Become a Safe and Efficient Dive Explorer

A-Z innovative guide to the diving techniques used by the most succesful Dive Explorers and Researchers worldwide.
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  • Lectures 115
  • Length 11 hours
  • Skill Level All Levels
  • Languages English
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About This Course

Published 3/2013 English

Course Description

A torough Foundation for Divers seeking valuable knowledge in which to start developing a solid base towards Safe and Efficient Exploration of new dive sites, wrecks, mines and even untravelled cave passages.

Application of Rebreather technology and multiple DPV's can easily result in extreme exposures that will take the Dive Explorer beyond traditional diving industry limits.

How to be prepare to endure multiple hours dives at depths beyond 100mt / 330ft while breathing multiple Breathing Mixes of Nitrox and Trimix while exploring dive areas, possibly no man ever been before, is what Dive Explorer Training is all about.

This course should be paired with in-water practice by an experience Instructor, actually is a perfect tool to have when planning to take any Technical Diving Course, but also invaluable aid is thru mentorship in actual Exploration Projects.

This is the IDREO Explorer Diver Manual for all IDREO Training levels.


What are the requirements?

  • Online Course - NONE

What am I going to get from this course?

  • Academic Foundation for Experience Divers
  • Update Diving & Exploration Techniques
  • Deep Diving Techniques
  • Single & Multiple DPV Diving
  • Rebreather Technology Operation (pSCR, CCR, ApSCR, Deco rebreathers)
  • Cave & Overhead Diving Techniques
  • Long Range Penetration
  • EXtreme Exposure Planning & Management

Who is the target audience?

  • Cave/Rebreather/Tech/DPV/Stage/Survey Divers
  • All Agencies Diving Students
  • Dive Explorers
  • Dive Researchers

What you get with this course?

Not for you? No problem.
30 day money back guarantee.

Forever yours.
Lifetime access.

Learn on the go.
Desktop, iOS and Android.

Get rewarded.
Certificate of completion.


Section 1: About this Course

    In this IDREO course you can create a solid foundation to become a better diver, understand the requirements and skills need to pratice in order to become a Safe and Efficient Dive Explorer.

    Expect videos, voiceover presentations, documents, quiz and written examinations in the following Topics:

    General Diving Knowledge

Equipment Configuration (OC/RB Back & sidemount )

Dive Planning

Deep Diving


Trimix Decompression

Extreme Exposures

Rebreather Diving




Cave Diving

Basic Cave Diving

Complex Navigation

Restriction Negotiation

DPV Diving

Exploration Considerations

  • IDREO was found as an International Organization to link worldwide explorers and share experience and knowledge to reach further where no Man been before, for more information visit

    As a way to increase safety among explorer IDREO promotes Exploration Mentoring thru a seminar in actual Exploration and Research Projects, however as many divers wishing to participate where lacking training and information.
    Furthermore one of IDREO research projects is the Accident Analysis Project, AAP, found in 2011 increase in cave diving fatalities, to more than 10 times the yearly average, and divers involved where mostly under exploration activities the IDREO training was the response to promote safer and more efficent Exploration.

Section 2: Introduction to IDREO Explorer Training

Welcome to IDREO !

Nick Toussaint talks about the motivations of founding IDREO, Accident Analysis Project, IDREO Training and finally how to promote Safer & Efficient Exploration.

Nick Toussaint is an experienced Diver and worldwide recognized Cave Explorer. He is probably one of the most accomplished and a worldwide renown expertise as a Cave Instructor to all levels based on 18yrs experience teaching worldwide with a perfect ZERO accident record.

Nick Toussaint still trains Divers to all levels on all major cave destinations worldwide yearly, and is the main leader on the IDREOseminars. He has shared his passion and knowledge about cave diving at conferences in various diving shows, articles and even sport TV shows around the world and as well is an active participant in equipment development and testing specifically for cave diving. He started Cave Diving in the Yucatan Peninsula in Mexico, the most wanted location for recreational cave diving
and got NACD, TDI and NSS-CDS certified in the mid 90's and has taken Cave Instructor training with IDREO , GUE, IANTD, TDI, CMAS, UTD, NAUI, PADI, & SDI, while creating outline and diver programs at various levels for many of them.In 2008 received from NSS-CDS the Sheck Exley Award, with International endorsement, which is given for accomplishing 1000 non training cave dives in at least 5 countries.

Nick Toussaint has cave dived in 12 countries, and just about every cave system in Mexico. Starting in Quintana Roo, Merida in the Yucatan Peninsula but also In the North state of Tamaulipas; been privileged to explore many of them. Also very familiar with most popular cave diving sites in Florida and Europe, including France, Italian Alps/islands, Switzterland, Scandinavian mines, as well as various Australasia cave diving destinations.

You can contact Nick Toussaint by email

IDREO Seminars were born as a response to the increase of cave diving fatalities mostly under exploration like activities in 2011 as noted by the IDREO Accident Analysis Project .

Seminars are free of cost as the idea is to mentor divers wishing to participate in exploration and eventually create their own projects. The seminar participants need to be solid and experience divers with certification in Mixed Gas Diving, Rebreather, DPV and Cave Diving.

Due to divers needing to fill holes in previous training, updating diving techniques or still under diver formation step IDREO decide to provide comprehensible and to the point IDREO Diver Training program.
10 pages

Print this file and take it to your training session, in order to record the IDREO Training in detail


The Workbooks are printable pages with the key information required to assimilate in a given course, they have proof a valuble tool as reference material after training but also asssit the trainee to have a dedicated space to write notes and/or questions, the idea is that you use it while going thru this classroom and therefore bring it full to the actual training, at the end you should also attach the answer exam for your instructor to review.

