Rate of use of gas is too high or too low indicating either a leak or that
the HP cylinder valve is turned off and gas injection is being unsuccessfully
attempted.

The gas supply reserve level is dynamically adjusted based on depth
(because ascent times vary with depth) and assumes a stressed breathing
rate of 20 l/min on open circuit bailout using the on-board cylinder. If the
system sees this reserve limit approaching, it will warn the diver to ascend.

BAILOUT TO OPEN CIRCUIT

Should the operation of the EXPLORER generate an emergency alarm (red
HUD LED and vibrating HUD) then the diver must bailout to open circuit
on either the in-board supply (above 18 m/60 ft) or the off-board supply
(below 18 m/60 ft).

NOTE: Decompression calculations for the ascent profile will
assume air as a breathing gas to provide additional safety
during a bailout ascent.

72 |

MOD (Maximum Operating Depth)

The EXPLORER will warn on the main display if the maximum operating
depth of the unit is exceeded. This MOD is based on three things:

1. A maximum depth of 40 m/130 ft

2. A maximum depth such that the gas attached to the unit (as measured)
cannot result in a PPO2 exceeding 1.6bar.

3. When a maximum PPO2 of 1.6 bar is reached

The EXPLORER will not freeze the user out of operation if these depths
are exceeded. However, the system and diver are operating beyond the
normal recommended conditions and therefore these limits should never
be routinely exceeded.

WARNING: Exceeding these limits is not condoned by the man-

!

ufacturer and is not a safe diving practice and must be avoided.
If an MOD alarm is seen then you should ascend immediately to
a depth where the alarm is not displayed. This depth reduction
should be at least 6 m/20 ft but could be more if the MOD has
been exceeded by a large amount.

3.18

| 73

3.19

Decompression contingency

The EXPLORER is designed for recreational diving without decompression.
All dives however require safety decompression stops to be conducted
(consult your training agency for information).

If you accidentally stray into decompression the system will generate a
green/blue HUD alarm, the decompression stop, and stop time will be
displayed on the STATUS screen. This feature is designed for contingency
purposes only.

!

DANGER: The EXPLORER is not designed for use with gases
other than Nitrox.

WARNING: Decompression diving signicantly increases the

!

risk of decompression illness.

Various alarms will be generated if elements of decompression are vio­lated. Please see the Deco States Table below and the EXPLORER flow
charts for further detail.

DECO STATES

State Reason HUD Color

Code

Missed Stop Missed deco stop Blue/Green MISSED STOP!

Too Shallow Deco Ceiling violated

for < 1 min

At Stop Within 1 m/3.3 ft below

the next stop

Near Stop Within 3 m/10 ft

of the next stop

Too Deep >3 m/10 ft below ceiling Blue/Green DECO!

NOTE: When you have decompression stops to complete (or if
any alarm is showing) the STATUS display will remain on (and
not automatically time out).

Blue/Green DECO!

Blue/Green AT STOP

Blue/Green NEAR STOP

Status Screen

Display

USE TABLES

DESCEND NOW

WAIT
x MINS

ASCEND TO
x M (FT)

ASCEND TO
x M (FT)

74 |

Internet Reprogramming

The EXPLORER can be automatically reprogrammed and upgraded with
new software downloads from the Internet. The PC Link option enables use
of this feature. Contact the manufacturer web site or your dealer for more
information.

Some updates will be available for a fee. Other updates will be free.

To check if you’re EXPLORER has any available updates and to obtain the
reprogramming software then please go to http://hollis.com/support.asp.

DANGER: After new software is installed you MUST recalibrate

!

the oxygen and CO2 sensors.

3.20

| 75

Getting Ready To Dive

gear prep

WEIGHTING

As the counterlungs inflate, the diver may experience movement in the
EXPLORER. This is minimized by tightening the harness or adding trim
weights to the pocket available on the top of the case. A weight of up to
2-3 kg/4.4-6.6lbs can be used.

