Initiating Events, Levels of Causality, and Process Hazard Analysis

Process hazard analysis (PHA) is used to identify hazard scenarios for a process and determine if the risk from the scenarios is tolerable. Each scenario begins with an initiating event that is made up of one or more causes. These causes must be recorded in sufficient detail to allow the PHA team to determine the particulars of the scenarios and develop any needed risk reduction measures. There is a hierarchy of causality wherein there are immediate, basic, underlying, and root causes of events. A suitable level of causality must be used in PHA. This article describes the hierarchy, recommends the level that should be used in PHA, and provides guidelines for the information that should be recorded in a PHA worksheet for different types of causes. (c) 2013 American Institute of Chemical Engineers