Calcium hypochlorite

Calcium hypochlorite (Ca[OCl]2) is unique in terms of its dangerousness and the losses it causes in maritime container transport. Ca(OCl)2 is believed to have caused the explosions and fires in at least three of the cases mentioned above.

Classed as an oxidising substance (IMDG Code, Class 5.1) this chemical is used in the production of bleaching powder, as a disinfectant for swimming pools, and in the treatment of drinking water. Due to its composition, calcium hypochlorite must be classified as follows during transportation:

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  UN 1748 (anhydrous calcium hypochlorite),
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  UN 2880 (hydrated calcium hypochlorite), and
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  UN 2208 (bleaching powder).

What makes Ca(OCl)2 so dangerous is the fact that it can react with itself at high temperatures. The capacity for such a reaction increases with the size of the packing unit. Depending on the exact chemical composition involved, the chemical may become instable at temperatures like those that can occur in the tropics or in the hold over heated fuel tanks in a vessel’s double hull.

Violent reactions may also occur if the chemical comes into contact with other substances, for example, if the packaging is inadequate or damaged. For these reasons, Ca(OCl)2 with the UN classification numbers stated above may only be stowed on deck and at a sufficient distance from the crew’s quarters. It is also to be protected against the sun’s rays.