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High CO2 in Diver Breathing Gas.

Country: UK - Europe

Location: OFFSHORE : Specialist vessel eg diving, construction, survey

Incident Date: 23 October 2016   Time: ---

Type of Activity: Diving, subsea, ROV

Type of Injury: Other

Function: Production

Divers experienced breathing difficulties, symptoms of agitation, restricted breathing and headaches indicated high levels of CO2.

Divers reported feeling better once the divers reclaim gas system was isolated and they had switched to open circuit breathing.

Following gathering of facts and assessments of potential consequences the case was reported to the UK HSE as a RIDDOR on 28/10/16.

*Regulation 13a) Failure, damaging or endangering of life support equipment, including control panels hoses and breathing apparatus which causes a significant risk of personal injury to a diver.

What Went Wrong?:

Produced CO2 was not removed by diver reclaim soda sorb towers. Divers gas reclaim towers had been allowed to saturate permitting the CO2 levels to build up in the closed circuit reclaim loop as the scrubbing agent (soda sorb) had not been replaced at an appropriate point. Replacement of soda sorb in the divers gas reclaim is based upon monitoring of reactive alarms, this is currently accepted Industry Practice. The first and last point Reclaim Analyser alarms did not sound at the expected threshold as they had been incorrectly set up and calibrated. The divers did not initially notify the diving Supervisor of breathing difficulties when they were first apparent, the symptoms experienced at the time were not prevalent enough to raise alarm. Ineffective management of Dive manuals to ensure they align with manufacturers guidelines and provide sufficient detail regarding management of analysers.

Corrective Actions and Recommendations:

Competency: Highlight safety critical roles within Contractors Assurance/Competency schemes and assess status of completion against safety critical roles.

Familiarisation: Conduct high CO2 drills during future campaigns and crew rotations. Analyser calibration values to be visible in dive control.

Assurance/Verification: Verify DS and LSS understanding and familiarity with high CO2 emergency procedures. Verify analyser calibration and set up procedures compliance. Record verification of analyser calibration and set up in appropriate logs.

Governance: Dive system operating manuals to contain manufacturers specs on analyser calibration and set up. Share lessons learned and actions fleetwide.

Safety Alert number: 280
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