Home › Underwater Speleology › UWS Volume 37 Number 1, January/February/March 2010

In The Loop

Fri, 04/02/2010 - 23:44 — Editor

Text and Photo © Jill Heinerth

When CCR cave divers and open circuit (OC) cave divers dive together, they are referred to as a Mixed Team. OC divers are often reticent about asking a CCR diver about how dive procedures may differ. It is incumbent on the CCR cave diver to ensure that gas management and emergency procedures are clear prior to entering the water.

1. Orientation

  • Show how the rebreather is clipped on and how it can be removed.
  • Demonstrate how the wing is inflated and, if it is attached to an onboard cylinder, discuss how this limited supply could be easily exhausted during a rescue. Determine whether oral inflation of the wing by the buddy is possible.
  • Discuss how developing problems can be recognized.
  • Demonstrate various warning lights, especially those that indicate life-threatening oxygen levels.
  • Describe the significance of a vibrating mouthpiece, if applicable.
  • Describe how and when it might be necessary to close the loop and why preventing a loop flood is critical for buoyancy.
  • Practice sharing gas supplies. Determine whether sharing a long hose or passing off a stage bottle will be a better decision.

 

2. Gas Planning

  • Inquire about the RMV of the OC diver and plan appropriate gas volumes to ensure their safe exit using your open circuit bailout gas.
  • Select bailout gas that is compatible with the OC diver's decompression plans.
  • Plan decompression gases to accommodate all emergency scenarios.
  • Discuss whether the team stays together when they reach decompression stops. The CCR cave diver will likely complete deco much earlier than the OC cave diver.  Will a diver be left alone to complete deco?  If a CCR cave diver leaves early, will they be leaving any of their gas supply behind for the OC cave diver?

3. Complete a Modified S-Drill

  • Describe what to look for during the bubble check. Then rehearse gas-sharing scenarios prior to entering the cave.

Conclusions

If CCR cave divers strive to maintain a high level of conservatism and independence with their bailout gas, the benefits are safety and flexibility. Self-rescue is assured and buddy rescue of a CCR or OC diver is also probable. The goal of the orientation is not to teach the OC diver how to run a rebreather, only how to share gas and handle emergencies that may occur.