The Explorer Seminar need all Four current Workbooks:

1. Deep Explorer

2. Rebreather Explorer

3. Cave Explorer

4. DPV Explorer

The exams are a very valuable tool to make sure you know the most important information about each diving topic. There is a 4th Exam for DPV diving.

NOTE: Workbooks on different languages on each section.

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Section 3: Basic Diving Knowledge

This Basic Diving Physics video is been shared by the Dive Explorer Foundation, DEF.

In the mid 1600's, Robert Boyle studied the relationship between the pressure P and the volume V of a confined gas held at a constant temperature. Boyle observed that the product of the pressure and volume are observed to be nearly constant. The product of pressure and volume is exactly a constant for an ideal gas.

p * V = constant

A solid Dive Plan is paramount in diver safety, but also critical in achieving dive goals.
The Dive Plan simple touches all the limits the team has for a given dive and
also underlines a "LIMIT LINE" when turning around back to surface should be happening.
Remember in a good plan limitations are hardly ever reach simultaneously,
so this mean you may have to call the dive on gas, time, depth or anything else,
so don't expect all Dive Plan limitations to happen together.
Divers should consider calling the dive anytime reaching ANY of the giving limitations.

When discussing Bailout we are talking as the back up plan to get out of trouble, in diving the worst possible scenario is sharing gas from the furthest point of penetration.

Proper Bailout is enough quantity of gas to make a OOG scenario work from furthest penetration point back to the surface, divers require to be able to make acurate estimations of gas need, plan adequate redundancy for further failures and be able to handle the bailout carrying options such as double tanks, stages bottles, deco bottles, multiple scooters and DPV's maybe be need to make the Bailout feasible.

Variations of Bailout are Minimim Reserve and Rock Bottom with basically same deifinition but applicable to specific situations such as a direct ascent to surface vs tunnel trael prior the ascent.

Indentify the Bailout calculation criteria and the options divers have in order to provide this important safety feature to all planned Dives.


NDL stand for NO DECOMPRESSION LIMITS, but thruth is there is not such a thing as we relay on ascent speed, 10 MT / 30 FT per minute or if you wish 20 second stops each 3MT / 10 FT so to explain.

NDSL may be more accurate and stands for No Decompression Stop Limits, which are the minimum times a diver can stay underwater at a given depth before having to perform actual decompression stops before surfacing, so pretty much a direct ascent to surface, as long as respecting a defined minimum ascent speed usually 10mt/30ft per minute.

NDSL Times varies with depth and therefore flexibility in figuring out the times is key in manging efficient and safe exposures.

IDREO offers an easy and accurate rule to "on the fly" been able to figure your NDSL, while at the same time build up the skill need to manage the flexibility exploration diving will require. Notice the plan dive is not always possible to know ahead of time or can change dramatically without expecting it while underwater.

In short 120 rule.


Nitrox diving requires same skill than diving air, however proper understanding of risk and diving procedures is the main focus of any Nitrox course.

Advantages of using Oxygen enriched diving mixes are extended bottom times without NSDL.

In this lecture you will understand the reasoning and the strategy for diving Nitrox.

12 pages

Standardized Hand Signals make extremely fast and accurate comunication while underwater, without having to Stop and write down what is going on in your wetnotes. Wetnotes are mostly used for Data gathering.

Repetitive task are best served by a specific set of Hand Signals, notice gloves or to slow or fast movements make create complications when aplying Hand Signals for communication.

Basic Dive Signals


Expert Divers use lights not only to look around but for efficient communication.

Light communications
is both Active & Passive.

In this lecture we review Light Communications and Light Signals the goal is to understand them better to take the most advantage from using them.


The Diving Bottles choices available for carrying efficiently the different gas need during a dive are very much define by material and size but also a keypoint is the configuration options.


All divers must be reasonably educated about Basic Diving Equipment function and operation as well as periodical maintenance.

The Basic Diving Equipment is Open Circuit and is a redundant (back up) version of the traditional Single Tank Diving, the extra components greatly increase diver task loading if not properly configured.

We should strive to bring only what we need for the dive, making sure we don't leave nothing we need behind but more important we are not dragging stuuf we don't need. Owning a piece of Basic Diving Equipment does not automatically means we have to take it.


DEF OW Sidemount configuration is solid foundation to explore the underwater realm, it's minimalistic approach allows the diver to efficently move underwater due to minimum drag.

This is the DEF Scuba Explorer main recommended configuration for Non Divers.

The DEF OW Sidemount configuration is based in a back plate with a solid one piece webbing strap.


Diving Basic applied to basic side mount diving, sponsored by White Arrow


Divers can benefit of a reliable and durable Lighting System, as besides providing ilumination which is mandatory in the overhead is a great tool to get team attention and stay together thru passive comunication.

A Light Canister does provide enough burntime for making an extensive dive,
with expectancy usually no less than 1 hr burntime and as long as 15 hr,
minding repetitive dives and/or bailout plans times.

In any case the Canister Light should stay ON for the planned dive duration,
in fact it's duration maybe as well be a limitation in order to call the dive;
for example if you are going in and out a cave need to use half of the expected burntime going in,
just to make sure you won't run out of batteries upon exit.

The canister light are usually of two core parts the Canister itself and the light Head.
Both components are attach by a cable.
Dealling witht this cable could be a bit of out of the ordinary and natural at the beggining but quickly becomes part of the diver with a little practice and some tips to remember when using it,
even in emergecy situations such as sharing gas or failures !

Advice at properly dealing with canister light cable.

  • Use Goodman handle
  • Cable most be the "right" length
  • Understand each arm "needs"
Basic Mask Removal and replacement with proper trim and buoyancy control,
is agreat way to practice buoyancy and trim control, so this is the first skill to master !

