Hi All, I found this recently at (
www.deeplife.co.uk/or_files/RB_Fatal_Accident_Database_100725.xls). Not a rebreather diver myself so merely passing on the info
Date Wed 06 Sep 2017
Location China, Hebei Province, Panjiakou, underwater section of ancient Great Wall
Deceased's Name Chinese Female
Rebreather involved JJ-CCR, JJ-BOV
Electronics fitted to rebreather for PPo2 Monitoring or Control Shearwater eCCR controller
Type of dive Exploration Dive
Depth of accident 52m
Root Cause Using Fault Tree Human Error
Disabling Injury Hypercapnia
Key information received on accident
Two Chinese technical divers using CCR did not surface after exploring the underwater ancient Great Wall in Panjiakou, Hebei Province, China. The exploring project is one of GUE Project Baseline. Divers were not following GUE Protocol. Dive template of 60min at 60m for 3.7hr RT in 6'C water, understood to a bail out plan. Actual dive 102 minutes to LOC, of which 53 to 55 minutes bottom time, max depth 55.4m with buddy at up to 59.8m, in 6C water. After the loss of her buddy with the main bail out gas 77 minutes into the dive, she continued to decompress until at 100 minutes run time she bolted to the surface while still having a heavy decompression obligation due to aspects early in the dive and from the profile. Diver 43kg hence low metabolism. Disabling injury and cause of death was pulmonary embolism. Dive profile was beyond the known and published capabilities of the scrubber. The BOV was a pre-CE BOV which had too high a WOB to support a diver suffering hypercapnia. Diver bailed to separate OC for ascent but little gas used as LOC occurred. Autopsy found evidence of pulmonary embolism. Some data withheld from publication due to confidentiality.
Comments or Discussion in arriving at most plausible cause, addition to use of the Fault Tree.
Most probable root cause is hypercapnia. Cause of diver bolting to the surface is hypercapnia. Disabling injury is LOC due to arterial gas embolism. Full details of dive not published at family's request.
Training implications
The scrubber duration published by JJ CCR:
http://www.jj-ccr.com/the-jj-ccr/scrubber-unit.aspx In this manufacturer's data, the duration is 40 minutes at 40m depth. At 50m, the duration will reduce substantially - not just by 1/6th (the difference of the two absolute depths) and the duration to the point of rapid ascent was considerably longer than 40 minutes. On this data alone, the dive profile exceeds the manufacturer's stated scrubber duration, even at 40m. The JJ-CCR scrubber results were produced by ANSTI, and the dosing was less than 1.6lpm of CO2 at 0C, so the manufacturer's data is for a metabolic rate of between 1.4 and 1.5lpm of CO2 production - this can be generated for a long duration if a diver is working hard. The diver had a lower body mass than her male buddy and her dive involved less exertion, hence she could survive longer on the scrubber than the buddy, however not enough to complete decompression. The non-CE BOV is a factor: the diver would not have been able to breathe from this while suffering hypercapnia, increasing stress and the consideration to bolt to the surface.
Design implications
JJ-CCR publish an honest statement of scrubber duration. Many others do not. Divers using similar sized scrubbers are often presented with misleading durations that involve short bottom times and long decompression profiles, or are based on low metabolic rates. Presentation of long scrubber times within the dive community may well be the factor that led the divers to believe the scrubbers were sufficient for the dive. The buddy's dive scooter failed, which would likely lead to longer bottom times as the divers combined. The BOV was a pre-CE BOV which had too high a WOB to support a diver suffering hypercapnia.
Deceased's Name Chinese Male
Rebreather involved JJ-CCR, DSV
Electronics fitted to rebreather for PPo2 Monitoring or Control Shearwater eCCR controller
Type of dive Exploration Dive
Depth of accident 52m
Root Cause Using Fault Tree Human Error
Disabling Injury Hypercapnia
Key information received on accident
Two Chinese technical divers using CCR did not surface after exploring the underwater ancient Great Wall in Panjiakou, Hebei Province, China. The exploring project is one of GUE Project Baseline, however divers were not GUE trained. Dive template of 60min at 60m for 3.7hr RT in 6'C water, understood to be a bail out plan. Actual dive 77 minutes duration to LOC, of which 54 minutes bottom time, max depth 59.8m in 6C water. Diver 80kg hence typical male metabolism and CO2 production in the circumstances of the dive. Heavier than planned exertion after a scooter failure and with two 11L stages. Dive on video. Dive profile was beyond the known and published capabilities of the scrubber. Dive computers logged depth and PPO2: PPO2 normal. Bailed out onto OC, and emptied both stages rapidly. Cause of death was drowning. Some data withheld from publication due to confidentiality.
Comments or Discussion in arriving at most plausible cause, addition to use of the Fault Tree.
Accident Investigation conducted at behest of friends and family. Root cause was hypercapnia. Causing of death was drowning. Full details of dive not published at family's request.
Training Implications
The scrubber duration published by JJ CCR:
http://www.jj-ccr.com/the-jj-ccr/scrubber-unit.aspx In this manufacturer's data, the duration is 40 minutes at 40m depth. At 50m, the duration will reduce substantially - not just by 1/6th (the difference of the two absolute depths). On this data alone, the dive profile exceeds the manufacturer's stated scrubber duration, even at 40m. The JJ-CCR scrubber results were produced by ANSTI, and the dosing was less than 1.6lpm of CO2 at 0C, so the manufacturer's data is for a metabolic rate of between 1.4 and 1.5lpm of CO2 production - this can be generated for a long duration if a diver is working hard. Note the amount of OC gas used (two 11L stages): a person suffering hypercapnia has a very high RMV and requires a considerable volume of bail out gas – divers must bail out as soon as hypercapnia symptoms are apparent, as if left for later then it may be impossible to get enough gas.
Design implications
JJ-CCR publish an honest statement of scrubber duration. Many others do not. Divers using similar sized scrubbers are often presented with misleading durations that involve short bottom times and long decompression profiles, or are based on low metabolic rates. Presentation of long scrubber times within the dive community may well be the factor that led the divers to believe the scrubbers were sufficient for the dive. The scooter failed, leading to heavier exertion and would likely lead to longer bottom times, however the dive was within the template.
