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.
| Category | Backmount | Sidemount DIR | Sidemount Short Hoses |
| Advantages | Simpler 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 |
| Disadvantages | Manifold 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 |
