An important input to these calculations is the leakage rate and its time dependence, the time dependent behaviour of fire and its effects on equipment and structures. A safety critical system may be damaged and render inoperative once it has fulfilled it's desired function. This is taken into account in the simulations of the thermal or structural response. Calculation of the Potential Loss from Incident Scenarios Having assessed the frequency and consequence for each of the incident scenarios of the Event Tree, it is possible to calculate the statistically expected loss for each scenario. The total statistically expected loss could then be calculated by summation of the loss over all scenarios.
Several forms are available to express risks.
FAR is used to describe the work-related risk that personnel are exposed to. It does not distinguish, however, between the nature of incidents or their magnitude. A commonly used presentation form for risk to the public is the so-called risk contour. The number at a contour represents the frequency at which a person, assumed to be permanently present at the location of the contour, sustains a given level of harm. In today's economic climate designers are required to develop facilities on minimum budgets and on fast track development programmes.