If the EXPLORER is allowed to move on the divers back, a change in
breathing resistance may be noted. With the Explorer’s back mounted
counterlungs it is important that the Explorer is as close to the diver’s back
as possible.

Your instructor will teach you how to weight yourself correctly.

WARNING: Over-weighting is dangerous. With an empty BCD,

!

no additional bailout cylinder and 50 bar/735 PSI in the main
cylinder you should be able to begin slowly to submerge in a
controlled fashion by exhaling slightly (too much and the ADV
will add gas).

WARNING: It is important to perform weight checks in conned

!

shallow water with at least 50 bar/735 psi bailout gas prior to
any open water diving.

HARNESS/BCD POSITIONING

When adjusting the harness try and imagine that the center of the count­er-lungs should be within ± 100 mm/4 inches of the tip of your sternum
to give an optimum breathing performance. While the BCD/harness must
be comfortable it should not be loose. The harness will sit differently on
land compared to when you are in the water.

76 |

OCTOPUS, BAILOUT, & CYLINDER CONFIGURATIONS

While the exact gas requirements for any type of diving are a matter of per­sonal choice and predicted by specific level of EXPLORER certification and
training agency, it is vital that a breathable open circuit bailout is carried
at all times for all depths of the dive, of sufficient volume to allow a safe
ascent to the surface with a stressed breathing rate.

NOTE: Certain training agencies may required additional gas
supplies for diving in ‘mixed teams’ (open circuit/closed cir­cuit). Please check with your agency for details.

!

DANGER: It is vital that a breathable open circuit bailout is car-

ried at all times for all depths of the dive, of sufcient volume

to allow for a safe ascent to the surface at a stressed breathing
rate.

!

DANGER: For deep/long duration dives the on-board gas sup­ply should only be treated as a short-term gas supply, used for
a limited period until the off-board bailout gas can be accessed.

WARNING: In depths shallower than 18 m/60 ft you must be

!

able to provide gas to another diver (buddy). This will require
the use of an additional second stage octo attached to your EX-

PLORER rst stage if you are not carrying an external bailout

cylinder.

4.1

NOTE: The BOV is connected to the on-board gas supply.
Dives shallower than 18 m/60 ft dives can be conducted using
only this available gas as a bailout providing that the gas en­durance alarms are not exceeded on the unit.

NOTE: Certain training agencies may required additional gas
supplies for diving in ‘mixed teams’ (open circuit/closed cir­cuit). Please check with your agency for details.

| 77

The following is offered as a guide when configuring the EXPLORER for
a range of diving conditions. This must be used in conjunction with the
recommendations from your Hollis approved training agency.

Depth On-board Gas Off-board Gas

Less than 18m/60ft 5l @ 200 bar/2940 psi

Not required
(1000 l/40 cuft). Nitrox
32 to 40%

>19m/63ft to
40m/130ft

5l @ 200 bar/2940 psi
(1000 l/40 cuft). Nitrox
32 to 40%

Air to 40% nitrox of

sufficient volume for an

ascent from depth with

a 150 l/5.3 cuft reserve

at the surface after an

open circuit ascent.

Bailout gas volumes should be calculated based on the depth of the dive
and the ascent gas requirements. Cylinders can be positioned on D-ring
attachment points on the harness or optional EXPLORER BCD.

Your Instructor and Training Agency will detail how to calculate for suffi­cient bailout gas volumes.

COUNTERLUNG VOLUME

The volume of gas in the counterlungs will affect the ‘breathing feel’ of
the unit. Too little gas will make inhaling difficult and too much will make
exhaling difficult. All retreaters have optimal positions in the water where
they have a better or worse breathing feel due the hydrostatic effects of the
counterlung position and the breathable volume within the counter-lungs.

It is important to balance the volume in the breathing loop so that exces­sive inhale or exhale pressure is not experienced.

Under certain situations the EXPLORER will vent during the exhaled breath.
This will result in a drop in oxygen levels and more gas addition by the
system.

It is possible to balance the loop to an extent by venting a small amount
through your nose, particularly on ascents if the need arises.

