Investigation report by Transport Safety Investigation Bureau Ministry of Transport Singapore identifies the reason for fire on board Maersk Honam as thermal decomposition of Sodium Dichloroisocyanurate Dihydrate classified as class 9 UN 3077, ENVIRONMENTALLY HAZARDOUS SUBSTANCE, SOLID, N.O.S..

Dichloroisocyanuric acid, dry or dichloroisocyanuric acid salts are classified under class 5.1, oxidizing substances, in IMDG Code, assigned to UN 2465.

Special provision 135 of IMDG Code excludes dihydrated sodium salt of dichloroisocyanuric acid from inclusion in class 5.1 due to lower chorine level and lesser oxidizing properties.

The investigation find merit in relooking special provision 135 of IMDG Code and in the interim shippers to ensure full compliance to IMDG Code, the product, dihydrated sodium salt of dichloroisocyanuric acid, is stable and carriers to adopt similar policy as put forth for calcium hypochlorite by CINS, stow the boxes on weather deck away from direct sunlight.

Another observation by the investigating team was about the format of safety data sheet submitted electronically. It says most SDS were scanned documents which prevents electronic reading using keyword searches.