Gas Sharing Procedures

by | Feb 23, 2025 | Cave Diving

Emergency Gas Sharing Procedures: Backmount vs. Sidemount

1. Gas Sharing in Backmount Configuration

  • Primary Long Hose Donation:
    • Out-of-air diver receives the primary long hose regulator
    • Donor switches to their backup regulator (necklaced secondary)
    • Exit the cave in a controlled, single-file formation
  • Potential Issues:
    • Limited self-sufficiency; requires reliance on team
    • Restricted problem-solving in low-visibility or high-stress situations
    • Manifold failures can lead to cascading gas loss

2. Gas Sharing in DIR Sidemount Configuration

  • Use of Long Hose for Donation:
    • Similar to backmount DIR, out-of-air diver takes the long hose
    • Donor breathes from the short hose attached to the opposite tank
    • Maintains some redundancy but follows backmount-style procedures
  • Potential Issues:
    • Complex switching process may be unnecessary for sidemount divers
    • Restricts the self-sufficiency advantages of independent sidemount tanks

3. Gas Sharing in Two Short-Hose Sidemount Configuration

  • Tank Donation Instead of Hose Donation:
    • Out-of-air diver receives an entire tank, ensuring complete self-sufficiency
    • Allows for unrestricted movement through restrictions
    • Avoids the need for tethering divers together with a long hose
  • Advantages:
    • Maximizes redundancy and self-sufficiency
    • Simplifies gas-sharing procedures in confined environments
    • Reduces the likelihood of entanglement or restricted mobility

4. Why Two Short-Hose Sidemount is Preferred

  • Independent problem-solving: Each diver maintains self-sufficiency without relying on team adjustments.
  • Better mobility: Unlike long-hose methods, divers remain untethered, allowing for more efficient movement in restrictions.
  • Greater safety in gas failure scenarios: Divers don’t risk losing both tanks due to a single failure, ensuring at least one fully operational tank.

In summary, while traditional gas-sharing methods in backmount and DIR sidemount configurations focus on hose donation, the two short-hose sidemount system provides superior self-sufficiency, safety, and ease of movement, making it the preferred choice for many modern cave divers.

CategoryBackmountSidemount DIRSidemount Short Hoses
AdvantagesSimpler gas switching
Commonly used in technical diving
Integrated gas system
Familiar to backmount divers
Long hose allows gas sharing through restrictions
Independent tanks prevent total gas loss
Better self-sufficiency
Easier problem-solving
More efficient in confined spaces
DisadvantagesManifold failure can lead to total gas loss
Difficult gas shutdown drill
Tanks are not visible for self-checks
Still requires hose management
Less efficient in self-sufficiency than short hose sidemount
Requires frequent regulator switching
Gas sharing requires full tank donation instead of a hose
Not as commonly trained in all agencies

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