This Safety Alert is issued by the Bahamas Maritime Authority (BMA) to share lessons to be learned on the safe handling and storage of dry ice. It is based on the findings of a preliminary investigation into the death of a service technician.
A Bahamas flagged drill ship was in an extended maintenance period. Scheduled work included disassembly of a component of the ship’s drilling equipment. To complete the work, a subcontractor needed 300kg of dry ice which was supplied in 20 unmarked insulated boxes. The boxes were received onboard three days before work was started and stored in a cold room.
On the evening before the work was to be carried out, a service technician was found, sat down and apparently frozen, in the cold room. There were no signs of disturbance or injury. The emergency door release and entrapment alarm were confirmed to be working and had not been activated. The cold room’s lighting was permanently on and functioning.
Other members of the crew had been in the cold room about an hour earlier. Neither they, nor the responders, reported any symptoms or ill health. The ship’s doctor’s initial diagnosis was that the death was due to natural causes. Results of the postmortem are outstanding.
Safety Factors
Dry ice is the common term for solid carbon dioxide (CO2). CO2 solidifies at approximately -78°C. At temperatures warmer than -78°C it turns directly from a solid into a gas (a process known as sublimation). Dry ice must be packaged in non-airtight containers to avoid pressure build up as carbon dioxide gas is produced. Carbon dioxide gas is heavier than air.
Carbon dioxide rich environments do not support human life. Concentrations above 0.5% are dangerous and above 4% can prove fatal. CO2 is odourless and does not cause irritation, resulting in poor warning properties.
A small amount of dry ice produces a large volume of gas, at an approximate ratio of 1:850. 300kg of dry ice could produce approximately 162m3 of carbon dioxide gas if allowed to sublimate at atmospheric pressure. Due to the sublimation process it is imperative that dry ice is stored in a well ventilated area.
A study conducted by the US Federal Aviation Administration1 to assess the dangers of carrying dry ice in aircraft identified that dry ice sublimates at a rate of 1% per hour. This rate will vary depending on the packaging, dry ice particle size, surrounding temperature, and atmospheric pressure.
The dry ice was procured without an assessment of the risk it could pose or an appropriate plan for its storage. The insulated boxes were not marked to highlight the danger they posed or the need to be stored in a well ventilated area.
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