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Set of circumstances that leads to failure.

The failure cause may originate during specification, design, manufacture, installation, operation, or maintenance of an item (IEV 192‐03‐11). The failure cause may be an action, an event, a condition, a factor, a state, or a process that is – at least partly – responsible for the occurrence of a failure. To be responsible for a failure, the cause must be present before the failure occurs, and the presence of the cause should increase the likelihood of the failure.

When studying several similar failures, we should see a positive correlation between the presence of the cause and the occurrence of the failure(s), but positive correlation is not a sufficient condition for claiming that something is a cause of a failure. It is very easy to find correlated factors that are totally unrelated. The correlation may, for example, be that the two factors are both caused by the same third factor. Causality is a complicated philosophical subject. A lot more information may be found by searching the Internet. The authors especially recommend consulting (Pearl 2009).

Several failure analysis techniques have been developed to identify the causes of a failure that has occurred. Among these are cause and effect analysis and root cause analysis that are described in Section 3.7.