Dual rebreathers in practice: example experiences from the Wetmules and COBRA Divers

Area of Science:

• Marine Biology
• Oceanography
• Diving Science

Background:

• Closed-circuit rebreathers (CCRs) are crucial for technical diving.
• Traditional open-circuit bailout is impractical for extreme dives.
• Dual rebreather systems offer a solution for extended range diving bailout.

Purpose of the Study:

• To present operational experiences of dual rebreather configurations.
• To compare contrasting approaches developed by Wetmules and COBRA Divers.
• To identify benefits and challenges of dual rebreather use in technical diving.

Main Methods:

• Independent development of dual rebreather practices by two teams.
• Extensive field testing and evolution of contrasting approaches (partial integration vs. full independence).
• Development of techniques for managing inactive rebreather status (gas content, buoyancy, fault detection).

Main Results:

• Dual rebreathers significantly reduce open-circuit bailout needs, enabling greater depth and penetration.
• Operational insights include managing inactive loop gas, integrity checks, and buoyancy.
• Challenges identified: increased task loading, maintenance, and novel failure modes in inactive units.

Conclusions:

• Dual rebreathers extend operational capabilities but introduce significant complexity.
• While offering benefits like eliminating emergency gas switches, inactive rebreathers pose risks of undetected failures.
• Contrasting integration vs. independence strategies depend on operational priorities, demanding high operator proficiency.