78 |

ADJUSTING THE BREATHING ‘FEEL’

The breathing ‘feel’ of EXPLORER is partially controlled by the LCV. Having
removed the case cover this can be seen underneath the Canister. This
is an adjustable valve (over a small range). Oriented as shown, Moving
the valve to the left vents more easily and to the right it vents at a slightly
elevated pressure (Fig. 4.1).

The LCV is a hydrostatically balanced valve, this means that in any swim
position it releases gas from counterlungs at approximately the same pres­sure and rate. In addition it is a water drain device and it is connected to
the exhale counterlung via a water drain tube such that as water enters the
counterlung (condensed exhaled breath) then it moves through the tube
and out of the LCV regularly throughout the dive.

THE AUTOMATIC DILUENT VALVE

The EXPLORER also has an automatic diluent addition valve (ADV), which
compensates for loss of gas volume. To activate the ADV either descend
or exhale through your nose and breathe in. The ADV is designed to help
maintain a breathable lung volume in conjunction with the LCV.

The ADV on the Explorer is a simple tilt lever system that in the relaxed
position (no gas applied) will remain open. It seals when gas is applied.

4.1

Fig. 4.1

If moisture is present in the system and extreme freezing temperatures are
experienced that are able to form ice within the rebreather this valve could
freeze in the open position. Freezing of ADV’s is a common failure mode
in most rebreathers. The EXPLORER design assumes this and provides an
additional link to the Pre-dive alarm sequence to warn of such a failure.

If the valve is frozen open then gas will freely flow into the circuit. This will
give a ‘HIGH HP’ usage alarm and the unit will fail its Pre-dive sequence.
This is the correct failure mode for this device.

If the system had been pressurized and then it froze and hence the valve
failed closed, again pre-dive will fail momentarily until counterlung collapse
removes the icing as the lever activates, then pre-dive will pass unless
there is a leak due to icing then the pre-dive will again fail (high gas flow
alarm).

| 79

This system was developed because in use no units are completely free
from moisture, and ADV free flows, due to icing, regularly occur though
there has not been an alarm for it.

80 |

PRE-DIVE SETUP

Having assembled and tested the unit upon receipt, it is still critical that all
pre-dive tests are conducted prior to diving.

The EXPLORER is equipped with a set of pre-dive checks that are built into
the electronics prompting the diver to test certain aspects of the unit prior
to diving. Additionally, there are several manual tasks that should be com­pleted prior to this final system check. These checks automatically start
once you turn the unit on. A complete flow chart of all the screen layouts
can be found on the enclosed CD and in the rear of this manual.

TURN ON SYSTEMS

The EXPLORER can be fully activated in three separate ways:

1. By button push

2. By breathing (breath detection as a low PPO2 of 0.17 is reached)

3. At depth (>1.15 bar absolute pressure or about 5 ft/1.5 m)

DANGER: The batteries must be charged for the automatic sys-

!

tems to work. If the batteries are not charged the unit will not
turn on and not support life.

To turn on EXPLORER simply press both buttons on the handset and
hold for 3 seconds. After which, the Hollis splash screen and then the
training acknowledgement screen (Fig. 4.2) will appear.

4.2

Fig. 4.2

!

DANGER: It important that you have read this manual and are
properly trained in order to complete the Pre-dive sequence
and dive EXPLORER safely. If you have not undertaken these
steps yet, do not proceed any farther.

By selecting CONFIRM the Pre-dive sequence starts and you will be
prompted through the sequence.

At the end of a successful Pre-dive sequence you will see the check
resources screen (Fig. 4.3).

At this point you should cycle through the screens by pressing the
left or right button to check that all resourcesare adequate to com­plete the dive. After a few seconds the display will time-out to the Dive
screen (Fig. 4.4).

Fig. 4.3

Fig. 4.4

| 81

EMERGENCY START-UP SYSTEM (ESS)

Should you have no option other than to enter the water immediately,
EXPLORER will activate the display and show all pertinent alarms in the
STATUS screen. It is vital that you correct anything in error immediately
before continuing to dive.

