SNSI Semi-Closed Circuit Rebreather Course

This is the entry-level certification course for recreational divers who want to use an SNSI-approved semi-closed circuit (SCR) rebreather. The purpose of this course is to train sport divers in the benefits, dangers, and proper procedures for using an SCR.

Who is this course for:

• Nitrox divers interested in using semi-closed circuit rebreathers to extend their bottom time.

Course prerequisites:

• Minimum age 18, 15 with parental consent
• Minimum SNSI Nitrox Diver certification or equivalent may be combined into the program at the instructor's discretion.

What you can expect to learn:

The SNSI Diving Rebreathers Student Manual and manufacturer's manual are required for use during this course, but instructors may use any additional text or material they feel will help introduce these topics. The following topics should 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
  • purifier recharge
  • system maintenance
  • Breathing circuit decontamination procedures
• nitrox review
  • Dalton's law (triangle)
  • Optimum nitrox mix
  • oxygen tracking
  • gas preparation
  • Examples of dive planning
• gaseous physiology
  • Oxygen toxicity (O2)
  • hyperoxia
  • hypoxia
  • suffocation
  • hypercapnia
  • Nitrogen absorption
  • Carbon monoxide (CO2) toxicity
  • gas consumption
• Formula of work and metabolic consumption
  • Oxygen metabolism calculations (O2)
  • Inspired oxygen (O2) calculations (rebreather equation)
  • Equivalent air depth (EAD)
• diving tables
  • Inspired oxygen table (O2)
  • Equivalent air depth
• dive computers
  • adjustable mix
  • Integrated oxygen (O2)
  • PO2 monitoring devices
• Problems solution
  • canister flooding
  • mouthpiece loss
  • purifier exhaust
  • Battery or sensor loss
  • Respiratory sac rupture
  • Open circuit rescue system
  • Hyperoxia scenario
  • hypoxia scenario
  • hypercapnia scenario
  • Equipment after-problem maintenance
• Diving and operational planning

Necessary skill performance and graduation requirements

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

• Properly analyze the gas mixture
• Perform all predive checks, positive, negative, flow rate, bypass regulator operation, relief valve pressure, a minimum of 6 times
• Demonstrate a leak check and repair scenario
• Demonstration of expired counter-lung integrity
• Properly pack a depuration container at least 2 times; if using ExtendAir cartridge a package should be with granulated material
• Correctly perform assembly and disassembly; a minimum of 6 times for Azimuth or 4 times for Draeger and Submatix ST100 rebreathers
• Demonstrate proper pre-dive planning
• Properly execute planned dives within all predetermined limits
• Correctly perform a crash recovery and switch to stationary bailout a minimum of 2 times
• Correctly perform a system failure recovery and switch to hover rescue a minimum of 2 times, one of the rescue scenarios where the diver must switch to open circuit and complete open circuit dive and safety stop; direct ascent should begin when the diver switches to open circuit, this scenario should not be conducted at a depth no greater than 20 metres/60 feet
• Properly demonstrate hose cleaning technique after each rescue scenario
• Perform block swap minimum 2 times, Azimuth only
• Proper PO2 monitoring on all dives if unit is equipped with PO2 monitoring device
• Correctly perform a mask-clearing exercise with an emphasis on minimal gas loss
• Safely and properly run an off-air buddy scenario, it is preferred that the buddy is on an SCR unit as well
• Diver will demonstrate real safety stops at predetermined depths
• Properly perform rebreather cleaning and maintenance, including breathing circuit 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, no decompression; using nitrox blends that do not exceed their certification level

Minimum SNSI semi-closed circuit rebreather diver requirements:

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