What caused the gas leak?
Shortly after the gas release, Union Carbide launched an aggressive effort to identify the cause. An initial investigation by Union Carbide experts showed that a large volume of water had apparently been introduced into the methylisocyanate (MIC) tank. This caused a chemical reaction that forced the pressure release valve to open and allowed the gas to leak. A committee of experts working on behalf of the Indian government conducted its own investigation and reached the same conclusion. An independent investigation by engineering consulting firm Arthur D. Little determined that the water could only have been introduced into the tank deliberately, since process safety systems — in place and operational — would have prevented water from entering the tank by accident.