If you enter the water without completing the relevant Pre-dive checks
and ESS mode is activated, you will be given an O/C bailout alarm (red
HUD) warning you to return to the surface immediately to complete the
Pre-dive checks. After 1 minute underwater (if nothing else is alarming)
the bailout alarm will stop.

!

DANGER: The ESS should never be used as a routine diving
start-up system. A full Pre-dive check MUST always be con­ducted to ensure safe operation. The ESS is designed ONLY as
a safe guard. If you have not completed pre-dive checks, abort
the dive and perform a proper pre-dive on the surface.

Fig. 4.5

LESS THAN 2 HOUR PRE-DIVE SEQUENCE

If you have completed a Pre-dive Sequence within the last 2 hours, then
upon reactivating the unit (assuming there is nothing wrong with the sys­tem) it will display the Hollis splash screen followed by two screens (Fig.

4.5, 4.6). It will then allow you to dive immediately.

TURNING OFF

The EXPLORER cannot inadvertently turn off while submerged. Although
while at the surface, if no button pushes are detected within 15 minutes it
will automatically turn off to save power (Fig. 4.7).

To manually turn off EXPLORER then select the Menu option and do a
long press of the left button - OFF (Fig. 4.8).

Fig. 4.6

Fig. 4.7

Fig. 4.8

82 |

FILLING THE GAS SUPPLY CYLINDERS

The nitrox cylinder has a maximum fill pressure. This is stamped on the
cylinder and must be checked before filling. Refer to regional limitations for
maximum fill pressures. Install the nitrox cylinder into the case and tighten
the cam band. Now install the regulator DIN connection.

DANGER: Although the EXPLORER will analyze its own gas

!

supply it is still important that you always analyze your gas
prior to use.

WARNING: If you suspect that the cylinders have become con-

!

taminated with salt, water or other contaminants then you must
get the cylinder inspected and cleaned as appropriate.

GAS ENDURANCE

Gas endurance is defined by the Dive Control Parameter (DCP) setting.

With the cylinder pressurized to 200 bar/2940psi and assuming a usable
gas pressure of the working pressure (minus the regulator interstate pres­sure of 11 bar/161psi) this equates to 189 bar/2779psi available.

4.2

Assuming a DCP setting of 50% and a worst case FO2 of 32%. The EX­PLORER gas supply will last a maximum of 189 minutes based on normal
swimming work rates.

The EXPLORER will continuously update gas minutes remaining through­out the dive for any DCP setting and work rate.

DANGER: High pressure gas cylinders (especially nitrox cylin-

!

ders) must have their cylinder valves opened slowly to avoid
risk of injury.

This duration is also dependent on how much loop venting, mask clearing,
BCD/drysuit inflation occurs.

NOTE: Cylinder valves for use with the EXPLORER must be

certied in accordance with EN12021 for use in Europe.

| 83

THE ABSORBENT FILTER

The unit has been tested under CE requirements for CO2 absorbent filter
duration. The weight of absorbent in the filter is approximately 1.5kg/3.3lbs.
Tests were conducted with Molecular Products 797 Grade CO2 Absorbent.

WARNING: Using any other absorbent will change and possibly

!

reduce the Canister duration and could lead to injury or even
death.

CANISTER DURATION

At 40m/130ft of depth, with Nitrox 32% as a diluent at 4 °C/39 °F water tem­perature with a CO2 injection rate of 1.6 l/min and a ventilation (breathing
rate) of 40 l/min and a 1.5 kg/3.3 lbs absorbent load of a Hollis Approved
absorbent (See Unit Specification), the unit will last 40 minutes at 40 m/130
ft as an extreme test (Ref EN14143: 2003).

This duration changes significantly with higher temperatures and low­er work rates

continued

84 |

Below is a table of endurance versus depth and changing workloads with
temperature.

MINUTES TO 5MB CO2 REFERENCE

4.2

Depth Total dive

time

40 m/130 ft 37 mins 40 l/min Hard swim-

40 m/130 ft 120 minutes

+reserve
capacity

40 m/130 ft 88 mins 40 l/min Hard swim-

DANGER: Ventilation rates up to 40 l/min are referenced as

!

