Beware of the Black Swan

In 16^th century London, a statement that describes impossibility was referred to as a “black swan” because all historical records of swans up to that time had reported that swans only had white feathers. The Greek philosopher Aristotle first used the term “white swan” as an example of necessary relations and the term “black swan” as the expression of the improbable. Nassim Nicholas Taleb in his recent book entitled The Black Swan, The Impact of the Highly Improbable discusses the extreme impact of rare and unpredictable events (black swans) and the human tendency to find simplistic explanations for these events after they occur. Those of us that attempt to evaluate risk must understand that black swan events cannot be predicted using current risk analysis tools. We must also remember the lessons learned from previous black swan events when designing and operating new chemical processing facilities.

This paper will discuss the concept of the black swan as applied to chemical process risk assessment. Lessons learned from black swan events of the past and the applicability of these lessons to the design and operations of existing and new chemical processing facilities will be discussed. The limitations of LOPA and other risk analysis tools in predicting blacks swan events will be examined. The discussion on the limitations of risk analysis will include examples of hazards scenarios where risk analysis tools such as LOPA may not be appropriate.