337 - 12/03 - Problems with Thiourea Dioxide - Worldwide

Thiourea dioxide or formamidine sulfinic acid is a white to pale yellow colourless crystalline powder used as a reductive agent in the paper industry and a bleaching agent in the textile industry. It can be produced by reacting hydrogen peroxide with thiourea.In the period 1996/97 there were several incidents related to the decomposition of thiourea dioxide. In one incident in the Far East 400 workers were evacuated from a marine terminal and several workers were placed in hospital. At that time the chemical was not included in the IMO Dangerous Goods Code.When exposed to heat the chemical will rapidly decompose, a reaction which may be catalysed by metal salts. This decomposition is accompanied by the release of toxic and corrosive gases including sulphur oxides, ammonia, carbon monoxide, nitrogen oxides, hydrogen sulphide etc. Sulphur oxides can further react with moisture to form acid conditions. The acid may then attack neighbouring cargo in one instance destroying a cargo of computer equipment.


Thomas Miller