1 The Sub-Committee on Dangerous Goods, Solid
Cargoes and Containers (DSC), at its ninth session (27 September to
1 October 2004), considered an investigation report submitted by Italy
on three different ships carrying zinc ingots. Inside the holds of
the above ships arsine was accumulated in high concentrations. Four
crew members felt ill after entering into cargo holds and one of the
crew members died in the local hospital.
Following investigations, the cargo present on board of the
above ships was revealed to be Zinc Ingots 98.5% pure or less GOB
(good ordinary brand).
2 The Italian Maritime Administration has issued
a safety guideline which requires a special atmosphere's test in all
cargo holds on board ships loaded with zinc ingots. These tests are
carried out before opening cargo hatches, by a competent chemist,
in order to guarantee that the atmosphere inside the holds is safe
for entry/work during opening and unloading operations, taking into
account the presence of toxic or flammable gases or other hazards.
3 The Sub-Committee's attention was drawn to the
conclusion of the investigation that:
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.1 the first test on board of the first ship revealed
a concentration of arsine of 10 ppm. Such tests had been carried out
around a week after the accident and after the holds of the ship had
been left open for some time. This supposes that the concentration
of arsine in the atmosphere of the closed holds at the time of entry
of the crew members was much higher than the 10 ppm stated above;
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.2 afterwards official sanitary reports confirmed
that the arsine (arsenic hydride: AsH3), evidently present in the
holds of the first and second ships in higher concentration in comparison
to the threshold's limit, was responsible for the death of a sailor
and the hospitalization of other crew members;
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.3 the tests on board the third ship revealed
a concentration of arsine of 3 ppm in the holds. Precautionary tests
of the port chemist avoided an incident on board this ship because
the level of concentration of arsine was also in this case, dangerous
to the human health;
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.4 the above report shows two common characteristics:
the presence of arsine and fresh water;
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.5 the development of arsine was possibly due
to the presence of zinc ash not completely removed from the surface
of ingots;
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.6 tests carried out on board other ships carrying
only zinc ingots of 99.995% purity or more SHG (special high grade)
had not revealed any detectable concentration of arsine inside the
cargo holds.
4 It is therefore recommended that, in transporting
zinc ingots 98.5% pure or less GOB (good ordinary brand), particular
attention should be paid to the following:
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.1 wet cargo should not be loaded and weathertightness
of hatches should be ensured;
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.2 the cargo should be kept dry and not be handled
during precipitation;
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.3 suitable gas detectors for the measurements
of hydrogen and arsine and, at least, two sets of self-contained breathing
apparatus, additional to those required by regulation II-2/10.10 of the 1974 SOLAS Convention, as amended,
should be provided;
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.4 continuous mechanical ventilation is required.
Ventilation should be such that any escaping gases cannot reach living
quarters on or under deck;
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.5 entry into the holds without wearing the self-contained
breathing apparatus must not be permitted until ventilation of the
holds has been carried out and after tests reveal no detectable concentration
of arsine/flammable gases inside the holds;
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.6 tests must be carried out before opening cargo
hatches, by a competent person, in order to guarantee that the atmosphere
inside the holds is safe for entry/work during opening and unloading
operations, taking into account the presence of toxic or flammable
gases or other hazards; and
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.7 possible ignition sources as well as hotwork,
burning, smoking, electrical sparking should be eliminated during
handling and transport.
5 Member Governments are invited to bring the
above information to the attention of shipowners, ship operators,
companies, shipmasters, shippers and all other parties concerned,
requesting that appropriate action be taken when transporting such
cargoes.