In SwedishFinal report on dangerous atmospheres around wood cargoes
Too little oxygen and high levels of carbon dioxide. The research project shows that potentially lethal atmospheres are created around wood cargoes, which have caused a number of deaths.
The staircase where two seamen died when the ship was moored at Timrå in May 2007
During the last four years, five people have died and others have been injured on Swedish ships with cargoes of wood products or on foreign ships in Swedish waters. The deaths occurred in staircases and stores next to cargo holds, and it is in these spaces that researchers made their measurements. Last spring the first of two reports on dangerous atmospheres around cargoes of wood products was published (see San News no. 2 2008). It showed that wood pellets can generate high levels of carbon monoxidea short time period.
– A few breaths can be enough to make you unconscious and within a few minutes you can be dead. It is like internal suffocation, says Urban Svedberg at the Occupational and Environment Medicine Clinic at Sundsvall hospital.
Warmth increases the risks
The second part of the research project was finished in June this year and looked at timber and wood chips. The results show that these products can also create lethal atmospheres with low oxygen levels and large quantities of carbon dioxide. Out of 76 staircases and stores checked, 71 had a lower oxygen content than the normal 20.9%. One third had potentially lethal levels of 6% or less, and every fifth sample contained no oxygen at all.
– If you go down into a room with low oxygen levels, you may not realise the danger for a while. By then it is not certain that you have the time to get out before it is too late, says Urban Svedberg.
The following measures can reduce the risk of such accidents, according to Urban Svedberg:
- Hang a chain or rope over open manholes next to holds, and put up a clear warning sign.
- Put up warning signs on the inside and outside of doors and manholes so that they are visible whether the door is open or closed.
- Avoid storing materials in spaces next to holds so that people do not have to go in there.
- Keep spaces next to holds locked during sea passages and have one person responsible for the key.
- Installs pipes in shafts leading to the holds so that measurements of oxygen levels and other gases can take place safely from the deck.
- Ventilate staircases properly. It can take up to 24 hours before the air is fully restored.
- Ensure that measuring equipment onboard is adapted to the cargo and that it is working properly. Everybody onboard must have the knowledge required to use it.
The dangerous atmosphere is generated by micro-organisms that thrive on wood. They consume oxygen and produce carbon dioxide, and are most active on newly felled timber. The biological process is influenced by the temperature and during the warmer summer months these dangerous atmospheres are generated more quickly than during the winter.
– But there are no safe seasons and accidents have occurred during the winter, too. The process is just a little slower when it is cold, explains Urban Svedberg.
Linda Sundgren
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