You need to not hold your gas for long and remain cal thru the process, divers that are not confortable at Mask Removal underwater, still need to wait a bit longer before venturing in technical diving, rebreather diving or cave diving.

Smart divers do carry a spare mask inside the suit pocket, and getting to it is also a great skill to master.
What is a Frog Kick ?

In this video you can see an average diver skill at using a Frog Kick as propultion technique while is not yet perfect is the minimum level you should have before aplying for IDREO training.

To make this Frog Kick perfect diver knees will remain at same height than torso, therfore providng less drag in the glide portion of kick.

In fact Frog Kick is NOT a continuos movement more of a trust and glide combination, this prpopultion techinque done properly can be done by hours without changing diver comsumption rate even with doubles and a stage/deco bottle.

The Frog Kick vortex goes behind the diver, therefore avoiding stirring the bottom sediments.

Performing a Valve Check is a fast an organized way to verify all valves are open, the valves should be moving to be open, never jam open the valves, one you turn the valve on go back half a turn.


Procedure for Regulator Exchange, switching from Primary Regulator to Back Up Regulator.


When in need to share gas with a dive partner is a lot easier and efficient to do so while each member has absolute control of personal buoyancy and trim, as other way need to complicatedly operate as one unit, which can result catastrophic if letting go of each other during ascents.

As well wehn in need to travel to tight restricted tunnels of passage can proof cahllenging and even impossible unless the team is equipped with a Long Hose in the main regulator.

The Long Hose typically is been 7ft, 2 mt long as standrd and is quite easy to handle it underwater if wrap around the diver torso and behind the neck, securing under the battery canister of the Light or electrical heating device.

When deploying the Long Hose switch to back up reg and offer what is the correct mix and working regulator out of your mouth.
Paramount in safety when diving with multiple breathing mixes in different bottles.

Low Visibility may required team to modify formation and even in worst scenarios use a line for efficient navigation even in the case of a momentary zero visibility event or exit.

Experience Low Visibility and understand the proper team formation in single file, when on the line due zero viz touch contact must be performed.

Is pointless to start dives in zero visibility.

This how you are supposed to use your Wing Dump Valve !

So using the Wing Dump Valve promotes the right trim amd more drag on ascent so even more buoyancy control, when compare to standing up to use the corrugated hose.

Divers having problems operating dumpvalves in wings maybe more confortable using 360° degree wings and from those move into the horse shoe type, that allow alittle better weight distribution when loaded of gear using DPV's.

So keep practice going and reach for that Wing Dump Valve cord, once you get use to it even thick gloves is a non issue reaching for the Wing Dump Valve and using it, but is true that in cold water and/or salt water you may not even need to use the wing at all !

While maintaining the trim and buoyancy reach for the Suit Pocket and open it choose what you need and then close it again, the proper operation of Suit Pockets greatly reduces or completely eliminates the chances of loosing your spare gear during the dive, reducing drag an possible entanglements points.

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Section 4: Deep Diving Knowledge
22 pages

Deep Explorer Workbook to print and use as part of IDREO Deep Explorer classes.

This Deep Explorer Workbook is design to match the information need during participation of a IDREO Deep Explorer Class, we have several languages and strive to list the most updated version.

20 pages

IDREO Oxygen Toxicity E-Book is acompilation of the latest information known on Oxygen Toxcity, Hyperoxia as well as Hipoxia.

Is very important to understand the industry standrds before attempting to manipulate, transform or adapt it to specific or special needs.

The history of research as well as the conventinal monitoring, calculation and strategy to manage Oxygen Toxicity risk are part of the topics each diver must review


8 pages
This ebook contains general information in the Diving Gases available for divers.

Thru the chapters the Diving Gases are reviewed, described and also some applications suggested, which is important to provide the diver with a general background in which to build a proceudres strategy.

In dowloadable section o fthis E-book you can study the Diving Gases in Mixes as individual topics, such as NITROX, TRIMIX, ARGOX, HIDROX, HIDRELIOX as well as a quick reference gas chart.

IDREO Standard Mixes are discussed in the following lecture IDREO Standard Mixes.

One of the keypoints in making a succesful and flexible Decompression strategy is to repeat use between a few gases, as in Standard Mixes for standard applications such as Bottom Mixes and Deco Mixes.

The Standard Mixes should respect parameters reflecting the risk the diver and team agree to cope with, specially in O2 parameters and Narcosis. However is no secret nowdays that "Deep Air " risk is not only Nitrogen Narcosis the "real danger" of breathing Air at depth below 30-40 mts is Oxygen Toxicity the real enemy, which opposed to Narcosis will make diver convulse and loose conciousness. The Oxygen limits applied by IDREO are min .40 PO2 in any RB operation, perferably below .7 and Max 1.0 PO2 at any bottom mix portion of planned dive, 1.2 PO2 on below 90mt deco or short deep exposures, PO2 1.4 on "Deep Deco" or brief NDL dives, 1.6 in 21-6mt deco stops and PO2 2ata inside habitats.

The Explorer don't have necesity or willingness to high level of Narcosis while driving DPV's,  monitoring Rebreather's breathing mixes & gases, navigating thru overhead tunnels, survey activities and/or research activities, so the Mixes Narcosis level are limited to 30mt/100ft max.

Gases identification in water is strictly by MOD, however Background of MOD can also add the color codes, notice that monitoring PO2 thru digital gauges in RB is required during training and IDREO projects.
15 pages

One of the keypoints in making a succesful and flexible Decompression strategy is to repeat use between a few gases, as in Standard Mixes for standard applications such as Bottom Mixes and Deco Mixes.

