UCC’s own brochure on MIC had clearly stated that:
(1) “Methyl isocyanate (MIC) is reactive, toxic, volatile, and flammable” (p.1);
(2) it “is a hazardous material by all means of contact”;
(3) it “is a poison by inhalation”;
(4) it “should also be regarded as an oral and contact poison”; and
(5) “Stringent precautions must be observed to eliminate any possibility of human contact with methyl isocyanate.” (p.25)
The extremely toxic and reactive nature of MIC required that the storage system was safe and its related instrumentation and control systems were of high reliability. The instructions in the said brochure in this regard specifically said:
“Maintain a tanks’ temperature below 15°C (about 60oF) and preferably at about 0°C (32°F). Equip a storage tank with dual temperature indicators that will sound an alarm and flash warning lights if the temperature of the stored materials rises abnormally.” (p.7)
It also said: “Keep the storage system and transfer lines free of contaminants.”(p.8) This was because: “Trace quantities of the contaminants are sufficient to initiate reaction…. The heat evolved can generate a reaction of explosive violence. Water reacts exothermically to produce heat and carbon dioxide.” (p.9) Therefore,
“…bulk systems must be maintained at low temperature. With bulk systems, contamination is more likely than with tightly sealed drums. The potential loss is much greater, too. The low temperature in a bulk system will not eliminate the possibility of a violent reaction, if contamination occurs. It will, however, increase the time available for detection of the reaction and safe disposal of the materials before the reaction rate reaches a dangerous speed.” (p.10) 
UCIL’s “Operating Manual Part-I – Methyl Isocyanate Unit” had also issued a fore-warning as follows:
“…it must be foremost in everybody’s mind that there is a probability of injury or accident round the corner. But these can be avoided if all are safety conscious and follow safety procedures strictly. Safety is our prime need. All chemicals like MIC, phosgene, HCl, CO, Chlorine, MMA, chloroform and caustic soda etc. however hazardous they are, can be handled safely by knowing the correct procedure. There is a correct way of handling them and there is “No Short Cut”. Any carelessness in operation will endanger you, your colleagues and everybody around you.” 
UCIL’s “Operating Manual Part-II – Methyl Isocyanate Unit” had stipulated stern safety norms for maintenance of “MIC Storage Tanks” as follows:
“(iv) Keep circulation of storage tanks contents continuously ‘ON’ through the refrigeration unit and maintain tank temperature below 5ºC. Set temperature instrument (TIA) to sound alarm at 11ºC.
(v) Watch for differential temperature instrument (RDRA) provided in the MIC make line. It will sound an alarm if the temperature difference between the probe provided near the storage tank and the probe near the MRS condenser, in MIC make line, exceeds 5ºC. Immediately divert the MIC make to the dump tank and take corrective action after establishing the reason….” 
However, contrary to the stringent requirements of keeping the MIC storage tank definitely below 5ºC, it is an admitted fact that over 85 tonnes of MIC had been stored under ambient temperature (i.e., above 15ºC and up to 40ºC) with the full knowledge of the concerned UCC/UCIL officials from June 1984 onwards. Therefore, it is amply evident that all the accused officials of UCC and UCIL had prior knowledge of the disastrous consequences of shutting off the refrigeration system in complete violation of stipulated safety norms; they cannot now pretend that they did not know that those safety norms had to be “stringently” observed.
The instructions in the said UCC’s brochure and UCIL’s safety manuals were unambiguous about the stringent safety precautions that were to be observed while storing and handling MIC. But, neither were adequate steps taken to prevent entry of foreign bodies (which act as reactive agents or as catalyst that trigger highly volatile reactions) into the MIC storage tanks nor were appropriate instrumentation systems and personnel in place to monitor and forewarn about any unusual pressure and temperature build-up in the storage tanks at the Bhopal plant. Moreover, the three critical safety systems – i.e., (1) the refrigeration unit (for keeping MIC “preferably at about 0°C (32°F)” so as to retard volatility); (2) the vent gas scrubber unit (VGS, for neutralising any escaping toxic material by chemical treatment); and (3) the flare tower (for burning off toxic gases in case of any accidental release) – had all been either shut off or were under repair at the time of the disaster. No stand-by systems were in place for use during breakdown or routine maintenance. These facts point to criminal negligence on the part of the concerned UCC/UCIL officials who did not take adequate precautions to prevent the disaster despite having prior knowledge of not only the highly hazardous nature of MIC but also that the pesticide factory was situated very close to thickly populated human habitations. UCC itself confirmed most of these facts in its Report, which was prepared by UCC’s Investigation Team that had visited Bhopal soon after the disaster to inquire into the circumstances that led to the gas leak.
Image: Maude Dorr
Part 2 of a serialised article by N. D. Jayaprakash