A house event is used to represent an event that is normally expected to occur. A house event can be turned on or off. When a house event is turned on (TRUE), that event is presumed to have occurred, and the probability of that event is set to 1. When a house event is turned off (FALSE), that event is presumed not to have occurred, and the probability is set to 0. House events are useful in making parts of a fault tree functional or non-functional. House events are also referred to as trigger eventsor switching events.