The Standard Mixes should respect parameters reflecting the risk the diver and team agree to cope with, specially in O2 parameters and Narcosis. However is no secret nowdays that "Deep Air " risk is not only Nitrogen Narcosis the "real danger" of breathing Air at depth below 30-40 mts is Oxygen Toxicity the real enemy, which opposed to Narcosis will make diver convulse and loose conciousness. The Oxygen limits applied by IDREO are min .40 PO2 in any RB operation, perferably below .7 and Max 1.0 PO2 at any bottom mix portion of planned dive, 1.2 PO2 on below 90mt deco or short deep exposures, PO2 1.4 on "Deep Deco" or brief NDL dives, 1.6 in 21-6mt deco stops and PO2 2ata inside habitats.

The Explorer don't have necesity or willingness to high level of Narcosis while driving DPV's,  monitoring Rebreather's breathing mixes & gases, navigating thru overhead tunnels, survey activities and/or research activities, so the Mixes Narcosis level are limited to 30mt/100ft max.

Gases identification in water is strictly by MOD, however Background of MOD can also add the color codes, notice that monitoring PO2 thru digital gauges in RB is required during training and IDREO projects.

Quick Video showing properly MOD bottles for the Full range of Deco Gases.

The IDREO Decompression strategy are based in the easiest procedures to have flexible rules to be able to explore the unknown, as in exploration teams are expecting depths changes and extended bottom times, but you just never know in real exploration what is going to happen and from what profile you are going to need to decompress from.

The flexibility apply in exploration Deco Strategy is also desirable and useful for every day diving, we apply it at all levels:




The IDREO Deco Strategy and Deco rules are not magic and need to be understand fully in order to apply them correctly.

IDREO recommended procedures to adjust Decompression in the case of Deco Gas Lost. The reality we face with bottle failures could en up in missing a gas to complete the planned deco, having at hand other breathable gases will allow us to resume the Decompression obligations by Adjustment of the planned stop times.

Understanding how to take advantage of a deco time + deco gas(es) combination thru Decompression Curve Management increases the quality of the time spend at decompression.

Oxygen Window concept focus on highest PO2 exchange possible between tissues and a given period of time. The techniques used as to increase the pressure differential is uderwater Gas Mix switches, to Oxygen Rich Mixes, that can enhance and even accelerated inert gas desaturation from Diver tissues.

Decompression Curve Management is paramount on Diving Decompression Theory.

2 pages

 Many gasses follow the ideal gas law very closely at low pressures. As gas pressures increase blending calculations using the ideal gas law begin to loose a little accuracy. This is because no gas is truly ideal. In most cases the difference in blending plans created using ideal gas verses real gas calculations fall within an acceptable margin of error. iMixer provides both sets of calculations.

The Ideal Gas Law describes the relationships among the four variables temperature (T), pressure (P), volume (V), and moles of gas (n):

p V = n R T

p = absolute pressure (not gauge pressure)

V = volume

n = amount of gas (moles)

R = ideal gas constant

T = absolute temperature (Kelvin)

Real gas laws try to predict the true behavior of a gas by putting in terms to describe attractions and repulsions between molecules. One real gas law is the van der Waals equation:

[P + (n2a/V2)](V - nb) = nRT

P - pressure

V - volume

n - number of moles

T – temperature (Kelvin)

R - ideal gas constant

The first parameter, a, is approximates the attractive forces between molecules while the second parameter, b, is approximates the repulsive forces. Tables for a and b values for a specific gas can be found in many Chemical Engineering textbooks.

If the units of P, V, n and T are atm, L, mol and K, respectively, the metric value of R is 0.0821 while the imperial value is 10.73159. The constants a and b for N2 is 1.408 and 0.03913. For O2 the a and b constants are 1.378 and 0.03183. For He they are 0.03457 and 0.0237.

To calculate the volume of a real gas, V in term n2a/V2 can be approximated as: nR/T (from the ideal gas calculation). Volume and pressure can be calculated with these formulas:

V = nR3T3/(PR2T2+aP2) + nb

P = nRT/(V - nb) - n2a/V2

Calculations using the ideal gas law can be performed in units of pressure (PSI, BAR) or volume (FT3, L3). Computations are simple and easy to validate. Calculations using the van der Walls equation are performed using quantity of gas (mols).

Due to the correction factors a and b approximating the attraction and repulsion of molecules the process of producing a blending plan is a little more complex. We start by figuring out the quantity of the O2, N2, and He components of the starting gas. We then calculate the quantity of gas (in mols) to be added at each step in the process using either O2, He, bank gas, or top off gas. After adding gas at each step we recalculate the pressure and continue adding gas until we reach our target.

A good source for information on real and ideal gasses can be found at SoftChemistry online (

iMixer  can generate blending plans using both ideal and real gas calculations.


Gas Analysis is to verify the gases content within a Mix.
When Air have been enrich with Oxygen to create Nitrox mixes you must verify the Oxygen content by analyzing the bottle.

Is very simple to perform Gas Analysis of a mix content by using a digital gauge + gas sensor unit, it does read the Fraction of the gas usually FO2 but also can be done in Helium.

Oxygen analyzers are most common, Helium analyzers are availble to and t expect to find O2 and Helium analyzers combined in one. Lately CO analyzers are becoming available and a great way to control unreliable gas filling situations or the gas use in those extreme dives.

Gas Analyisis is done to proof Mix against bottle MOD

Rigging a set of two tanks for techincal or cave diving is usually refer to Doubles as they provide redundancy more than just twice as much gas as when diving on traditional single tank set up.

