Incident outcome models

In the event of a major incident, the consequences to people will probably be less serious than predicted by the release and incident outcome models described in Chapters 2 and 3 and the effect models in Chapter 4. This is not only because of uncertainties in modeling incident outcomes or modeling limitations that may lead to conservative assumptions and results but also because of topographical and physical obstruction factors, and because of evasive actions taken by people. Evasive actions can include evacuation, escape, sheltering, and heroic medical treatment. This chapter addresses the impact of evasive actions as mitigating factors to a CPQRA study. 

For any specific incident there will be an infinite number of incident outcome cases that can be considered. There is also a wide degree of consequence models which can be apphed. It is important, therefore, to understand the objective of the study to limit the number of incident outcome cases to those which satisfy that objective. An example of variables which can be considered is as follows. 

Probit models have been found generally useful to describe the effects of incident outcome cases on people or property for more complex risk analyses. At the other end of the sc e, the estimation of a distance within which the population would be exposed to a concentration of ERPG-2 or higher may be sufficient to describe the impact of a simple risk analysis. 

It is important to understand tiiat for any specific incident tiiere will be an infinite number of incident outcome cases tliat can be considered. Therefore it is necessary to limit die number of possible incident outcome cases so that die proper consequence model can be applied. 

Specialized risk consultants and even insurance risk offices can now offer a variety of software products or services to conduct mathematical consequence modeling of most hydrocarbon adverse events. The primarily advantage of these tools is that some estimate can be provided on the possible effects of an explosion or fire incident where previously these effects were rough guesses or unavailable Although these models are effective in providing estimate they still should be used with caution and consideration of other physical features that may alter the real incident outcome. 

Effect Models Models that predict effects of incident outcomes, usually with respect to human injmy, fatality, or property damage. 

Evaluate the incident outcomes (consequences). Incident outcomes might include the total quantity of material released, a downwind vapor concentration, radiant heat fltix, or an explosion overpressure. Source models (Chapter 2) and fire and e q>losion models (Chapter 3) are the major methods used to determine these outcomes. 

Estimate the incident impacts on people, environment and property. The effect models take the incident outcomes of step 2 and determine the direct impacts— number of individuals affected, property damage, etc. Effect models are discussed in Chapter 4. 

The objective of this chapter is to review the types of models available for estimation of the consequences of accidental explosion and fire incident outcomes. 

The physical models described in Chapter 2 generate a variety of incident outcomes that arc caused by release of hazardous material or energy. Dispersion models (Section 2.3) estimate concentrations and/or doses of dispersed vapor vapor cloud explosions (VCE) (Section 3.1), physical c q)losion models (Section 3.3), fireball models (Section 3.4), and confined explosion models (Section 3.5) estimate shock wave overpressures and fragment velocities. Pool fire models (Section 3.6), jet fire models (Section 3.7), BLEVE models (Section 3.4) and flash fire models (Section 3.2) predict radiant flux. These models rely on the general principle that severity of outcome is a function of distance from the source of release. 

The next step in CPQRA is to assess the consequences of these incident outcomes. The consequence is dependent on the object of the study. For the purpose of assessing effects on human beings, consequences may be expressed as deaths or injuries. If physical property, such as structures and buildings, is the object, the consequences may be monetary losses. Environmental effects may be much more complex, and could include impacts on plant or animal life, soil contamination, damage to natural resources, and other impacts. Modeling of environmental impacts is beyond the scope of this book. 

One method of assessing the consequence of an incident outcome is the direct effect model, which predicts effects on people or structures based on prede-... 

In rodent stroke models, statin pretreatment has been shown to reduce infarct volumes and improve outcomes. Similarly, several clinical studies have shown that prior statin use reduced the severity of acute ischemic stroke and myocardial infarction. Recent studies indicate that beneftt can be achieved even when treatment is initiated after the onset of symptoms. In rodents, atorvastatin and simvastatin have been shown to reduce the growth of ischemic lesions, enhance functional outcome, and induce brain plasticity when administered after stroke onset. A retrospective analysis of the population-based Northern Manhattan Stroke Study (NOMASS) showed that patients using lipid-lowering agents at the time of ischemic stroke have a lower incidence of in-hospital stroke progression and reduced 90-day mortality rates. Retrospective analysis of data of the phase III citicoline trial showed... 

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