Finding All the Hazards How Do We Know We Are Done?
- Susan Cantrell | Pat Clemens
- Document ID
- American Society of Safety Engineers
- Professional Safety
- Publication Date
- November 2009
- Document Type
- Journal Paper
- 2009. American Society of Safety Engineers
- 0 in the last 30 days
- 134 since 2007
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IN THE PRACTICE OF SYSTEM SAFETY, hazards are threats of harm to assets that one wants to protect. These assets may include life, limb, health, equipment, the environment or productivity. System safety practitioners seek to identify the hazards posed both by and to a system. Risk that each hazard poses to each asset is then assessed in terms of the severity and the probability of the potential harm. Risk at intolerable levels must then be abated or accepted (Ericson, 2005; Manuele, 2008). The most fundamental step in practicing system safety is identifying the hazards. If not practicedwell, then all that follows is crippled. Hazards remain unidentified and unmitigated, erroneous assumptions about safety of the system are made and used for future planning, and people and hardware are put at risk unawares. The adage is true, “If you can't find the hazards, you can't practice system safety.” In the system safety literature, much is made of the importance of identifying hazards.Authors in the field describemany independentmethods for hazard discovery. Manuele (2008) presents a list of 10 basic methods. The fact that there are somany variedways to identify hazards indicates that finding all of them is more than casually challenging. Little has been reported in the literature concerning the thoroughness with which the analyst may expect to identify system hazards. Of 11U.S.-published textbooks recently consulted for information on the topic, only one (Leveson, 1995) provided definitive information on the subject. Even the encyclopedic and well-indexed three-volume Lees' Loss Prevention in the Process Industries (Mannan, 2005) makes no mention of the matter of thoroughness in hazard discovery. Can that first step in this system safety process, finding the hazards, be done exhaustively? Or can it be performed only with questionable thoroughness? Dare a system safety engineer ever claimto have found all hazards in a system? If one admits to finding fewer than all of them, what portionmight have beenmissed? Iswaiting for a loss event the only sure way to identify an additional hazard? SH&E professionals must be able to address fundamental but troubling questions such as these. The Measurement Challenge: Do We Find All the Hazards? The purpose is not to revisit themanyways of finding hazards, nor to stress the importance of doing so, as the literature already contains much on those subjects. Rather, the purpose is to address the questions, Do we ever really find all of the hazards? What must we do to at least optimize our process? Admitting to finding fewer than all of themrequires both an understanding of that failure and a method for expressing this less-than-perfect degree of thoroughness. To determine what proportion of all hazards within a system have been identified by any particular technique, one must first establish how many hazards actually exist within the system. Figure 1 helps illustrate this paradox. As shown, each of many analytical methods will identify some system hazards. Each may also find some that are found by others. But no single method will find them all.
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