How to Assemble a set of Double Tanks is the starting point to understand where and why the hoses and equipment is placed, the configuration has gone thru continuos evolution since the 1960's matching the equipment development, but also adapting to the new technology such as DPV and Rebreathers.
Nonetheless Open Circuit Doubles is consider by most reliable diving equipment.

The Doubles configuration as core uses a wing and a backplate which are then wingnut bolt to a set of manifold double tanks, each bottle has a first stage and second stage each, one of them is fit with a long hose to facilitate sharing gas in single file thru restrictions or make an ascent separated to avoid buoyancy issues.

Light for comunication and Primary Light source in overhead enviroments is consider part of the Doubles system.
3 pages
All training in IDREO is based on the Accident Analysis in 2011 the main reasin of most fatalities involved switching to the wrong bottle, which means innapropiate Gas Switching Procedures or aids.
 IDREO recomends MOD in all breathing bottles and analyzing before dive any gas used.
As well as a detail list of standard Gases by bottle.
 In this article is discuss many of the important and valuable points to consider when switching bottles adn it's containing breathing gases while underwater either while on Open or Closed circuit.
 Don't forget to look at the videos below in how to perform basic deco bottle and advanced Gas Switching Procedures.

The Basic Deco Bottle Switch Procedure is identify bottle and counter check MOD with the actual depth on depth gauge, make sure your dive partner is supervising your switch and if he or she is distracted just wait. Once you switch wait and supervise your partner gas switch unless you agree for your buddy to do it first, but in any case it should be done one at the time this is the most dangerous part of the dive and team should be fully focus on performing the switch in the safest and more efficient way possible.

In this realistic video a Basic Deco Bottle Switch demo is done as well as a Single Gas Deco bottle switch variation and to be considered as the minimum acceptable need to apply for an IDREO technical diving class.

Most important issue is to verify the gas MOD, buoyancy control second and trim last.

After stage or deco bottle use you may need to perform a Switch to Back Gas, so again make sure you are letting people know in the team as chances are they also may need to do it, however is unlikely if emphasis in proper Dive Planning has been done, however it will be pretty standard with a stage/deco bottle failure.

In this realistic video a Switch to Back Gas demo is done and performace to be considered as the minimum acceptable need to apply for an IDREO technical diving class.


Multiple Gas Switches are required in multiple gas decompression dives or extended penetrations.

In this video are shown in detail the basic steps for bottles rotation, when wearing more than two stages or deco botttles, this skill is to be practice until sequence is memorized and the muscle memory response has been achieved.

The bottle rotation is a skill to be performed when planning to do Multiple Gas Switches.

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Section 5: Rebreather Diving Knowledge
23 pages

Rebreather Explorer Workbook to print and use as part of IDREO Deep Explorer classes.

This Rebreather Explorer Workbook is design to match the information need during participation of a IDREO Rebreather Explorer Class, we have several languages and strive to list the most updated version.
Rebreathers where used in diving before SCUBA diving was availble,
however the complexity of operation and mantenaince some how put them in second place for massive use.

All rebreather follow the same simple features,
nonetheless with some particular choices in injection methods and flow direction.

General information on Rebreather Features is feature in this lecture video.
Rebreather CO2 Scrubbers
3 pages
22 pages

Rebreather Types is about efficiency, NOT injection methods even one type of unit may have several ways of injecting gases to it whic adds to the confusion. Traditionally divers need to catalog units in order to asses risk and therefore injection may play a big role, but a Rebreather Type is directly proportional to it's gas efficiency.


O2 Drop is the IDREO concept related to O2 comsumption while using Rebreather Technology.

The calculation of the O2 Drop strive to monitor and understand the result of Diver metabolism vs  injection of the Oxygen contain within the rebreathing gas inside a given unit. How much Oxygen is consumed and how much is replenished.

There is a few test to perform in order to not only understand the O2 Drop concept but personalize the results,
this test are included in all IDREO Rebreather training and review in the following lectures.

The risk for not knowing your O2 Drop are Hypoxia and DCS.

14 pages

Constant PO2 is a reminiscense of the efforts of early RB technology to proof advantageous to OC diving, however at the technical level is contraproductive and dangerous.

Traditional theory mixes between two gases with a possible big gap between them, usually one of the is pure O2 100%% which beyond traditional recreational limits is potentially a fatality situation.

On the contrary the gases been mixed should have less %% differences to avoid hipoxia and hiperoxia, and should be exchangable by diver during the dive as need. Adding Helium to reduce density and increased narcotic effects.

CCR technology independently of injection method can or cannot be dive using Constant PO2, but what are the advantages and disadvantages ?

1 page

IDREO RB CHECKLIST is the recommended sequence prior to Rebreather Diving

The IDREO RB Efficient test is a very valuable tool in order to monitor the level a Rebreather diver stands.

An accurate and current IDREO RB Efficiency test is paramount in Bailout planning.

This lectures guides you to understanding how to perform an IDREO RB Efficiency test and how to apply it in dive planning and bailout considerations

The IDREO Oxygen Consumtion Rate / Volume Drop Test allows the rebreather diver to identify the partial reduction of rebreather gas volume due to diver metabolism, in fact the inner gas volume in rebreather can be completely depleated as in not possible to creata gas flow and countelrung movement.

The time for the Voume Drop to happen is proportional to the Counterlung size, Diver metabolism and Dive activity intensity following a complete gas injection stoppage inside the unit. Such as running out of gas.

The Volume Drop test bring two keypoints to consideration:

  • One is that in any case the gas inside unit must be of adequate levels when completely depleating the Volume, so we will obtain valuable information to e able to know the Minimum Operating Depths to be using each mix as applied to a particular type of Rebreather unit. In any case avoiding Hipoxia .
  • Exact time of reaction upon a gas supply failure or switch.

