The Bhopal gas strategy of December 1984 will forever remain a blight in the history of process safety and engineers will continue to learn and re-learn the lessons associated with the notorious gas leak. Many hypothetical scenarios and models have discussed prevention strategies, and arguably, the most effective of these is the Incident Command System (ICS).

In general, a typical incident command system (ICS) takes three key components into account:

• Prevention: identification of credible scenarios and operation procedures as well as safety measures (in this case it would be the toxicity of MIC).

• Communication: Rapid communication between management, safety officers, site emergency responders, neighboring communities, and police officials (there was a lack of communication between employees and management at the plant).

• Mitigation: Adequate and transparent sharing of information and cooperation with external services for mitigation of damage (the existing safety protocols at the plant were poorly implemented or were not followed due to outright human negligence or error).

Corporate and public policies related to the use of methyl isocyanate (MIC) at the plant should have been communicated to employees, government officials, and civilians alike. It is unclear what processes led to the water reaching the highly reactive toxic chemical intermediate, but the most widely accepted explanation suggests that one of the overflow systems from the filter was obstructed.

A quick sequence of events that led to the disaster reveals that the catalyst of the leak was the reaction of water with MIC. There would have been no viable pathway for the water to flow into the vent system if proper safety procedures had been followed. This could have been avoided if safety engineers had installed a slip bind to create a seal between connected pipes.

What's especially concerning is that operators ignored the pressure gauges to the tank once the water reached the storage tank containing over 42 tons of MIC. They did not have a reliable means of measuring the tank temperature. Furthermore, operators were required to maintain the pressure at a certain level to prevent such a situation from occurring. Even more concerning is the fact that there was an undetected gas leak that connected the tank to the plant's main pipes.

For obvious reasons, if gas can leak out, then water can make its way in (if there is sufficiently high pressure).

One preventive mechanism was to keep the temperature of the tank cool to prevent a thermal runaway condition. Unfortunately, this was not to be because the refrigeration system had been turned off several months ago. This facilitated a thermal runaway reaction and led to hot MIC vapors escaping through the faulty gas scrubber, which was designed to deal with waste gases from the plant.

Once this series of events was completed, nothing could be done to further stop the gas leak. It should be noted that a competent Incident Command System (ICS) could have prevented this gas leak by creating safety measures including:

• installation of a safety bind

• taking pressure readings more seriously

• taking temperature measurements of the tank

• maintaining the required pressure within the tank

• installing an adequate refrigeration system

• having a fully functional vent gas scrubber

• having a fully functional flare system

• a tall enough water curtain

Even one of these safety measures could have prevented the thermal runaway condition in its track and prevented the loss of lives and capital.

Defining a Competent Emergency Response System

Corporate management at the Bhopal plant displayed gross negligence in defining an adequate emergency response system which could have served as the last layer of defense to minimize the consequences of the deadly gas leak. A competent Incident Command System defines actions that should take place before, during, and after an incident. These include:

Before the Bhopal leak - Deployment of treatment methods to identify potential airborne toxic emissions, and airborne hazards. A knockdown tank should have been installed to direct discharged MIC to the flare tower, but no such safety mechanism was in place.

During the Bhopal leak - In the absence of a well-defined safety system in place, the operators and employees were scrambling to do damage control. Their ad hoc response was inadequate and prone to errors (mostly brought about by the severe stress of the situation). It was clear that the rational decision-making capabilities of the operators were severely limited due to the highly stressful situation they found themselves in.

After the Bhopal leak - The alarms systems were not loud enough and failed to be heard outside the factory. Furthermore, there were no evacuation routes, which means that those who were trapped had nowhere to go. As a result, information related to evacuation was delivered too little too late to authorities (including hospital staff and police officials). It was the responsibility of the management to create detailed emergency plans for relevant authorities to initiate rescue efforts in the event of a disaster.

Lessons Learnt from the Bhopal Gas Tragedy - Creating a Prevention System Based on ICS

The primary objective of hazardous installation is the prevention of accidents that could cause harm to human health and the environment. A quick analysis of the Bhopal gas leak incident reveals that all human-initiated catastrophes were a result of failure from management. Most prevention mechanisms are poorly handled because production or financial targets are prioritized over safety protocols (despite the risk of human life).

That said, it is not easy to take stock of undesirable events in a complex system such as the Bhopal plant. This requires all safety officers, corporate officials, and government officials to evaluate safety processes and ensure very high compliance with regulations.

In this regard, safety officers should have established systems for

• identification and notification of any leaks of MIC

• constantly monitoring changes in temperature and pressure of the MIC tank

• ensuring that there is adequate reporting and investigations of any potential leaks

Furthermore, management should ensure that safety is not compromised during stressful periods at the plant, such as when there is an economic slowdown or staffing problems.

Emergency Preparedness

Public authorities, as described above, should be appraised of emergency preparedness programs as they relate to accidents involving the leak of MIC. The role and responsibilities of internal and external services (that are expected to be involved in emergency activities) should be properly defined in emergency plans (including management, employees, and police officials).

First responders (including police, fire, and medical personnel) should receive training and education to take appropriate actions to minimize their exposure to hazardous substances.

Management should have ensured that everyone employed at the site receives appropriate training and education on handling hazardous substances and procedures to follow to avoid accidents from occurring, and which actions to take, should an accident occur, in order to minimize adverse health consequences for individuals available at the site.

The site should be regularly stocked with adequate antidotes, as well as emergency supplies necessary for the treatment of individuals who may have been injured by exposure to hazardous substances. Nearby hospital facilities should developsystems for handling a large number of expected patients at one time.

As part of the emergency preparedness process, communicationbetween all stakeholders should be examined. This includes the parties that need information, and the types of information they need access to, and the parties that are responsible for sharing the necessary information.

During the Emergency

During the emergency, all personnel at the plant should have become part of the overall response team and part of the information chain, to exchange relevant information as needed. Systems at the plant should have been put in place to collect and disseminate available information to personnel and other parties as the state of the emergency progressed, including medicalinformation.

The on-site safety officer should make calculated decisions on the mediate actions that should be taken, including actions intended to limit exposure to the MIC leak, based on preliminary information concerning the plant. Health and medical personnel should provide assistance upon request, based on the decisions taken by the safety officer.

Arrangements should have been made of first aid and other medical treatment outside the factory. Hospitals and other treatment facilities should put their emergency plans into effect once they have been informed of the possibility of patientsarriving after the leak of MIC.

Human Error Prediction

The Bhopal gas leak was attributable to several human errors occurring in succession in the lead-up to the disaster. These human errors could have been addressed by quantitative assessment of error production conditions (EPC) to varying degrees. Each factor could of the EPC could be assigned a human error probability (HEP).

For instance, before operators were required to monitor the pressure systems of the MIC tank, the operation should have gone through the human error assessment and reduction technique (HEART) to assess the likelihood of human error. This could have allowed management to formulate the most effective error mitigation strategies by pinpointing the factors that could lead to errors (or disasters).