In the fourth quarter 2008, PADI Undersea Journal, Mark Caney and Karl Shreeves write about the state of recreational diving and the likelihood of rebreathers finding a home in a basic diver’s hands. In this insightful article, the pair outlines their thoughts about what characteristics an “ideal” recreational rebreather would possess. They combed through incident and accident reports and spoke to both manufacturers and instructors to conclude that a recreational rebreather should have the following features, before going mainstream:
- A very simple status indicator in divers’ line of sight, e.g, green – all is well; amber/orange – check something; red – bail out.
- Divers should be able to switch to open circuit bailout without removing their mouthpiece, using a single, one-handed action.
- 3. The unit initiated or warns* the diver if the electronics are not turned on at the beginning of the dive.
- The unit warns divers if they start to use it with the diluent or oxygen supply not properly turned on, or turns on the relevant gas automatically.
- The unit warns the diver is the diluent or oxygen supply becomes too low.
- The unit warns divers if the scrubber approaches exhaustion or gets bypassed (channeled).
- The unit won’t operate or warns divers if the scrubber canister is missing or incorrectly installed.
- The unit uses pre-packed CO2 scrubber cartridges.
- The unit warns divers if the loop floods to dangerous levels.
- The unit warns the diver if the electronics fail. Manual switching to open circuit is possible in such a situation
- The unit maintains a near constant PO2 in normal, level depth use, and adjusts fraction of oxygen.
- The unit warns divers if the PO2 varies too high or too low from set point.
- The unit should either reasonably sustain a diver or make diving impossible if pre dive procedures are not followed correctly.
- The unit functions to a depth of 50 meters/164 feet.
- The unit should be of robust design and engineered so it cannot be assembled incorrectly and still reasonably be thought operable.
*Warnings are defined as distinct alerts that cannot be reasonably be ignored nor overlooked. A vibrating mouthpiece alarm is ideal, coupled with a visual alarm in the diver’s line of sight and/or audio alarm.
After defining their wish list, Caney and Shreeves continue to pay close attention to new units that come to market. Although nothing currently meets their outline, units like the new Poseidon Discovery are getting close. The PADI organization and DSAT (Diving Science and Technology) are not ready to look at developing course curriculum for anything currently on the market, but they will continue to keep their eyes open for future technologies with promise.
Technical divers can use the wish list as food for thought. Does your rebreather fulfill any of their fifteen points? If not, are you able to detect or prevent the situations described? Does your check list and pre-dive procedure prevent the above situations? It is a worthy review that should leave you practicing!
Safe diving!