Because performing a Volume Drop Test with low O2 content Mixes can lead to Hipoxia, this test should be perform in shallow water with O2, which when quantify for also allows to understand Oxygen Consumption Rate, as diver consumes al O2 thru metabolization, reducing the Volume in a period of time and therefore allowing a quite accurate stimtion of diver O2 Consumtion Rate for giving conditions, rest, swimming or working.


The Partial Pressure of O2 Consumption Rate test, PO2CR test, equipes the Rebreather Diver with the information need to complement minimum operating depth as well as performing the IDREO Gas Cycles.

IDREO CCR Gas Cycles is the amount of time mixes are usable without assistance of O2 rich mixes injection to control PO2 levels, this will be applied everytime an O2 rich injection gas in CCR rebreather fails and/or PO2 levels are intentionally kept low to avoid CNS% count.

To notice that single Gas Operated Rebreathers perform Gas supply switches to stay in the breathable ranges between the MINIMUM & MAXIMUM Operating Depths, ideally to allow safe Gas Cycles even after complete Volume Drop. To notice that OC do just that however there is total Volume Drop and total injection every breath.

A HUD stands for Heads up Display, and what this mean is that traditional rebreather electronics handsets were to bulky to carry at hand or while performing diving activities, so the solution was to allow Rebreather Diver to monitor O2 gas content tru a LED PO2 gauge, in a samll tube attach near the Mask of the Diver.

 The LED Blinking light sequence is one blink per point change in PO2,
and HUD tube can hold up to 3 LED's, one for each sensor.

The HUD leds feature usually three colors as Follows :




The blinking mimics the reaction response need by the diver,
slow motions when all readings are close to normal and
repeatedly continuos blinking and even vibrations follow of a brief pause,
when immediate reaction is need to adjust breathing Mix.

PO2 of 0.9 will be then a single RED blink,
while PO2 0.6 will be 4 continuos blinks follow of a pause,
PO2 0.2 will be 8 continuos blinks follow of a pause

PO2 1.2 will be two blinks on GREEN color,
 while PO2 1.8 will be 8 blinks follow of a pause

The MAV Manual Adition Valve injects gas in a RB unit by diver action of pressing a button, MAV are usually use to aid PO2 Drop and connected to O2 Rich Gas.

The injection must be before the analysis of the MIX, in order to have proper readings, is extremely dangerous to inject gases after the analysis.

If MAV is not working, perform a Flow Check from bottle to QC6 or viceversa, but in one direction verifying QC6 is connected and bottle is open.


While RB Flooding is a possibility when Rebreather Diving, partial operation maybe possible but discourage as is the main reason why Divers and Explorers carry Bailout gas.

Responsible manufacturers will perform complete flooding test before releasing any product in order to identify the best way to clear units from water intrusion as well as buoyancy characteristics.

Using water weight and fluidity combined with gravity you can efficiently clear partial flooding of breathing hoses into CL, furthermore units with canister OPV can be completely cleared even after a complete flooding.


IDREO REBREATHER CONFIGURATION philosohpy is build upon simplicity & consistency among all platforms, the goal is to dive all units with the exact same way of operation, independently of RB Types and/or mounting capabilities, while reducing diver task loading.

The obvious advantages are compatibility among divers and equipment, but extend to gas standardization and decompression mangement.

When Divers and Explorer decide to apply a rebreather unit to the dive mission there are choices of mounting however the most standard way is to wear it on divers back, so call Back Mounted.

Backmounted Rebreather contains the whole Rebreather unit and even considerable size Bailout in one package which has the advantage of moving as a whole unit at the expense of Higher weight. Notice that double Rebreather Back Mount is also possible but quite limited to Cave Exploration without lenghty dry portion excursions between Sumps.

Sidemount Configuration is been available since the 1960's bu mostly taken advantage by eager Cave Divers, lately has become aparent to most recreational Divers and its great. Here are some simple configuration guidance as is not really that hard to figure out, however the planning in order to acomplish other than recreational open water needs to be taken seriously to avoid confusing redundancy needs resulting in extremely complicating a other way simple system.

Side Mount Rebreather Diving is about making diver "Thinner" but simultaneously making it "Widder" is suitable for bedding planes but also maybe more convenient in some diving activities as far to reach dive sites such as sumps.

In fact its convenience and valve monitoring have make it a popular OC activity, however taking it to RB Technology is even lighter !

Side Mount Rebreather Diving is also a great way to increase redundancy in challenging Dives.


An efficient and Safe RB Gas Bottle Switch differs from a Basic Bottle Gas switch as the diver will be doing multiple switches upon descent, bottom and during deco as opposed to a single switch to perform a brief deco stop with a single bottle and therefore less chances of amking the wrong bottle switch.

Furthermore RB Gas Bottle Switch may include doing so while operating Rebreathers and while handelling several different bottles with different Gases, Rebreather and DPV.

As in all Gas Bottle Switches the keypoints are stop all activity and counter check Bottle MOD with Depth gauge and Dive Partner. In this video an RB Gas Bottle Switch is performed by an Explorer at 200ft/60mt before switching to a 120mt/400ft and show the ideal skill need to assure safe and efficient gas switch.

6 questions

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Section 6: Cave and Overhead Diving Knowledge
20 pages

Cave Explorer Workbook to print and use as part of IDREO Cave Explorer classes.

This Cave Explorer Workbook is design to match the information need during participation of a IDREO Cave Explorer Class, we have several languages and strive to list the most updated version.

3 pages

Cave conservation is the protection and restoration of caves to prevent or minimise the effects of human activity.

