Probability of Failure (POF) is the likelihood that a utility asset will experience a fault resulting in a spark or burning material under a given set of weather conditions. It represents the first link in the risk chain before Probability of Ignition (POI). The POF model looks at events that could potentially cause ignition (such as equipment failure, object contact, or vegetation contact) and integrates them with historical weather data to create dynamic circuit fragility curves. These curves consist of a static POF (representing the POF in windless conditions) and the dynamic exponential increase due to wind.