TDI Decompression Procedures

Are you ready to really extend your bottom time? Would you like to safely spend more time looking for meg teeth or exploring the wreck you are on? Then this is the course for you. This is the second foundation course for technical diving and is often taken with the Advanced Nitrox as a joint program.

This course examines the theory, methods and procedures of planned stage decompression diving. This program is designed as a stand-alone course or it may be taught in conjunction with TDI Advanced Nitrox, Advanced Wreck, or Extended Range Course. The objective of this course is to train divers how to plan and conduct a standard staged decompression dive not exceeding a maximum depth 150 feet unless taught in conjunction with the TDI Extended Range Course. The most common equipment requirements, equipment set-up and decompression techniques are presented. Students are permitted to utilize enriched air nitrox (EAN) mixes or oxygen for decompression provided the gas mix is within their current certification level.

Note: Intro To Tech or remedial skills development may be required if the student is unable to demonstrate excellent bouyancy control and other basic skills. This is not the class to try out your new set of doubles for the first time.

Qualifications of Graduates

Upon successful completion of this course, graduates may engage in decompression diving activities without direct supervision provided:

  1. The diving activities approximate those of training
  2. The areas of activities approximate those of training
  3. Environmental conditions approximate those of training

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

  1. TDI Advanced Nitrox.
  2. TDI Extended Range Course
  3. TDI Advanced Wreck Course
  4. TDI Entry Level Trimix Course

Student Prerequisites:

  1. Minimum age 18
  2. Minimum certification of SDI Advanced Diver, Advanced Adventure Diver or equivalent
  3. Provide proof of 75 logged open water dives

Class Duration

The Decompression Procedures Course consists of required pre course homework, a minimum of one evening of classwork, and two full days of diving/training.

Open Water Requirements:

  1. Four dives are required, 2 of those dives must be deeper than 100 feet
  2. If advanced nitrox is taught in conjunction with decompression procedures only a total of 6 dives are required
  3. Only 2 dives from advanced wreck course may be credited towards the total dives required

Academic Subject Areas:

  1. Overview of Decompression Safety Stops Compared to Required Stops
  2. Physics
    1. Pressure review
  3. Physiology
    1. Mechanics of bubble formation
    2. Advantages of hyperoxic mixes for decompression
    3. Nitrogen absorption and elimination
    4. Carbon dioxide toxicity
    5. Ascent / Descent rates
    6. Hyperthermia
    7. Hypothermia
    8. Psychological aspects
      1. Task loading
      2. Stress
      3. Panic
      4. Time management
  4. Equipment
  5. Decompression Options
    1. Air
    2. Nitrox
    3. Oxygen
  6. Equipment Considerations
    1. Twin cylinder or single cylinder option, valve options
    2. Stage cylinder options
    3. Regulator options
    4. Harness / BCD options
    5. Computer, depth gauge, bottom timer options
    6. Ascent and navigation reels
    7. Lift bags/surface marker buoys for drifting or free decompression
    8. Jon-line or Garvin clips
    9. Proper weighting and buoyancy control during dive phase and decompression

  7. Dive Tables vs. Computers
    1. Introduction and review of different models (Buhlmann, DCIEM, US Navy, etc)
    2. Proper use of electronic multi-level dive computers for dive planning and decompression
      1. Mix adjustable
      2. Oxygen (O2 integrated)
  8. Dive Planning
    1. Standard operation
      1. Gas requirements
      2. Oxygen limitations
      3. Nitrogen limitations
  9. Emergency planning
    1. Omitted decompression
    2. Decompression sickness
    3. Equipment failure
  10. Procedures
    1. Primary and decompression gas
      1. Normal operations
      2. Failure, loss or inadequate emergency procedures
      3. Analysis and logging
      4. Safeguards on decompression supply regulators
      5. Rigging and deployment of decompression equipment
    2. Descent
      1. Methods of entry, down lines or free decent
      2. Organization of equipment carried on diver
    3. Ascent
      1. Variable rates
      2. Trim and compensation
    4. Fixed or Drifting Decompression Methods
      1. Up-lines fixed to bottom
      2. Reels and lift bags/surface marker buoys
      3. Free drifting stages or boat supplied
      4. Self-contained versus surface supply / rendezvous gas cylinders
    5. Support
      1. From shore
      2. From descent line or fixed platform
      3. From live-aboard boat

Required Skill Performance and Graduation Requirements:

The following open water skills must be completed by the student during open water dives:

  1. Skills review from previous TDI skills requirements

Land Drills

  1. Selection and preparation of equipment suitable for soft overhead environment
  2. Conduct team oriented drills, buddy checks, for lift bag deployment
  3. Conduct team oriented drills, buddy checks, for gas switching procedures
  4. Gas matching among buddy team
  5. Demonstrate familiarity with basic hand signals
  6. Demonstrate adequate pre-dive planning
  7. Limits based on personal and team gas consumption
  8. Exact dive and decompression profile

Pre-dive Drills

  1. Use START* before every dive
  2. Stress analysis and mitigation

*START is S-drill (OOA drill and Bubble Check), Team (buddy equipment checks), Air (gas matching), Route (entry/exit and planned path underwater), Tables (depth, duration, waypoints and schedule).

