Hazardous and Noxious Substances Spill Incidents

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On this database it is collected information on the fate and weathering of hazardous and noxious substances (HNS) accidentally spilt at the sea around the world. It gathers and systematizes existing information to assist stakeholders involved in spill preparedness and response, and builds return of experience datasheets for the chemicals involved. It will facilitate the incorporation of lessons from past incidents on the decision process to improve preparedness.

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Mediterranean Sea



HNS Spilt

Calcium hypochloriteSolid


Amount Spilt (T)Unknown

CAS Number7778-54-3


Physical Behaviour (SEBC code)


Pollution Category (MARPOL Annex 2)


Class according to IMDG code


Subsidiary Risk Class according to IMDG code

Classification as Marine Pollutant


HNS Classification (2010 HNS Convention)

Fate and weathering facts observed/reported

This product had self-combusted, possibly as a result of impurities, either due to the manufacturing process of such bleaching powder or as a result of contamination during transport. The chemical readily decomposes to release chlorine and oxygen. Some drums of calcium hypochlorite had a propensity to undergo a self-accelerating decomposition reaction that concluded with an explosion releasing large clouds of thick white “smoke”. The International Group of P&I Clubs paid a study were it was found that self-accelerating decomposition in a 40ft container could start at temperatures in the order of 37oC, a temperature well within the range of temperatures that could be expected during ocean voyages. This compound is of category X if concentration is > 50% or Y if it is bellow < 50%.

Material Safety Data Sheets (MSDS)