Let us analyse this proposition from the point of view of barriers in Chapter 7. Occupational accident statistics are dominated events where a single barrier failure is sufficient for a hazard to cause harm. for exanlple, the case where operator handles a tool such as a chain saw. The chain represents a hazard and may cause harm if the operator docs not handle the saw about is also hazardous due to the risk of the same level or to a lower or The operator has to track of the hazards in the environment all the time. To avoid the operator has to control the hazards uncontrolled d. 7.1) or stay the the source of energy and the victim in time or Most of the time the operator will be to handle the hazards. In rare due to moment of of concentration or for some other reason, the operator fails to track of and control or avoid the and an accident follows. Since man is not 100 per cent reliable, we must expect accidents to happen in a working environment where there are hazards present.