The first leak of MIC was noticed on 02.12.1984 at about 23.30 hours in the MIC structure area near the VGS. The operators on the ground level in this area felt the presence of MIC in the atmosphere due to irritation of their eyes. The operators who informed the plant superintendent and the supervisor that there was an MIC leak were advised to spray water around the point of leakage. Around 00.15 hours on 03.12.1984, the rupture disc of the tank that was set at 40 psig burst under intense pressure and the Safety Relief Valve (SRV) opened. Soon the field operator noticed gaseous cloud coming out from the stack. The siren was reportedly sounded around 00.30 hours and the plant personnel were alerted about the gas leak. From around 01.00 hours, water was sprayed to neutralize the gases but apparently it did not reach the top of the stack from where the gases were coming out. Around 03.00 hours, the SRV of Tank 610 is reported to have sat back, which stopped the further flow of gas through the stack. The maximum temperature and pressure that the mixture underwent in the tank during the violent reactions had a direct bearing on the types and toxicity of the reaction products that finally came out of the tank. According to the Varadarajan Committee, “…the mechanical examination of the tank indicates that the pressures may have reached 11 to 13 kg/cm2g with the corresponding temperatures in the range of 200 to 350ºC.” 
The amount and types of materials forced out of the tank have not been determined exactly. According to the UCC Investigation team:
“However, based on the heats of reaction, about 40 percent of the MIC reacting would release enough heat to raise the temperature of the tank and vaporize the remaining 60 percent of the MIC.”
“In order to discharge most of the contents of the tank within two hours, the pressure had to average 180 psig. At these conditions, material would be discharged at a rate of 40,000 pounds per hour: 29,000 per hour of vapor and 11,000 pounds of solid/liquid mixture. Approximately 54,000 pounds of unreacted MIC left Tank 610 together with approximately 26,000 pounds of reaction products.”
Neither the senior managers of UCC nor of the UCIL can by no stretch of imagination claim that they were unaware of the disastrous consequences of criminal mismanagement. These officials had prior knowledge that MIC is an extremely lethal material and that any release of the toxic chemical into the atmosphere would have grievous impact on life systems and the environment of Bhopal. Its properties were such that “on thermal decomposition, MIC could produce hydrogen cyanide …carbon monoxide…”, i.e., its byproducts are also highly poisonous. Their failure to formulate in advance an emergency preparedness plan and an evacuation plan for the population of Bhopal only compounded the problem. Therefore, there is ample prima facie evidence to hold the management of UCC, UCE and UCIL and the three companies guilty of criminal acts that caused the catastrophe and to prosecute them under Section 304 Part II (culpable homicide not amounting to murder) of the Indian Penal Code through imprisonment and by imposing punitive fines.
Part 8 of a serialised article by N. D. Jayaprakash