Karl's Rebreather "Surprise" Page
This page is a compendium of, in the main, links to other people's contributions regarding "surprises" in various rebreathers. It is NOT approved or sanctioned by any training agency or builder; indeed, it is specifically here outside of the control of both agencies and manufacturers so that it is available to all, whether you pay someone for "training" or not!
Why put this list up? Because it appears that a material number of rebreather diving accidents can have their root causes traced to one or more "surprises" that the user experienced while the device was underwater.
Defined: A "surprise" is an undocumented and unexpected problem that occurs underwater as a consequence of either the fundamentals of unit design or the specifics of a given implementation. Underwater, surprises are BAD and can KILL.
We can prevent some of these deaths by removing the "surprise" element of these issues. Many if not most of these "surprises" either have engineering or operational fixes which will make them either less likely to occur or, in some cases, not happen at all. In some cases the only real fix may be an engineering change and recall by the manufactrurer; in this case it is my hope that listing these publically manufacturers will be pressured to adopt these changes in their hardware and unit firmware, and when necessary, recall their units in the field to fit these repairs.
There is a page for each unit that has one or more "surprise" listed, as well as several generic surprises listed here on this top level page. To be listed in the unit-specific page a user of the unit must post, in a public place where I can link to it, a description of the "surprise", how to verify it, and the unit make, model and serial number on which it was observed. If it is known when that "surprise" was corrected, that is also helpful but it is not necessary.
I will not take anonymous reports, nor will I be the repository for the report itself - only the link. For obvious reasons (I don't own these units generally-speaking) I also am neither able to verify or refute any claimed "surprise". If the original poster decides to take down his original "surprise" posting because he was in error, and notifies me, I will remove the index entry. If a manufacturer corrects a "surprise" and the original poster or some other party verifies this I will so note it, but the surprise listing will remain unless the manufacturer provides evidence of a recall, at no cost to owners, that has corrected ALL of the exisitng in-use units.
Generic Surprises on nearly all eCCRs
| Entry Date | "Surprise" Description |
Potential Fix(s) |
| 12-28-2006 | On essentially all eCCRs, there is no validation performed of an oxygen sensor's ability to read hyperbaric (> 1.0 PO2) oxygen content prior to use, yet most if not all units will permit setting a PO2 of greater than 1.0. This is a serious problem because oxygen sensors, when they fail, tend to become "current limited" and thus read ok at lower PO2s, but fail to register higher ones. The consequence of this is that one or more sensors may show a perfectly acceptable loop PO2 yet the loop may be dangerously hyperoxic (> 1.6), leading to a CNS oxygen toxicity hit without warning. Calibration at 1 ATA (the surface) cannot detect this fault. | Manufacturers could modify their eCCR firmware to insist that the oxygen sensors in their units prove their ability to read hyperbaric PO2s before allowing setpoint control over 0.9. Specifically, unit firmware could demand that a diver "validate" the high-PO2 response of the sensors at 20' (on 100% O2, for a PO2 of 1.6) on an interval before allowing elevated-PO2 use. |
Unit-Specific "Surprise" lists