The probability of failure of an item may depend upon the time for which it is at risk (e.g., continuous running equipment) or on the conditions associated with a particular event (e.g., shock through handling, high stress transients through switching, etc.). Each must be identified separately because different reliability expressions will apply. Note that the operating failure rates for the components/parts listed in Appendix A, Data Tables, are applicable mainly to time-related, rather than event-related, applications.