December, 1984

198403DecAll DayBhopal 1984 - Incident SummaryMethyl isocyanate storage tank temperature runaway Origin: IChemE SLP Lessons:Asset integrity,Commitment & Culture,Emergency Preparedness,Management of Change,Risk AssessmentLanguage:EN TagsAccountability,Bhopal,Control,Flare Systems,Isolation,MIC,MoC,Runaway,Sabotage,Scrubber,Tank,Toxic,Training


Carbaryl (an insecticide) was being manufactured by reacting methylamine with phosgene to make a methyl isocyanate intermediate product which then reacted with 1-napthol. On the morning of the incident, an exothermic reaction occurred in the nitrogen-purged stainless steel methyl isocyanate intermediate storage tank. The temperature and the pressure at the tank continued to rise until 40 tonnes of highly toxic vapours, including methyl isocyanate (MIC) and hydrogen cyanide (HCN) were released to atmosphere via the pressure relief system. The official death toll was 2153 but some unofficial estimates were > 16,00 (uncertain due to unknown population of shanty town adjacent to the plant). The plant never restarted.

Basic Cause:
Runaway chemical reaction caused by water ingress to the MIC intermediate storage tank (isolatrion error or sabotage?)


IChemE SLPSafety & Loss Prevention Special Interest Group