In-water Drills

  1. Demonstrate buoyancy control; ability to hover at fixed position in water column without moving hands or feet
  2. Show good awareness of buddy and other team members through communications, proximity and team oriented dive practices
  3. Demonstrate comfort swimming on surface and at depth carrying single decompression stage cylinder
  4. Demonstrate ability to drop and retrieve single decompression cylinder while maintaining position in the water column
  5. Demonstrate ability to deploy a lift bag solo and as member of team
  6. Demonstrate controlled / staged ascent on lift bag / emergency ascent line (lost ascent line)
  7. Remove and replace mask (deploy backup mask)
  8. Demonstrate appropriate reaction to gas hemorrhage from manifold or first stage, SPG and primary regulator
  9. React to BCD inflator malfunction; disconnect LP hose, dump gas and orally inflate BCD/Wing to neutral buoyancy
  10. Demonstrate ability to confirm gas switch(es) at depth with buddy/team members
  11. Buddy breathing decompression gas for at least 1 minute
  12. Switch to back-up mask, remove and replace mask
  13. Demonstrate appropriate reaction to simulated free-flowing decompression regulator
  14. Demonstrate appropriate modifications to deco schedule in decompression emergency (over time, over depth) (to be simulated)
  15. Demonstrate tired diver tow at depth and on surface, 100 feet lateral each
  16. Complete a horizontal breath hold swim at depth for 45 feet
  17. Properly execute the planned dive within all pre-determined limits
    1. Assembly of diver carried equipment
    2. Proper descent / ascent rates
    3. Proper staged stop procedures
    4. Monitoring of decompression status equipment; tables, computers, equipment
  18. Contingency situations and problem solving, as appropriate by instructor
    1. Omitted decompression.
    2. Extended bottom time profiles with increased decompression and recalculated schedules
    3. Failure to deploy lift bag and ree
    4. Missed up-line or missed boat ancho
    5. Loss of decompression gas
  19. A safety stop of at least 3 minutes shall be conducted on all no-decompression dives and proper staged decompression stops whenever and wherever mandated.
  20. Demonstrate (simulated) emergency gas sharing at a stationary depth not to exceed 100 feet
  21. Demonstrate emergency deployment of a backup regulator or bail-out scuba system containing bottom mix at a depth not exceeding 100 feet
  22. Demonstrate the proper deployment, management and use of the bottom mix, decompression mix and travel mix, if used, including but not limited to:
    1. Conservative gas management
    2. Depth control to avoid descending too deep for mix
    3. Show appropriate and timely responses to instruction / signals from the instructor and demonstrate buoyancy control and awareness throughout the dive

In order to complete this course, students must:

  1. Satisfactorily complete the TDI Decompression Procedures Course written examination
  2. Complete all open water requirements safely and efficiently
  3. Demonstrate mature, sound judgment concerning dive planning and execution

Required Equipment

The following equipment is required for each student:

  1. Primary cylinder(s), cylinder volume appropriate for planned dive and student gas consumption
  2. Decompression mix cylinder(s)
    1. Cylinder volume appropriate for the planned dive and student gas consumption with submersible pressure gauge
    2. Labeled in accordance with TDI Standards
  3. Depth gauge and automatic bottom timer and / or dive computer
  4. Regulator(s)
    1. Primary and alternate 2nd stage required on all primary cylinders
    2. Submersible pressure gauges are required on all primary cylinders
  5. Buoyancy compensator device(s) adequate for equipment configuration
  6. Line cutting device
  7. Jon-line and other rigging lines as dictated by site conditions
  8. Ascent reel with lift bag /surface marker buoy
    1. Adequate for maximum planned depth
    2. Minimum of 25 lb lift bag
  9. Oxygen (O2) analyzer; may be supplied by the instructor
  10. Exposure suit adequate for the open water environment
  11. Underwater slate

How Much Does It Cost?

The TDI Decompression Procedures Course costs $375 per student a group class and private courses are available. We schedule students together for group classes whenever possible unless a private class is specifically requested. Military and Public Service discounts are also available.

The course tuition covers your instruction, books, and certification card. Equipment rental (if needed), tank fills, quarry fees, and charter fees are additional.

Note: Participation in the Decompression Procedures Class does not guarantee certification. Each student must complete the required number of dives, all the skills, and demonstrate that they are comfortable with planning and executing safe dives using Nitrox before they receive thier certification. If a student is unable to meet the course requirements additional training may be required.

What's Next?

Once you have completed the TDI Decompression Procedures Course you may want to continue your exploration of technical diving by taking the TDI Trimix Courses.

Maximum depth for the course: 130 feet.