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Union Carbide's failure to maintain the standards of the equipment and workforce at the plant was bad enough. However, worse was its failure to maintain even the most basic safeguards against a possible chemical leak.

The plant's safety system had three vital components. The first was the cooling system.

Methyl isocyanate (MIC), the chemical that eventually escaped from the plant, must be kept cool at all times. It was therefore stored in an underground concrete bunker, where a cooling system was installed to ensure that the temperature remained low. But the cooling system was not working in December 1984. In fact, it had not been working since the previous May, when senior management had decided to turn it off and remove the coolant.

The second element of the safety system was the vent gas scrubber. A huge, bottle-shaped vessel, this was the plant's back-up system should a poisonous gas leak occur. In theory, if toxic gases were released, they could be directed to the vent gas scrubber, which would neutralise the emissions. On the night of 2 December 1984, the vent gas scrubber was turned off for maintenance.

The third element of the system was the back-up's back-up. If the vent gas scrubber failed to neutralise emissions, they could be sent to a flare tower where the gases could be burned at a safe distance from any people. But the supposedly 'constant' flame on the flare tower at Bhopal had been out for several months.