Compressed air rather than oxygen supplied to divers

What happened

Several divers were affected and two divers became ill when compressed air rather than oxygen was supplied to them by mistake on their BIBS (Built in Breathing System). The error caused two lymphatic/skin decompression illnesses and incorrect decompression profile for several other divers.

What went right?

• Dive and project team reacted appropriately when decompression illness was suspected;
• All emergency procedures were followed;
• Once the root cause was identified and understood all work stopped and investigation and controls were conducted, and the dive and project team took the correct and required actions.

What went wrong

• The gas supplier’s agent did not have sufficient control:
  • The wrong kind of gas was delivered – there was no check of the gas quad before it was dispatched;
  • The gas quad had incorrect labelling and colour code and was similar to the other 100% oxygen quads stored at the mobilization site;
  • The threads on the quad piping system containing compressed air were compatible with the approved medical oxygen regulator.
• The oxygen fraction (FO₂) of the third-party gas quad was not checked by the diving contractor upon delivery to site;
• The gas quad fixed pressure manometer (pressure reading) was checked at the site of the quad on 92 occasions by 21 individuals, but no one noticed the difference of the air quad from an oxygen quad;
• The dive system had online gas analysers on all gas types and delivery systems except for the BIBS gas supply line to chamber;
• The team investigating the first incident did not consider the possibility of inappropriate breathing gas. This failed to identify the underlying cause and allowed a second incident to occur.

Lessons and actions

• Better control of supplied diving gases;
• More thorough auditing of diving gas supply chain;
• Improve competence and training in two areas: dive technicians’ labelling of gas, and management site investigation;
• Ensure diving gas supply and analysis equipment is fit for purpose;
• Company added new verification requirements, based on the incident, including:
  • Can the BIBS supply be analysed on the chamber panel;
  • Does the competence scheme capture technical know-how of gas management and verification?
  • Do investigation lead/ technical advisors hold formal training in investigation?
  • Ensure regular and thorough audit of third party gas suppliers;
  • Ensure company procedures and routines comply with IMCA guidance on gas management and control

Members may wish to refer to:

• Failure to follow gas quad procedure
• Substandard nitrogen quads delivered to shipyard
• Helium gas quad – gas variances across quadrants
• High potential near-miss: Poor O₂ content in supplied air – diver temporarily lost consciousness