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Different
groups often perceive risks in very different ways. For
instance, there is a sharp contrast between the way technical
experts view risk and the way risk is seen by the general
public. Whereas the public tends to assess risk subjectively,
relying on intuition and measuring risk qualitatively,
engineers use quantitative measures and rely on a process
or logical relationship. There is no universally recognized
standard for what constitutes "acceptable" risk.
While such extreme situations as the Bhopal incident are
clearly unacceptable, events such as the release of pungent
odors or loud noises may also be unacceptable, depending
on the surroundings.
As shown in Figure 1, three elements determine "risk:"
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The
causes which may initiate and contribute to a failure; |
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The
particular potentially hazardous condition or failure
which may result from the cause |
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The
consequences which may derive from the particular
potentially hazardous condition or failure. |
The sequence of events, or scenario, leading to a consequence
of concern can be characterized by two parameters: its
likelihood, measured as a probability or a frequency,
and the impact of the consequences, measured as personnel,
property, environmental and/or economic loss.
Figure 1 shows how the risk associated with a scenario
is a function of the likelihood and the impact magnitude,
and is usually taken as the product of both variables,
thus measuring the expected value of the loss.
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