While consequence analysis determines the impact that a given hazard may pose to people, equipment, or structures, risk assessment seeks to determine the likelihood that a given accident scenario will occur. This will involve examining the failure rates of equipment, movement of people in the area affected by the hazard, statistical variations in weather conditions in the area and any other factors which affect the likelihood that people or equipment will be exposed to the hazard. When all of the potential hazards are combined with the expected frequency of their occurrence, a measure of risk is determined that can be compared to an appropriate risk acceptability standard. Depending on the system being modeled, both individual and societal risk criteria might apply. These criteria might take several forms:
Individual probability of death per annum
Once the elements that drive a quantitative risk assessment study have been identified, it is possible to re-examine the system to determine the most effective means to lower or minimize risk posed by a hazardous situation.