TABLE OF CONTENTS Cause and effect tree analysis (also known as fault tree analysis) begins with a known event (referred to as the top event) and describes possible combinations of events and conditions that can lead to this event. The top event in the cause and effect tree can be the loss event under investigation or a specific event that is involved in the incident.
The cause and effect tree looks backward in time to describe the potential causes of the top event. AND and OR logic is used to graphically show potential combinations of events and conditions leading to the top event.
Cause and effect trees are commonly used proactively during risk assessments to identify dominant potential contributors before an incident occurs. However, for incident investigation applications, the smallest possible tree is developed. As soon as a branch is shown not to be credible (i.e., proven false), development of that branch is stopped.
Most proactive and reactive analysis techniques only identify single-event failures. One significant advantage of the cause and effect tree technique is that it can help identify multiple-event failures. Multipleevent failures are those that require more than one event for a failure to occur. For example, for a fire, three conditions must exist simultaneously: fuel, oxygen, and an ignition source. Most incidents involve multiple-event failures. Therefore, the ability to model multiple-event failures is an essential element for any incident modeling methodology.
A cause and effect tree can also show design and operational...