Some caves have delicate features that can be disturbed by changes in light levels, humidity, temperature or air flow. Caves that have lighting that remains on are prone to having algae grow within the cave changing the appearance and ecology. Speleothems grow as a result of water both on cave surfaces and the humidity of the cave air. Changes to these because of a high number of visitors, changes to the cave air flow and changes to the hydrology will alter speleothem development.

Speleothems can have a slow growth rate and therefore removing them as souvenirs or breakage due to movement within the cave will be visible for a long time, often throughout several generations of human interaction.


The Cave Enviroment is unique and vast of features. The better informed divers are, the most likely divers are to enjoy visiting the Cave diving realm.

Cave Diving features are a result of Cave Formation understanding its basic processes will assist in proper techniques adapt to face it, but as well as building up to the strategy applied for exploring them.

This lectures covers main features of the Cave Diving Enviroment as well as the Cave Formation, diver nomenclature and related topics.

11 pages

Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice, and/or by the force of gravity acting on the particle itself.

Sediments are most often transported by water (fluvial processes), wind (aeolian processes) and glaciers. Beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment also often settles out of slow-moving or standing water in lakes and ocean dunes and loess are examples of aeolian transport and deposition. Glacial moraine deposits and till are ice-transported sediments.

6 pages

The Cave Diving Enviroment Water Quality is awesome and very changeable, caves have different WATER TYPES from fresh to salt and various densities, colors, odors and directly affect diving visibility.


In oceanography, a halocline is a subtype of chemocline caused by a strong, vertical salinity gradient within a body of water. Because salinity (in concert with temperature) affects the density of seawater, it can play a role in its vertical stratification. Increasing salinity by one kg/m3 results in an increase of seawater density of around 0.7 kg/m3.

In the midlatitudes, an excess of evaporation over precipitation leads to surface waters being saltier than deep waters. In such regions, the vertical stratification is due to surface waters being warmer than deep waters and the halocline is destabilizing. Such regions may be prone to salt fingering, a process which results in the preferential mixing of salinity.

In certain high latitude regions (such as the Arctic Ocean, Bering Sea, and the Southern Ocean) the surface waters are actually colder than the deep waters and the halocline is responsible for maintaining water column stability- isolating the surface waters from the deep waters. In these regions, the halocline is important in allowing for the formation of sea ice, and limiting the escape of carbon dioxide to the atmosphere. Haloclines are also found in fjords, and poorly mixed estuaries where fresh water is deposited at the ocean surface.


A Cave Flood is the term use by cave Divers when the water flow of a cave system has gone beyond diveable conditions, current will be to difficult to go against and visibility could been reduced due to sediments stir up.

Flooding are a response of heavy rain and/or periodically snow melts. Caution must be applied when planning dives around adverse enviromental conditions.

16 pages

The Cave Biology inside flooded caves isolate evolution of particular species, we are most likely to interact with Arthropods, Crustaceans, Worms and Sponges. Also in the entrance of the cavern zone, sealife, river life, lake life can be present too.

We have several Guidelines available for our cave diving activities.

There are permanent Guidelines which are always in place and permanently fixed to cave floor and temporary Guidelines which are temporarily place by Divers while diving, this temporary Guidelines are usually removed by the Diver upon exit.

The main Guidelines are :

  • Primary Line
  • Safety Line
  • Jump Lines

Guidelines are usually carried in Reels and Spools by diver, while securely and safely transport in diver suit pockets.
35 pages

Guideline Markers are used in Cave Diving to navigate the permanent lines as well as the temporary guidelines install inside the Cave Main tunnels and side pasages. We have two types of Guideline Markers Directional and NON Directional. Is critical Cave Divers undestand their proper use and applications as will be needed when performing COMPLEX NAVIGATION dives.


Non Directional Markers does not "point" to exit, but rather are left behind as bread crumbs such as "Hansel & Grettel" fairy tale. Non Directional markers can be :





Basics of Team Travel Formation when navigating tunnels and passges with a permanent line.

The lead diver must be the furthest away of the line as it has undisturbed field of vision, the last diver in the team going in is the closest one to the line. The order is maintained but reverse when exiting and therefore also line aproximation.

The first man in runs the line and the last man out remove the teamporary Primary line.


A Simple Navigation is an overhead pentration that requires dive team travel exactly the same path going in than going out, therefore entrance and exit is in a linear form, however the "penetration line" may include a single "T" or "Jump".

Linear Penetration is the most basic form of pentration with Guidelines.

A Primary Guideline is the first temporary line a Dive Team places before entering in the overhead enviroment,
the idea is to connect the permanent main line with a direct contact to surface, so the start tie off, so called Primary Tie off, which is desire to be placed directly under direct ascent to surface; so in Open Water and preferably at 3mt / 10 ft Depth.

From there a second tie off is place directly under the overhead enviroment and preferable Depth is 6 mt / 20 ft. Primary Guideline will eventually be connected with the cave permanent Main Guideline.

Standard procedures to run a Primary Guideline tie offs, visual tips for retrieving it and Primary Reel manipulation is the first Basic Guidelines Skill a Cave Diver should master.

Have a look how divers learn the Basics of line laying, trim buoyancy, comunication are as important as handeling the reel !

You must be capable of running a Primary line if thinkng in diving in the overhead enviroment.

Main line navigation inside the main tunnelo of a cave system can sometime split two ways creating a T, what this mean is that you have to choose direction of travel, when coming back out of the cave obviously is of most importance to go to the exit side !

So leaving a non directional marker will allow you to reinforce the referencing done when deciding to go thru a T junction in the permanent cave guidelines, the marker is placed arm reach from the T and on the direction Diver and Team most travel to go OUT. Minding other teams and guidelines/tieoff wear only one marker per team is enough and in uncommon case of team separation a personal marker can be placed upon travelling back thru the T to let team know you have gone past it to the exit !

