Factor of safety versus redundancy - the cliff-hanger question

Imagine you were hanging off a cliff. Is it safer to be attached to two ropes or a single rope that is twice as strong? This question was raised in response to a proposition advocated during a previous Fire Safety Engineering Conference that redundancy can be quantified using factor of safety. Considerable debate ensued but the question remained unanswered. In order to answer the above question, this paper presents a detailed examination of the two key design aspects - factor of safety and redundancy. This paper demonstrates that a high factor of safety does not guarantee a low probability of failure, or a high level of safety. In order to raise the bar for fire safety engineering designs and to ensure that a high level of safety is achieved, one must look beyond using factor of safety as the sole design criteria. Failures of components and system must be carefully examined to ensure sufficient redundancy and robustness of the designs.