Determining Root Causes—Structured Approaches

Process safety incidents are invariably the result of multiple causes, which can usually be categorized into two types: causal factors and root causes. This chapter utilizes case studies to illustrate effective root cause analysis, describes some non-proprietary tools and techniques, and presents various approaches to incident root cause analysis. The 5 Whys is a simple methodology for identifying root causes that involves repeatedly asking the question “why?”. It is a brainstorming approach to root cause identification. There are other, more structured methodologies that are useful in root cause determination. The chapter presents two structured root cause approaches: logic tree and a pre-defined tree. Structured root cause analysis uncovers the underlying reasons for human error and consequently provides guidance on suitable corrective actions. Humans make errors, so it is important to design systems that detect and correct an error before it leads to a serious consequence.