VULNERABILITY MODELS

"The moving finger writes; and, having writ, moves on: not all your piety nor wit shall lure it back to cancel half a line, nor all your tears wash out a word of it. " (Omar Khayyam)

There is a sense of irreversibility in the impact of release of hazardous materials on vulnerable receptors. This has also influenced the risk perception among members of the public.
Having determined the physical effects from release events, it is important to relate the effects to final impacts on vulnerable receptors. This is the area of vulnerability analysis in hazard assessment. Although a well accepted analysis tool, the predictions can be accompanied by significant uncertainty that needs to be taken into the decision-making process. It is vital that the estimates are done with substantial knowledge of the source and circumstances under which vulnerability models have been developed.

THE ROLE OF VULNERABILITY MODELS
In Section 5.2, we have said that there are two steps in determining consequences from hazardous incidents. These are:
• the physical effects of the event (gas concentrations, thermal radiation levels, explosion overpressures)
• the damage caused to the vulnerable receptor (injury, death, level of bums, structural damage, environmental impairment)

The damage aspects are addressed by vulnerability models, using doseresponse relations. Dose-response data and the equivalent graphical representations show the outcomes or response of a dose on people, animals, structures or any nominated receptor. The dose can represent a quantity of a chemical exposure, an impulse from an explosion or a thermal dose. The response represents the level of injury sustained, deaths, physical damage to equipment or level of impairment. Hence the dose-response relation is a generic and common means of representing this relationship.