The Bhopal Gas Tragedy — Part I: Process Safety Culture

The Bhopal gas tragedy stands as a stark reminder of the critical importance of process safety management. Forty years after the disaster, this article emphasizes the significance of the event and what it reveals about the prevailing process safety culture.

The Bhopal gas tragedy occurred on Dec. 3, 1984. Forty years later, this incident is still recognized as history’s worst industrial disaster (1). This article explains the significance of the Bhopal gas tragedy and why it is still relevant today.

The Bhopal disaster started inside a chemical plant in Bhopal, Madhya Pradesh, India. The factory was owned and operated jointly between the U.S. conglomerate Union Carbide Corp. (UCC) and its foreign entity, Union Carbide India Limited (UCIL). On the evening of Dec. 2, 1984, a large amount of water entered Tank 610. Tank 610 was one of two large chemical storage tanks that contained methyl isocyanate (MIC), a highly reactive and toxic intermediate ingredient used to manufacture pesticide products at the Bhopal factory. The mixing between MIC and water initiated an exothermic reaction inside of the tank. MIC gas production accelerated as the tank’s temperature continued rising, undetected, throughout the night.

The contamination incident remained undetected until shortly after midnight on Dec. 3, 1984, when Tank 610’s pressure relief valve (PRV) opened as designed to prevent an uncontrolled process release. However, this led to the discharge of 28 tons of MIC gas into the atmosphere over the next two hours. The toxic gas settled back to the ground as a poisonous fog where people living in the highly populated community outside the factory were sleeping. Panic spilled into the streets as the residents awoke, choking on the toxic air that surrounded them. Thousands of people died before daybreak. The exact number of fatalities will never be known, but it is estimated that 5,000 people died within 48 hours and up to 20,000 deaths can be related to the lingering effects of the toxic gas release. In addition, the toxic chemical release resulted in almost 500,000 injuries and massive destruction of animal life and vegetation.

The Bhopal gas tragedy raised public concern over how an industrial emergency could negatively affect community health and safety. The incident unified global industry’s commitment to making process safety management (PSM) a part of all phases of a chemical facility’s life — from design to decommissioning. Immediately after the incident, industry leaders petitioned the American Institute of Chemical Engineers (AIChE) to organize activities devoted to eliminating catastrophic process release incidents. In response to this request, the AIChE introduced the Center for Chemical Process Safety (CCPS) on Mar. 23, 1985 (2).

Over the years, CCPS has collaborated with other professional organizations to promote the global distribution of best practices to help prevent process releases and industrial accidents. These organizations are also instrumental in communicating lessons learned from industry failures of universal concern. One might expect lessons learned from the Bhopal gas tragedy to be some of the most widely communicated. However, after 40 years, the Bhopal gas tragedy remains one of the least understood incidents among a growing list of lower-consequence contemporaries.

When questions arise about how the Bhopal event could have been prevented, the discussion usually turns to managing facility siting issues and minimizing hazardous chemical inventories. In contrast, relatively little is known about how lessons from the Bhopal tragedy apply to managing problems encountered during normal process operation on a routine, perhaps even daily, basis. The information we need to form accurate conclusions about these types of lessons can be extracted from UCC’s original “Bhopal Methyl Isocyanate Incident Investigation Team Report,” which was published on Mar. 20, 1985 (3). These lessons apply directly to workers, engineers, and managers attending to the processes inside (and the safety of ordinary citizens living outside) the factories that we operate today.

This is the first of three articles specially prepared in observance of the Bhopal gas tragedy’s 40th memorial on Dec. 3, 2024. This article considers what we as engineers and operators must do to build a healthy process safety culture. Above all else, a healthy process safety culture serves as the foundation for preventing major chemical accidents or releases. Whereas many businesses respond to a process safety incident with a safety “blitz” or campaign to address underlying process safety culture defects, only those leading with a consistent process safety example succeed in developing a robust process safety culture. The 1985 report helps us to understand our part in fostering a process safety culture that can withstand the stresses of modern plant operation...