"Normal swimming" and rates of 40 l/min and above are refer-

enced as ‘Hard swimming’. Under strenuous conditions howev­er consumption rates may be signicantly higher. Regardless

of conditions or readings on the computer, the scrubber should
NEVER be used for more than 2 hours.

WARNING: These tests were conducted using Hollis approved

!

absorbent grade and durations can only be duplicated using
this grade. DO NOT use any other type of absorbent with the
EXPLORER. Safety data on absorbent products can be found
at: http://www.molecularproducts.co.uk

Ventilation

Work rate Water temp

rate

ming

22.5 l/min Normal
swimming

ming

4° C/39° F

15° C/59° F

15° C/59° F

Tests conclude that depth (gas density), temperature, and CO2 generation
all massively affect absorbent duration. The EXPLORER employs a highly
efficient axial canister design which not only offers greatly extended dura­tions when compared to other designs employing a similar absorbent load,
but it is less affected by the commonly experienced high loss of efficiency
associated with increased depth.

| 85

FILLING STEPS – PROPACK VERSION ONLY

!

DANGER: DO NOT perform this action unless you are certied

to do so.

1. Remove the Filter from the Canister. Inspect the quad ring for cleanli­ness/damage and clean/replace with a small amount of grease (Fig. 4.9).

2. Unscrew the yellow top nut and canister lid and inspect the meshes for
damage.

3. Remove any excess absorbent stains from the canister components
with warm, soapy water and then rinse in fresh water. Then allow it to dry.

4. Fill the canister in a well-ventilated environment. Raise the absorbent
barrel at least 200mm (8 inches) above the canister to allow dust to blow
away as you fill. Fill to the top of the canister, making sure absorbent is at
an even depth across the canister.

5. Pack the absorbent by tapping the sides for at least 1 minute.

6. Fill to the top again.

7. Pack the absorbent by tapping the sides for at least 1 minute

8. Refill with Absorbent to the top. Tap down as required until you can fit
the lid. Refit the lid and the spring (under the yellow nut).

9. Screw down the top nut.

10. Wipe any dust from inside the canister.

11. Look into the Canister head and run your finger around the sealing
face for the quad-ring removing any debris.

12. Insert the filled Filter into the Canister.

13. Refit the Right Hand end cap.

14. Dispose of old absorbent as normal household waste. Do not leave it
lying around for animals to ingest.

Fig. 4.9

Filling instructions are also found on the side of the canister tube.

FILLING STEPS – PRE-PACKED VERSION ONLY

1. Remove the Filter from it sealed packaging.

2. Inspect the quad ring for cleanliness/damage

3. Apply a small amount of grease to the quad ring.

4. Wipe any dust from inside the canister.

5. Install the filter.

6. Refit the Right Hand end cap.

7. Dispose of old absorbent filter as normal household waste. Do not leave
it lying around for animals to ingest.

86 |

POST DIVE

During a diving sequence, it is important that a small amount of daily main­tenance is undertaken. These fall into 5 categories:

1. Care of oxygen and CO2 sensors

2. Loop cleaning

3. Recharging

4. Cylinder filling

5. Absorbent changing

6. BCD

CARE OF OXYGEN AND CO2 SENSORS

The Sensor Module (SM) is easily removed from the unit by removing the
Life Support System Module (LSS) and pulling the SM out. The SM carries
the three oxygen sensors and the CO2 sensor.

Post dive the CO2 filter (yellow cap) sponge should be replaced as de­tailed.

At the end of a days’ diving the complete SM should be removed (and the
LSS cap refitted) and kept in a dry (low humidity) and ambient tempera­ture environment. The CO2 filter cap should be removed for the non-diving
period.

4.2

LOOP CLEANING

After a dive the hoses should be removed and fresh water should be
flushed through the complete assembly and be allowed to drain out. To
remove excess water, push the hose corrugations together (like using a
concertina) to squeeze the water out.

