TDI CCR Helitrox Decompression Procedures

This is the second level certification course for divers wishing to utilize a Closed Circuit Rebreather (CCR) for mixed gas diving using a Helitrox Diluent.
The objective of the course is to train divers in the benefits, hazards and proper procedures for diving a CCR and to develop basic CCR diving skills, to a maximum
of 45 metres/150 feet, using an air/nitrox/helium diluent for formal decompression diving. Students are permitted to utilize a diluent and bailout mix with no greater
than a 20% helium content and no less than a 21% oxygen content, and are permitted to use up to 100% oxygen for decompression.

Who this course is for:

The certified TDI Air Diluent Diver (or equivalent) who is looking to extend their depth limitations, learn CCR decompression procedures, and reduce narcosis
The open circuit TDI Advanced Nitrox and Decompression Procedures or Helitrox Diver looking to utilize CCR technology to extend their depth limits and bottom times

Course prerequisites:

Minimum age 18
Proof of 50 logged dives
Minimum certification level of TDI Advanced Nitrox Diver, Deco Procedures Diver or Helitrox diver or equivalent from agencies recognized by TDI
If the rebreather is a TDI approved sidemount rebreather, the student must hold the TDI Sidemount Diver Certification or equivalent and provide proof of 10 logged sidemount dives

OR
Minimum age 18
TDI Air Diluent CCR Diver certified or equivalent
30 hours on the CCR unit
Six months CCR diving experience

What you can expect to learn:

The TDI Diving Rebreathers Student Manual and the manufacturer’s manual are mandatory for use during this course but instructors may use any additional text or materials that they feel
help present these topics. The following topics must be covered during the course:
History and evolution of rebreathers
Comparison of open circuit, closed circuit and semi closed circuit rebreather systems and the benefits/problems with each
Practical mechanics of the system Assembly and disassembly of the unit
Layout and design of the unit
Absorbent canister design and maintenance
Proper packing of canister, in accordance with manufactures recommendations
Breathing loop de-contamination procedures
Manufacturer supported additional items (automatic diluent valve, etc.)

Gas physiology Oxygen toxicity
Nitrogen absorption
CO2 toxicity
Gas consumption

Electronic and manual systems design and maintenance O2 metabolizing calculations
Fuel cells Maintenance
Replacement
Manufacturing date

System electronics functionality and calibration procedures

Dive tables Constant partial pressure of oxygen (PPO2) theory
Central nervous system (CNS) and awareness of oxygen tracking units (OTU)

Dive computers Mix ajustable
Constant PO2
O2 integrated

Dive planning Operational planning
Gas requirements including bailout scenarios
Oxygen limitations
Nitrogen limitations

Emergency procedures Use of B.A.D.D.A.S.S.
Three H’s problems
Flooded loop
Cell warnings
Battery warnings
Bailout gas requirements

Helium considerations Helium absorption and elimination
Advantages of hyperoxic mixes for decompression
Advantages of helium for bottom gas
Hypoxia
HPNS
Effects on respiration
Effects as an insulator
Helium limitations

Required skill performance and graduation requirements

All standards set by both TDI and the rebreather manufacturer must be met, while maximum limits of neither may be exceeded.

The following open water skills must be completed by the student during open-water dives with the following course limits:
All open water dives must be between 9 metres/30 feet to 45 metres/150 feet
Two dives must be deeper than 20 metres/66 feet and one dive must be deeper than 30 metres/100 feet
PO2 not to exceed manufacturer recommendation or a working limit of 1.3 bar
All dives to be completed within CNS% limits with a recommend maximum of 80% of the total PO2 CNS limit
Safety stops to be conducted with a minimum 3 minutes at 6 metres/20 feet
Where the user opts for an automatic diluent valve (ADV) fitted by the manufacturer additional skills such as regular diluent gauge monitoring and addition control must be emphasized
Calculate all off board gas at 45.3 litres/1.06 cubic feet per minute usage to cover stress situations
All dives to be completed within appropriate constant PO2 decompression tables
Student is only certified for Helitrox decompression diving on the specific CCR unit
Students must do one bailout from depth on o/c to include simulated decompression

Open Water Skills:

Pre dive checks Unit build-up
Scrubber packing
Positive and negative checks

Verify diluent and O2 cylinder contents using O2 analyzer where appropriate
Demonstrate correct pre dive planning procedures including Limits based on system performance
Limits based on oxygen exposures at chosen PPO2 levels
Limits based on nitrogen absorption at planned depth and PO2 set-point
Thermal constraints

Emergency procedures Mouthpiece familiarity drills
Gas shutdowns and loss of gas
Broken hoses
Flooded absorbent canister
CO2 breakthrough
Semi-closed mode
Low oxygen drills
High oxygen drills
Flooding loop
Electronics and battery failure
Properly execute the ascent procedures for an incapacitated CCR diver

Use of BCD/suit and effective management of loop breathing volume for buoyancy control
Stop at 3-6 metres/10 – 20 feet on descent for leak bubble check
Electronics systems monitoring for PO2 levels (SETPOINT) and switching set-points
Manual control of set-point if electronically controlled CCR is not used
Use of lift-bag/delayed surface marker buoy and reel
Proper execution of the dive within all pre-determined dive limits Constant-loop volume management

Post dive clean of unit to avoid contamination and spread of disease

If this is the first CCR course taken the following must be included:

Post dive clean of unit Mouth piece and hoses
Clean and disinfect unit
Inspect components of unit

Dive maintenance of unit Cell remove and replace
Mouth piece strip and rebuild
Replacing batteries

Decompression related in water skills:

Demonstrate comfort swimming on surface and at depth carrying 1 bailout/decompression cylinder
Demonstrate ability to drop and retrieve one bailout/decompression cylinder while maintaining position in the water column
Demonstrate ability to deploy SMB or lift-bag solo and as a member of a team
Demonstrate appropriate reaction to gas hemorrhage from manifold or first stage, SPG and primary regulator
Demonstrate appropriate reaction to simulated free-flowing deco regulator
Buddy breathing deco gas for at least 1 minute
Oxygen rebreather mode at less than 6 metres/20 foot stop
Complete 1 bailout scenario at depth to include decompression obligation on open circuit

What’s in it for you?

Upon successful completion of this course, graduates may engage in decompression diving activities utilizing a CCR without direct supervision provided:
The diving activities approximate those of training
The areas of activities approximate those of training
Environmental conditions approximate those of training

Upon successful completion of this course, graduates are qualified to enroll in:

TDI Mixed Gas CCR unit specific course

TDI Helitrox Diluent CCR Decompression Diver minimum requirements:

Satisfactorily complete the written examination with a pass mark of 80% and 100% remediation
Complete to the instructor’s satisfaction all confined and open water skill development sessions
Demonstrate mature, sound judgment concerning dive planning and execution
Course must be completed within 6 weeks from the starting date
Complete a refresher course following a period of inactivity greater than 6 months following the course