TDI Hollis Explorer Rebreather Class 

The Explorer is neither a fully closed circuit Rebreather nor a pure semi-closed system, but an intelligent hybrid that utilizes the best of both worlds. Its compact, lightweight and extremely easy to use.

The Explorer's patent pending design is unique in using a single gas; Nitrox, and is electronically controlled to achieve an optimal balance of PPO2 and dive time. Refillable absorbent cartridges, easy guided setup with go or no go, optional CO2 tracking, and 2 hour duration make this a dream for any recreational diver.

This is the entry-level certification course for recreational divers wishing to utilize a TDI approved semi-closed circuit rebreather (SCR). The objective of this course is to train sport divers in the benefits, hazards and proper procedures for using the Hollis Explorer Sport Rebreather. This course is for Nitrox divers who are interested in using semi-closed circuit rebreathers to extend their bottom time.

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.

Course prerequisites:

  • Minimum age 18, 15 with parental consent
  • Minimum certification of TDI Nitrox Diver or equivalent, may be combined in program at the discretion of the instructor








What you can expect to learn:

The following topics will be covered during this course:

  • History and evolution of rebreathers
  • Comparison of open circuit, closed circuit, and semi-closed circuit rebreathers
  • Practical mechanics of the system
    • Assembly and disassembly of the rebreather
    • Layout and design
    • Scrubber recharge
    • System maintenance
    • Breathing loop decontamination procedures
  • Review of nitrox
    • Dalton’s law (triangle)
    • Optimum nitrox mix
    • Oxygen tracking
    • Gas preparation
    • Dive planning examples
  • Gas physiology
    • Oxygen (O2) toxicity
    • Hyperoxia
    • Hypoxia
    • Asphyxia
    • Hypercapnia
    • Nitrogen absorption
    • Carbon monoxide (CO2) toxicity
    • Gas consumption
  • Formula work and metabolic consumption
    • Oxygen (O2) metabolizing calculations
    • Inspired oxygen (O2) calculations (rebreather equation)
    • Equivalent air depth (EAD)
  • Dive tables
    • Inspired oxygen (O2) table
    • Equivalent air depth
  • Dive computers
    • Mix adjustable
    • Oxygen (O2) integrated
    • PO2 monitoring devices
  • Problem solving
    • Canister flooding
    • Mouthpiece loss
    • Scrubber exhaustion
    • Battery or sensor loss
    • Breathing bag rupture
    • Open circuit bailout system
    • Hyperoxia scenario
    • Hypoxia scenario
    • Hypercapnia scenario
    • Post problem maintenance of equipment
  • Dive and operational planning

Required skill performance and graduation requirements:

The dive depth shall not exceed 1.6 ATM PO2. The following skills must be completed by the student during open water dives:

  • Properly analyze gas mixture
  • Perform all pre dive checks, positive, negative, flow rate, by-pass regulator operation, relief valve pressure, a minimum of 6 times
  • Demonstrate a leak check and repair scenario
  • Demonstration of integrity of exhale counter-lung
  • Properly packing a scrubber canister a minimum of 2 times; if using the ExtendAir cartridge one packing must be with granular material
  • Properly execute set-up and breakdown; a minimum of 6 times for Azimuth or 4 times for Draeger and Submatix ST100 rebreathers
  • Demonstrate adequate pre-dive planning
  • Properly execute the planned dives within all pre-determined limits
  • Properly execute a recovery from a system failure and switch to bail-out stationary a minimum of 2 times
  • Properly execute a recovery from a system failure and switch to bail-out hovering a minimum of 2 times, one of the bail-out scenarios the diver must switch to open circuit and complete dive and safety stop on open circuit; direct ascent must begin when diver switches to open circuit, this scenario should be conducted no deeper than 20 metres/60 feet
  • Properly demonstrate hose clearing technique after each bail-out scenario
  • Perform block switch a minimum of 2 times, Azimuth only
  • Proper PO2 monitoring on all dives, if unit is equipped with PO2 monitoring device
  • Properly execute a mask clearing exercise with emphasis on minimal gas loss
  • Safely and properly execute a buddy out of air scenario, it is preferable the buddy is on a SCR unit also
  • Diver will demonstrate actual safety stops at pre-determined depths
  • Properly execute cleaning and maintenance of the rebreather, including breathing loop decontamination

What’s in it for you?

  • Upon successful completion of this course, graduates may engage in no decompression diving activities utilizing a TDI approved semi-closed circuit rebreather to a maximum depth of 40 metres/130 feet, without decompression; utilizing nitrox mixes not exceeding their level of certification

TDI Hollis Explorer Sport Semi-Closed Circuit Rebreather Diver minimum requirements:

  • Satisfactorily complete the TDI Diving Rebreathers Course written examination with a passing score of 80% followed by 100% remediation by the instructor
  • Complete all open water requirements safely and efficiently
  • Demonstrate mature, sound judgment concerning dive planning and execution

Required Equipment:

The following equipment is required for each student:

  1. Hollis Explorer Sport Rebreather (can be rented for the course)
  2. Personal dive gear to include mask/fin/snorkel
  3. Reel or finger spool.
  4. SMB or lift bag.
  5. Exposure suit adequate for the open water environment.
  6. Access to oxygen analyzer

How Much Does It Cost?

The TDI Hollis Explorer Sport Rebreather Course costs $700 for a group class and private classes 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 Hollis Explorer Sport Rebreather 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 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 Hollis Explorer Sport Rebeather Course you may want to continue your exploration of technical diving by taking the TDI Hollis Prism CCR Class Class.

Maximum depth for the course: 130 feet.