Incident Report

2025-10-29CCR CO2 Hit Three divers in water. Diver one on CCR with problem. Diver two on CCR no problem. Diver three on open circuit no problem. Diver one entered the water with 90 minutes of stack time remaining. Stack was packed the day before and used for 90 minutes. The planned dive was 75 minutes. Within manufacturer’s recommended limits. 37 minutes into the dive the diver signalled a problem was occurring. On turning to face Diver one, Diver two found Diver one had bailed out to open circuit. Diver one was showing signs of significant distress and struggling to breathe. The team formed up and started to escort diver one back to the entrance. Divers at maximum point of open circuit ( diver three ) penetration ( 380m ) 20m depth, when incident occurred. Diver one reported an impending sense of doom and a huge desire to be breathing fresh air. Even on open circuit for the first 10 minutes breathing rate was still very high. Divers two and three escorted diver one closely on either side. Diver one struggled to stay off the floor for that time. After 15 minutes had passed diver one reported it was starting to be easier to breathe and move. Divers two and three relaxed ever so slightly. Diver one told divers two and three to F off and give him more room. A potentially good sign. For the remaining 20 minutes of the exit progress was intermittent, sometimes slow sometimes normal pace. Divers reached surface and diver two started an immediate examination of diver one. IPO was also a concern but ruled out. Post dive analysis followed, we believe a CO2 hit was the most probable cause. Diver One initially thought his computer screen had fogged up. It had not, we believe divers vision was impaired and this was the first sign that a C02 problem was occurring. An impending sense of death was reported, it was eased by holding a large rock on the floor and dive team attention. Post dive, diver one had a significant headache for several hours. A slight pressure on chest area. Possibly muscular after nearly 40 minutes of heavy breathing. SAC ( surface air consumption ) during open circuit bailout was around 57L a minute. Extremely high. On investigation of the carbon dioxide stack in the CCR it was solid pretty much throughout the material. Canister breakthrough had happened we believe at 127 minutes. Safe Canister life on this unit is rated at 180 minutes. Diver A is a moderate / heavy smoker at 20 a day. Diver A last smoked 20 minutes before the dive. Swimming distance at reasonable speed underwater is reasonably new to the diver. Mitigation Smoking appears not to have helped this incident. Possible COPD to be checked. General fitness training should be conducted by all divers. Diver A Believes a bad/terminal outcome was an extremely high possibility if solo. Dives at depth or incurring higher workloads should be started with a fresh carbon dioxide stack. Do not over use CO2 absorbent.