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TDI – Entry Level Trimix Diver Course
Introduction
The TDI Entry Level Trimix Course provides the training required to competently and safely utilize breathing gases containing helium for dives that require staged decompression, utilizing Nitrox and / or oxygen mixtures during decompression to a maximum depth of sixty (60) msw / two hundred (200) fsw. The objective of this course is to train divers in the benefits, hazards and proper procedures of utilizing custom oxygen / helium / nitrogen mixtures as breathing gases. Gas mixes are not to have any less than eighteen (18%) percent O2.

Qualifications of Graduates
Upon successful completion of this course, graduates may engage in technical diving activities utilizing custom Trimix mixtures without direct supervision as long as:
1. The diving activities approximate those of training.
2. The areas of activities approximate those of training.
3. Environmental conditions approximate those of training.
4. Oxygen percentages are twenty one (21) percent or higher.

Who May Teach
Who may teach this course:
1. Any active TDI Entry Level Trimix Instructor may teach this course.

Student – Instructor Ratio
Academic:
1. Unlimited, so long as adequate facility, supplies and time are provided to insure comprehensive and complete training.
Confined Water (Swimming pool-like conditions):
1. N/A.
Open Water (Ocean, lake, quarry, spring, river or estuary):
1. A maximum of four (4) students per Instructor. However, it is the instructor’s discretion to reduce this number as conditions dictate.

Student Pre-Requisites
The student must:
1. Be a minimum age of eighteen (18).
2. Have a minimum certification as a TDI Advanced Nitrox Diver and Decompression Procedures Diver (or equivalent).
3. Show proof of a minimum of one hundred (100) logged dives.

Course Structure and Duration
Open Water Execution:
1. Four (4) decompression dives is required with a minimum accumulated bottom time of one hundred (100) minutes.
2. Two (2) of the dives should be deeper than forty (40) msw / one hundred thirty (130) fsw.
3. Two (2) dives may be credited from the TDI Extended Range course (or equivalent) at the discretion of the Instructor.
4. Only two (2) dives from Advanced Wreck course may be credited towards the total dives required.
Course Structure:
1. TDI allows instructors to structure courses according to the number of students participating and their skill level.
Duration:
1. The minimum number of classroom and briefing hours is eight (8).

Administrative Requirements
The following is the administrative tasks:
1. Collect the course fees from all the students.
2. Ensure that the students have the required equipment.
3. Communicate the training schedule to the students.
4. Have the students complete the Liability Release and Medical history forms.
5. The Instructor should review the Liability Release and Medical Forms before starting on the course.
Upon successful completion of the course the Instructor must:
1. Complete the Student Registration Form and send the Registration Form to TDI HQ.
2. Award card and certificate.

Required Equipment
The following are required for this course:
1. TDI Trimix Manual.
The following equipment is required for each student:
1. Bottom Mix Cylinder(s)
A. Cylinder volume appropriate to complete all planned decompression on bottom mix.
B. Dual outlet valve, double manifold or independent doubles.
C. Labeled in accordance with TDI Standards.
2. Decompression Mix Cylinder(s)
A. Cylinder volume should contain a minimum of 1.5 times the gas required for the planned decompression.
B. Labeled in accordance with TDI Standards.
3. Suit Inflation Cylinder (required for dry suit divers only).
4. Regulators
A. Primary and primary redundant required on all bottom mix cylinder(s).
B. Submersible pressure gauges are required on all primary / bottom mix cylinders.
C. A contingency use long hose second stage should be designated and appropriately rigged to facilitate air sharing at depth if necessary.
D. It is strongly recommended that three (3) required regulators be all DIN or all yoke.
5. Buoyancy Compensator(s) adequate for equipment configuration.
6. Redundant Depth and Timing Devices.
7. Air decompression computers allowed for use as depth and timing devices.
8. Redundant Light System if required by site.
9. Ascent Reel with Lift Bag/Surface Marker Buoy
A. Adequate for maximum planned depth.
B. Minimum of twenty three (23) kg / fifty (50) lb. lift bag (a dump valve highly recommended).
10. Exposure suit adequate for the open water environment.
11. Line Cutting Device.
12. Underwater Slate (for decompression / contingency tables).

Required Subject Areas
The TDI Trimix Manual is 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 this course:
1. Physics
A. Pressure review.
2. Physiology
A. Hypoxia.
B. Oxygen toxicity.
I. Whole Body (OTU5).
II. Central Nervous System (CNS).
C. Nitrogen Narcosis.
D. Nitrogen and Helium absorption and elimination.
E. Carbon Dioxide Toxicity.
F. Carbon Monoxide Toxicity.
G. Helium
I. HPNS.
II. Effects on respiration
III. Effects as an insulator.
H. Counter Diffusion.
I. Hyperthermia.
J. Hypothermia.
4. Decompression Options
I. Air.
II. Nitrox.
III. Helium.
3. Equipment Considerations
A. Cylinder options.
B. Stage cylinders options.
C. Suit inflation options.
D. Regulator options.
E. Harness / BC options.
F. Computer / depth gauge / bottom timer options.
G. Ascent and navigation reels.
H. Lift bags/surface marker buoys.
I. Lights.
J. Redundant mask and knife.
K. Jon-line.
4. Dive Tables
A. Computer generated tables.
B. DCIEM Heliox Tables and I or other published tables.
5. Dive Planning
A. Operational Planning
I. Support.
II. Teams.
B. Team Planning
I. Gas requirements.
II. Oxygen limitations.
III. Inert gas limitations.
C. Emergency Planning
I. Omitted decompression.
II. Oxygen toxicity.
III. Analysis and logging.
IV. General.
6. Procedures
A. Bottom, Travel and Decompression Gas
I. Normal operations.
II. Failure, loss or inadequate emergency procedures.
III. Analysis and logging.

Required Skill Performance and Graduation Requirements
The following open water skills must be completed by the student during open-water dives. It is recommended that all dives be conducted between thirty (30) msw / one hundred (100) fsw and sixty (60) msw / two hundred (200) fsw. Gas mixes are not to have any less than eighteen (18) percent O2.
1. Properly analyze all gas mixtures to be used.
2. Demonstrate adequate pre-dive planning
A. Limits based on personal and team gas consumption.
B. Limits based on oxygen exposures at planned depths for actual mixes.
C. Limits based on inert gas absorption at planned depths with actual mixes.
3. Properly execute the planned dive within all pre-determined limits.
4. Demonstrate the proper navigational techniques for the specific dive.
5. On two (2) of the dives, demonstrate an ascent with ascent reel and lift bag and perform staged decompression
6. Demonstrate the proper procedures for switching and isolating a malfunctioning primary regulator. (This exercise should not be practiced deeper than forty (40) msw) / one hundred thirty (130) fsw
In order to complete this course, students must:
1. Satisfactorily complete the TDI Trimix Course written examination.
2. Complete all open water requirements safely and efficiently.
3. Demonstrate mature, sound judgment concerning dive planning and execution.
Updated 24 May 2003