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Union Carbide India Ltd, Bhopal, India. 3rd December 1984

Accident summary

In the early hours of 3 December 1984 a relief valve on a storage tank containing highly toxic methyl isocyanate (MIC) lifted. A cloud of MIC gas was released which drifted onto nearby housing.

Prior to this, at 23.00 hrs on 2 December, an operator noticed the pressure inside the storage tank to be higher than normal but not outside the working pressure of the tank. At the same time a MIC leak was reported near the vent gas scrubber (VGS). At 00.15hrs a MIC release in the process area was reported. The pressure inside the storage tank was rising rapidly so the operator went outside to the tank. Rumbling sounds were heard from the tank and a screeching noise from the safety valve. Radiated heat could also be felt from the tank.

Attempts were made to switch on the VGS but this was not in operational mode.

Approximately 2,000 people died within a short period and tens of thousands were injured, overwhelming the emergency services. This was further compounded by the fact that the hospitals were unaware as to which gas was involved or what its effects were. The exact numbers of dead and injured are uncertain, as people have continued to die of the effects over a period of years.

The severity of this accident makes it the worst recorded within the chemical industry.

Failings in technical measures


FP Lees, ‘Loss prevention in the process industries – Hazard identification, assessment and control’, Volume 3, Appendix 5, Butterworth Heinemann, ISBN 0 7506 1547 8, 1996.