IEC 61508 Safety Case: Learning from accident data

Data on rebreather accidents is needed by all involved with rebreathers, for developing safety cases and for business assessment.

The database published here is maintained by Deep Life Group as part of our Group Functional Safety management.  It comprises 4 categories of information:

  1. Comprehensive database of fatal rebreather accidents.
  2. Tools and example data enabling the significance of accidents to be assessed statistically.
  3. Training Material on rebreather accident investigation and associated data.
  4. Summary of incidents and accidents for training purposes.

Please report any new accidents or serious incidents to the Coordinator at Deep Life

Paper revealing the dichotomy within the sports rebreather industry, where limited budgets result in some companies spending on marketing at the cost of engineering, and the actual consequences of those decisions.

Rebreather Fatal Accident Database to 4th April 2024 with analysis (1.8MB))
The public extract of the database of Rebreather Fatal Accidents and analysis, listing 658 of the confirmed rebreather fatal accidents. Manufacturers can use this data to improve designs, instructors can use it to improve training, and divers can learn from it too. This list names the divers where these are in the public domain, to enable the accuracy of the list to be verified more easily by third parties. The main lessons for divers are:

  1. Check your rebreather. Diving non-CE rebreathers means the diver may be diving an entirely untested product regardless of how reputable the brand name is,. Untested rebreathers generally have lethal design faults. Only dive CE rebreathers certified by reputable agencies such as SGS or DEKRA.
  2. Check oxygen cells every 3 months with a cell checker, and look after them.
  3. Change your scrubber within the manufacturer's stated endurance for the dive profile you plan with either a Micropore EAC, Draeger Divesorb or Molecular Products Sofnolime - do not use other scrubber materials, particularly do not use medical absorbant, e.g. Spherasorb.
  4. Always replace your O2 cells after a year of service,or within 18 months after manufacture - whichever comes first.
  5. Always have eCCR electronics serviced annually even though manufacturers generally do not require this. Essential safety corrections are made during annual servicing.
  6. Never go solo rebreather diving: it is not Open Circuit so the diver is unaware of exactly when a rebreather fails.
  1. Do all predive checks, and never dive a rebreather that fails any check or that you have not fully checked or that you know to be faulty in any way.
  2. Key Check: Before every dive unplug the hoses from the scrubber or counterlungs, check each of the two one-way valves work, then plug the hoses back in. If you are not sure how to check the valves in-situ, then do not dive: ask another rebreather diver to demonstrate and then practice doing it until it is second nature.
  3. Key Check: Do both positive and negative pressure tests. They should hold solid.
  4. Pre-breathe for at least 5 minutes to check your PPO2 is under control and CO2 scrubber is working,
WHEN DIVING any rebreather with electronics:
  1. Look at your PPO2 on entry,
  2. Look at your PPO2 at least every minute on initial descent,
  3. Look at your PPO2 at least every 4 minutes on the bottom,
  4. Look at your PPO2 continuously during ascent.
  5. If your ALV (ADV) fires when you are not descending, immediately inject a burst of O2 manually and do then do a flush to check your controller is working and the displayed PPO2 is correct. The ALV may be giving you your only warning that the loop is becoming hypoxic.
  6. !! Never ascend on a rebreather if you cannot see your PPO2. !!
  7. Always use rebreathers as pure oxygen units when near the surface. Do not exceed 8m on pure oxygen (a PPO2 of 1.6 if flushed less than 5 times)
  8. Keep alert for CO2 problems: increasing breathing rate, fear or discomfort. Bail out immediately you suspect there may be any CO2 problem.
  9. !! When a diver aborts a dive, for any reason, the buddy MUST stay with him. It is the time when the diver will likely most need a buddy. Abandoning a diver aborting a dive may be manslaughter!!
  1. Inject Make-up-gas (DIL) manually, then think.
    Hypoxia kills without warning, so flushing should be an automatic reaction drilled into you when a problem occurs. If you suspect hypercapnia (excess CO2) then bail out first, as you will not be able to later.
  2. Do NOT ascend.
  3. Do NOT continue on RB without injecting gas manually.
  4. If in doubt, bail out. If you do not know your PPO2, then you must bail out immediately: your life depends on it.


Risk Analysis Toolkit with Sports Rebreather Database. Updated to 9th May 08
The toolkit enables different types, models and versions of rebreather to be compared for safety based on observed accidents. The spreadsheet also provides tools for the assessment of rebreather accident risk and potential liability. Excel macros must be enabled to use this toolkit. A database for the sports rebreather market is provided as an example, from which is calculated the global sports rebreather market size, revenue, accident risk and liability to net margin. The database is also used to illustrate how safety can be quantified, comparing the risk of using mCCR versus eCCR as one example and the changes to particular rebreather models as another. Changes may including training and use.

Note: Commercial, Military and Professional rebreathers have a much lower risk, and data on these is provided under Non-Disclosure to companies working with Deep Life Ltd.

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Rebreather Accident Analysis: a short tutorial guide (59KB)
A short tutorial guide on the main steps in investigating a rebreather accident, for use as forensic training material.

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How Rebreathers Kill People (68KB)
Incident reports showing some of the critical failures in rebreather design, and the actions that need to be taken to address them.

Effect of water ingress on the breathing resistance of scrubbers using granular CO2 absorber (175KB)
Forensic report on the effect of water ingress on breathing resistance in a typical granular scrubber. Report enables packing to be assessed in rebreathers recovered after an accident where the equipment is flooded.