THE OBJECTIVE OF SAFETY ACTIVITIES IS TO KEEP HIGH PROBABILITY

CONDITIONS OR ACTIONS OF ANY KIND FROM CAUSING LOW PROBABILITY ADVERSE EVENTS.

Another example is the Concorde crash. In the case of the Concorde crash, a high probability condition, namely a foreign object on a runway, caused a low probability adverse event, the destruction of a Concorde supersonic transport, the loss of all on board, and the grounding of the Concorde fleet for an extended period.

The classic example in the nuclear industry is the incident at Three Mile Island, where water intrusion into the air system resulted in permanent closure of the facility.

Another classic from the chemical industry is the toxic release at Bhopal, where a routine cleaning task resulted in killing thousands of people outside the fence.

Another classic is the fire that permanently shutdown the Unit 1 reactor at Browns Ferry, where a routine leak test on one of the other units initiated a fire that nearly caused a meltdown of Unit 1.

A final example is the sinking of the ship The Herald of Free Enterprise, where a routine

departure resulted in loss of the ship, some of the crew, all of the cargo, and many of the passengers. Thus, all safety activities are appropriately directed toward keeping high probability events from causing low probability adverse events. A high probability event is anything that wouldn't surprise us, e.g., starting up our facility after an outage, repairing a lighting circuit, making a facility modification, replenishing lubrication reservoirs in the switchyard, moving a mobile crane, troubleshooting an equipment problem, and the like.

Note that the high probability events in the above examples were by no stretch of the imagination, "root causes".