Understanding Reactive Chemical Incidents
In order to avoid incidents involving reactive chemical hazards, it is useful to understand the types of chemicals and types of equipment involved as well as the root causes of the incidents.
REACTIVE CHEMICAL INCIDENTS ARE A significant safety problem in the chemical process industries (CPI). The U. S. Chemical Safety and Hazard Investigation Board (CSB; www.csb.gov) conducted an investigation of incidents involving reactive chemicals and issued a report on its findings (1), including recommendations to prevent such events in the future. This article summarizes some of the Board’s key conclusions and recommendations.
What is a “reactive chemical incident”? The CSB has adopted the following definition: “A sudden event involving an uncontrolled chemical reaction with significant increases in temperature, pressure, or gas evolution that has the potential to, or has caused serious harm to people, property or the environment.”
The CSB evaluated 167 reactive chemical incidents involving 108 fatalities that occurred over a 22-yr period starting in 1980. Fifty of these incidents affected the general pubic. Yet, based on discussions with companies that track reactive incidents for their own purposes, it became clear that these 167 incidents represent just the tip of the iceberg. Most such incidents do not become known to the public and are not included in the publicly available data sources that the CSB used for its study.
Major findings and conclusions
Reactive chemical incidents are not unique to the CPI. While 70% of the incidents did occur in chemical manufacturing facilities, nearly 30% were in industries that only use or store chemicals.
Reactive incidents can occur throughout a process. It is a common misconception that reactive chemical incidents occur only in reactors. Three-quarters of the incidents occurred in other process equipment, as shown in the figure.
Table 1 summarizes the number of events involving various classes of chemicals. More than half of the incidents involved chemicals not covered by Occupational Safety and Health Administration (OSHA) process safety regulations, and over 60% involved chemicals not covered by Environmental Protection Agency (EPA) process safety regulations. These numbers highlight the significant gaps in the regulations designed to protect workers and the public from reactive hazards. In addition, OSHA and EPA standards do not explicitly require that process hazard analyses (PHAs) address specific hazards, such as reactive hazards due to thermal and mechanical shock, inadvertent mixing or runaway reaction.
Many reactive incidents are caused by inadequate recognition and evaluation of reactive hazards. This was the case in 60% of the incidents for which causal information was available. Table 2 gives a detailed breakdown of the root causes of the incidents evaluated.
The reactive chemical problem cannot be adequately defined by simply placing chemicals on a list. all chemicals can be reactive. Hazards arise from interactions in specific conditions of a chemical process that can result in an energy release or a toxic release. Thus, it’s important to address the hazards of chemicals and their combinations under specific process conditions. Although significant guidance on the technical aspects of reactive chemicals is available, the existing guidance does not effectively deal with the management of reactive chemicals.
Given the impact and diversity of reactive hazards, progress in the prevention of reactive incidents requires both enhanced regulatory and nonregulatory programs.
Recommendations
The general mission of the CSB is to prevent major chemical plant incidents by investigating events, determining the root causes, and issuing recommendations to prevent future occurrences. The recommendations that emerged from the reactive hazard investigation include:
* Expand the OSHA process safety management (PSM) standard to cover reactive chemicals more broadly.
* Improve specific elements of process safety management, such as PHAs and process safety information (PSI).
* Expand EPA’s risk management plan (RMP) activities to cover reactive chemicals.
* Improve guidance on reactive chemicals management.
* Emphasize reactive chemicals management in industry safety initiatives.
* Improve government and industry reporting of reactive chemical incidents (especially lessons learned).
* Create an industry-supported and easily accessible database of reactive chemical test data.
* Communicate the findings and conclusions of the report to stakeholders.
Some of these recommendations have been completed (although none have been officially closed out by the Board), and many others are in progress. Board members and staff have met with trade associations, companies, government, labor and public interest groups to discuss recommendations and plans to improve reactive chemical safety. As a result, many important steps have been taken.
For example, EPA will modify the RMP*Submit form and RMP*INFO software to add and define “reactive incident” to accident history reporting in RMPs. The American Chemistry Council (ACC), the Synthetic Organic Chemical Manufacturing Association (SOCMA), and the National Institute for Standards and Technology (NIST) are preparing a white paper on the development of a reactive chemical database. AIChE’s Center for Chemical Process Safety (CCPS) has written book on managing reactive chemicals (2), to which OSHA provides free online access at its chemical reactivity safety website, www.osha.gov/dep/reactivechemicals/index.html. The National Association of Chemical Distributors (NACD) has started revising the Responsible Distribution Code to address inadvertent mixing of chemicals, while ACC and SOCMA may address reactive chemical management in the rewrite of the Responsible Care management system currently underway. ACC and SOCMA are also working to make the lessons learned from reactive chemical incidents available to industry and the public.