Critical State

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in a states-transitions model, state belonging to a given class of states and which is distant from the

failure class of states by only one transition

Note 1 to entry: This is a mathematical concept in relationship with e.g. Markovian process or Petri nets models.

EXAMPLE The states of a safety system can be sorted out into two classes: class OK when the safety action is

available and KO when the safety action is inhibited. In this case a critical state with regards to the safety system

failure belongs to the class OK and only one failure (i.e. on event) is needed to have a transition to the class KO.

Source: ISO/TR 12489:2013(E) Reliability modelling and calculation of safety systems. Global Standards

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