Incident Report

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Incident Report 2020-05-01T16:26:00+00:00

MCCR CO2 Hit

Incident Date

1970-01-01

Incident Description

A somewhat inexperienced Solo diver (60ish UK cave dives) undertook a dive in a flooded mine to create a new route to thehole-in-the-wall on the Western-Line thus bypassing a long and heavily silted section. The anticipated dive-time led to the choice of an MCCR drager rebreather for the dive that the Solo diver had constructed and subsequently dived around 50 times without incident mostly in open water. The unit was prepped the night before and an 8 litre open-circuit bail-out was taken. A single carry-in was done positive/negative pressure and O2 flow checks conducted at the water-edge and the dive commenced. Although the Solo diver was breathing heavy this was dismissed as only a short rest had been taken due to harassment by local youths at the water-edge as well as anxiety with this being the first solo dive at the site. A moderate swim was done and breathing remained laboured during line-laying. About 35-40 minutes into the dive at -23m the Solo divers breathing rate became elevated. It took the diver immense effort to control breathing long enough to bail onto open-circuit and breathing remained elevated for at least 15 minutes after swapping onto open-circuit leading to raised anxiety levels calculating if the amount of open-circuit bail-out was adequate for the exit (it was but only just). Later examination of the unit showed possible channelling but it is believed the unit was prepped without giving the counter-lungs enough space to expand and the increased work-of-breathing led to CO2 retention.

Lessons Learned

1. Prep and check equipment properly - perform full checks immediately prior to dive even if stressed by external events if counter-lungs are enclosed (back mounted) ensure they have enough room to fully expand. 2. Plan adequate bail-out to account for an elevated breathing rate during exit 3 litres of diluent may not be enough. 3. Conduct out-of-water dive activities as part of a team. 4. Dont ignore early symptoms of a problem.
Factors
Line Management Negligible
Gas Management Major
Equipment Management Major
Equipment Failure Negligible
Training Minor
Medical Negligible
Planning Negligible
Procedural Error Major
Cave Environment Minor
Weather Negligible
Other Factor Minor