To notice that a team performing a jump can create temporary T's in the main guideline or even side passages !

Blind T's are bad placed T junction that maybe miss by Divers and therefore must diving sites involve jumps rather tham T's

Cave Divers can greatly reduce the risk of cave diving by simply maintaining a continuos guideline all the way to the surface, which is the main direct cause of cave diving fatalities.

Permanent lines inside the cave passages are called secondary lines, the main tunnel line is called Main Permament Line, when this lines are connected temporarily we use "JUMPS or GAPS" , as well in a few cases they could be permanently attached forming what is called a "T".


This lecture provide insight in how to run a jump spool.

Jump spool temporarily connect permanent lines to provide a continuos guideline to the surface, when venturing off the main tunnel into side passages, as well as could be employed when attempting to complete a circuit.


A Cave Dive involving Complex Navigation requires continuos decisions regarding guideline navigation, it usually involves several T's and/or jumps, depending of the complexity of the navigation may require several dives to acomplish it.

There are four basic steps to follow :




-Clean up

8 pages

A Restriction is a term use by cave divers to identify reduction in size of a given passage. A restriction can be a a single point or a complete tunnel.

Backmount is ideal for fracture and vertical restrictions, however sidemount configuration is best for bedding planes and horizontal restrictions.

Restricted passages require team formation to be modify, there are two types of restrictions Minor and Major.

Minor restriction forces the team in single file and Major restriction require equipment removal, so call NO MOUNT.

These are the procedures to safely and efficiently perform restrictions during a given dive.


IDREO Open Circuit Cave Sidemount Configuration is aim to divers that do logistics, cave environment shape, prefer not to dive Back mounted rigs.

The IDREO Open Circuit Cave Sidemount Configuration is bit different from the RB Sidemount Configuration, as the bottles are moved from only left to a bottle on the right side.

In this lecture a full land drill presentation on the equipment need, preparation, set up and donning of the IDREO Open Circuit Cave Sidemount Configuration

4 pages

When the cave enviroment features an extensive restricted tunnel passage in horizontal shape such as a tight bedding plane the ideal configuration will be sidemount, however the Gas Management Rules are slightly different than traditional open cave. Due to the inherent possibility of visibility reduction the travel time for the exit portion of the cave on zero visibility following the line touch contact may require substantially longer time than clear water travelling and therefore the most agressive rule to be followed is reserving at least 3/4 of gas supply for the travel out, which is alimit of 1/4 for penetration.

Depending in the amount of gas require and the amount of bottles to carry it the gas management reflects redundancy and possibility of reducing diver size for an emergency exit abandoning fail and empty bottles along the way.

New school of sidemount rebreathers increase dramatically the gas available in smaller configurations increasing the safety in such exposures.


An efficient and Safe Stage Bottle Switch differs from a Deco Bottle Gas switch as the diver will be doing multiple switches upon descent, bottom and during deco as opposed to a single switch to perform a brief deco stop with a single bottle and therefore less chances of amking the wrong bottle switch.

Furthermore Stage Gas Bottle Switch may include doing so while operating Rebreathers and while handelling several different bottles with different Gases, Rebreather and DPV.

As in all Gas Bottle Switches the keypoints are stop all activity and counter check Bottle MOD with Depth gauge and Dive Partner. In this video an Stages Bottle Switch is performed by an Explorer and show the ideal skill level need to assure safe and efficient gas switch.


A Stage Bottle is used during certain stage of a dive, not to be confused with a Deco Bottle. Stage Bottles are only 80ft3/11lt aluminum single tanks and Deco Bottles can be of different sizes with al40/5.5lt aluminum the most common. The Stage Bottles are breath in sequence and to reduce drag are "drop" in the line thru the penetration, in this video we show an ideal stage drop sequence for Stage Bottle Cave Diving.


Awesome Video by White Arrow


Deep Cave Dive Exploration video

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Section 7: Dive Propultion Vehicles
DPV Explorer Workbook
6 pages

Complete DPV Set up allow DPV divers to enjoy efficient DPV diving but also promote safe long term DPV operation.

Battery monitoring, maintenance and burn time prediction is paramount in safe DPV Set up.

Proper Tow leash attachments, buoyancy and trim are the basics in safe and efficient DPV set up.

In order to Build up and expand your DPV activities and planning, we need to establish the DPV Diving Basics.

All you need to know about DPV Diving Basics in a nutshell.

  • How DPV work
  • Basic Battery Burntime Management
  • Electrical Diagram
  • Mechanical Diagram

DPV's have traditional being interested tool for military applications, however researcher and specifically Cave Divers where the ones to quickly visualize a benefit and explore the possibilities of applying this tool to the diving missions.

Cave Diving participation on the development been key in the DPV History design, type , burn time need, which eventually develop in a mangeable more technically advanced unit able to be use by just about any diver.

In this lecture you will get a clear progression of Diver Propultion Vehicles development, including diferent types and applications, which is quite interested education need when deciding to acquire your first DPV or if thinking in upgrading your DPV fleet.

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Instructor Biography

Instructor Biography

IDREO Asia Jason Lim, IDREO Asia Region

IDREO Asia Regional Office for IDREO Exploration Dive Team in Asia. Create the safe and efficient explorer by seminar and training. Support AAP Accident Analysis Project by IDREO .

Instructor Trainer for IDREO in Asia Region . Responsibility for the training standard for future IDREO Instructor in Asia Region. Support the Team growing in every region.

Instructor Biography

Instructor Biography

Instructor Biography

Instructor Biography

Instructor Biography

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