House event in FTA

[Ram Sudhir]

Hi all,
I want a little more explanation on House event in FTA. Following is the way it is explained in NASA handbook on FTA.
"The house is used to signify an event that is normally expected to occur: e.g., a phase change in a dynamic system. Thus, the house symbol displays events that are not, of themselves, faults."

Can anyone explain the above with a small example house event??


Thank You.


Regards,
RamSudhir

[adam]

A house event is used typically in "what if" situations. For example, you want to know the probability of a top event given that a certain has occurred (e.g., the effect of a valve being stuck closed or open in a system). With house events you force the probability to be either 1 or 0.