Risk tree INDEX

Methods for performing hazard analysis and risk assessment include safety review, checkhsts, Dow Fire and Explosion Index, what-if analysis, hazard and operabihty analysis (HAZOP), failure modes and effects analysis (FMEA), fault tree analysis, and event tree analysis. Other methods are also available, but those given are used most often. 

The ICI-MOND Fire Explosion and Toxicity Index (ICI 1985) was derived from DOW one and it is yet appreciated in process industry in many countries, including Italy. In ICI-MOND index method there are some ninety elementary questions, nested in a three levels tree. For many issues there is also a forth level of nested questions. About two thirds of the questions are for penalties and one third for credits accounting. For the most of the questions a quantitative answer is required. The questions are organized in chapters for penalties section the subjects are related to materials and quantities, processes and equipment, layout, health for credits section instead the method deals with containment, control, safety culture, fire engineering and emergency preparedness. Every issue weighs differently in overall risk levels accounting. Results are presented in a structured way, discriminat-iug fire, toxic, confined and unconfined explosion. 

Software System Hazard Analysis This type of analysis is conducted similar to a hardware system hazard analysis (SHA), analyzing software functional processing steps to determine whether they may have any particular hazardous effect on the system. The analysis utilizes a hazard-risk index to illustrate the severity of each potential failure. The main advantage to this method is in its ability to positively identify safety-critical hardware and software functions as well as consider the effect of the human element in system software operations. The results of the software SHA, which identifies single-point failures or errors within a system, can often be used to assist in the development of a software fault tree analysis or, to some degree, a system FMEA. However, as with the other various SWHA techniques briefly described above, this method is also time-consuming and costly to perform. 

The safety index is based on the classical indexing method—weighting the safety and hazard measure (which is dependent on the Best Case path of Event Tree). As we consider the spent time of the personal in the endangered area, the calculated risk can be acceptable if the probability of the presence of personnel is very small. In the other hand, the frequency of a fire at the enterprise is also small but safety measures can be unacceptable. This gives a signal to the auditor that safety measures have to be raised. 

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