What are latent conditions and active failures?

What are latent conditions and active failures?
Ans: Inevitably, all barriers have weaknesses of some kind. Reason calls these ‘latent conditions’ as they usually only contribute to system failure when some other problem occurs. For example, a weakness of a conflict alert system is that it may lead to many false alarms. Latent conditions lead to system failure when the defenses built into the system do not trap an active failure by a system operator. The human error is a trigger for the failure but should not be considered to be the sole cause of the failure. Reason explains this using his well-known ‘Swiss cheese’ model of system failure.
In this model, the defenses built into a system are compared to slices of Swiss cheese. Some types of Swiss cheese, such as Emmental, have holes and so the analogy is that the latent conditions are comparable to the holes in cheese slices. The position of these holes is not static but changes depending on the state of the overall socio-technical system. If each slice represents a barrier, failures can occur when the holes line up at the same time as a human operational error. An active failure of system operation gets through the holes and leads to an overall system failure.