Vital Area Penetration Significance

The use of Fault Tree Analysis has recently been recognized by security design engineers as a valuable tool in determining the protection levels which should be applied to various areas in the protected facility. This paper describes how these techniques may be extended to provide the engineer with an assessment of the significance of each of the previously defined vital areas. The technique utilizes point penetration probabilities for each of the areas to provide an index which measures the impact of penetrating the area in question upon the overall security of the facility. The effect of varying the penetration resistance of each area is then investigated. An example is provided to show how the technique is utilized by the design engineer to determine design requirements for each of the areas. While this technique has been specifically applied in this paper to the security field, it is also applicable to assessing the impact of variations in individual component reliabilities in a standard Fault Tree Analysis.