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First aid injury: Thermos cup exploded after being in hyperbaric environment

A member has reported an incident in which a brushed aluminium ‘Thermos’ style cup exploded after being taken out of a hyperbaric environment. The incident occurred when the cup – which had been in Sat at -256 fsw with the diver – was placed in the medical airlock and brought to the surface. Once at surface pressure the Assistant Life Support Technician (ALST) removed the cup and placed it under his arm, whereupon a violent separation of the cup from its plastic base occurred. The ALST suffered minor bruising and the cup was destroyed. Immediate medical attention was given, and a proper and timely notification to the appropriate authorities was made. The remains of the cup were retained for investigation.

Our member’s investigation noted that the diver had considered that there was no risk of a pressure differential as the interface between the metal and the plastic base on the cup was of insufficient strength to allow a pressure differential to form.

Our member took the following actions:

  • Advised divers in saturation what had happened;
  • Asked them to check carefully for additional objects of a potentially hazardous nature.

Our member made the following recommendations:

  • Allow this style of cup or vessel in the saturation chambers only if drilled to prevent pressure build up;
  • Add non-venting thermal vessels to the list of items forbidden for use in saturation chambers.
Thermos cup after explosion
Thermos cup after explosion – bottom of cup blew out
Thermos cup after explosion
Thermos cup after explosion – top view
Thermos cup after explosion
Thermos cup after explosion – plastic base of the cup blew out due to trapper pressure
Thermos cup after explosion
Thermos cup after explosion – bottom end minus the plastic that blew out


Members may wish to refer to the following similar incident:

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