Disinfect the unit as per the ‘Explorer Rebreather Maintenance Chart’,
PART 7 Section 4.

RECHARGING

Please see "Batteries" PART 1 section 2.

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CYLINDER FILLING

All dives must start with a full cylinder. All gas must be analyzed prior to
use.

ABSORBENT CHANGING

Absorbent must be changed in accordance with the section in the manual
titled ‘The Absorbent Filter’.

BCD

Drain any water from the BCD. Re-inflate and the operate dump valves and
the inflator to confirm everything is OK.

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COMPLETING PRE-DIVE CHECKS

PURPOSE

These tests are designed to:

1. Check that all functions of the EXPLORER have a high likelihood of oper­ating correctly

2. Detect assembly errors

3. Detect breathing loop errors

4.Advise the user of system measurements that are outside correct
operating parameters including:

a. High Pressure readings too low
b. High Pressure readings dropping too quickly – possible leaks
c. Battery Levels
d. PPO2 partial pressure of oxygen in the breathing loop
e. Calibration of PPO2/CO2 sensors performed correctly
f. Ensure the CO2 absorbent is functioning correctly, and the filter is
inserted correctly and is sealed

THE COMPLETE (PASS MODE) PRE-DIVE SEQUENCE

The complete sequence is detailed on the following page. This sequence
assumes all tests pass OK and no Pre-dive has been conducted within one
hour. The full screen chart is available on the CD enclosed with the prod­uct. An APP for any Android device is available at http://hollis.com/support.
asp and on the enclosed CD with your EXPLORER.

4.3

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Title

subtitle

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From the dive screen, each resource must then be checked (Fig. 4.10).
Once you have checked each resource the STATUS display will show
SYSTEM OK.

DIVING WITHIN 2 HOURS OF A SUCCESSFUL PRE-DIVE SEQUENCE

If you start a dive within two hours of a successful Pre-dive being conduct­ed then EXPLORER will display the following Startup screen (Fig. 4.11).
Now you can simply select DIVE or go through the Pre-dive sequence
again by selecting PREDIVE.

4.3

Fig. 4.10

Fig. 4.11

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User Fault Finding & Testing

PRE-DIVE PRIMARY ERROR MESSAGES & THEIR MEANINGS

Message Meaning

The batteries in the EXPLORER
must be charged prior to diving.

CO2 sensor is unable to calibrate
and must be replaced or removed
(the 5 minute pre-breather system
will be activated).

O2 sensor(s) unable to calibrate
and must be replaced and/or their
connectors cleaned.

O2 sensor(s) unable to calibrate or
failed LSS/Sensor Module.
Recharge unit and try again. Return
to dealer if problem persists.

Negative test failed. Ensure Cyl­inder is attached. Ensure Mouth­piece is fully in OC mode. Fill loop
until vent valves exhausts then
attempt negative test again.

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Message Meaning

Low HP gas in dive cylinder.

If HP reduces by >50bar/735 psi
or does not reduce by at least
5bar/73.5 psi.

Make sure cylinder valve is fully
open.
Check cylinder size is correct in
DEFAULT GAS Menu. Do not use
unlisted cylinders. Submerge unit
and look for LP/HP leaks, BC infla­tor failures etc.

4.4

Wireless HP sender battery is low.

Analyzed gas is not what is
expected by the DEFAULT GAS
setting.

Analyze gas and check setting.

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Message Meaning

The LCV and OPV are not vent­ing at the correct pressure. Flush
valves with fresh water and repeat
test. If the problem persists return
the unit to your dealer.

You have stopped breathing while
conducting a pre-breathe se­quence.
Repeat the test. If the error per­sists return the unit to your dealer.

If the Predive sequence is com­pleted, the STATUS window is
active, and you see the above
alarm, then HP usage is greater
than 1bar/min – 14.7 psi/min.

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This could indicate a leak in the
HP or LP circuit (internal pipe­work), BC or BOV. Submerge to
locate the leak.