Acceptable risk design issues

Guidelines issued by the semiconductor industry provide another indication of a trade association having recognized the value of hazard analysis and risk assessments in the design process to eliminate or control hazards and to attain acceptable risk levels. To do what the issued guidelines propose requires that manufacturers have persoimel on their staffs who are skilled in hazard analysis and risk assessment. 

A convincing statement is made, as in the following excerpt, about the need, sometimes, to go beyond issued safety standards in the design process and to have decisions on acceptable risk levels be based on risk assessments. This excerpt is taken from Related Information 1— Equipment/Product Safety Program, which is an adjunct to SEMI S2-0706, Environmental, Health, and Safety Guideline for Semiconductor Manufacturing Equipment. 

Once tlie system components and their failure modes have been identified, tlie acceptability of risks taken as a result of such failures must be determined. Tlie risk assessment process yields more comprehensive and better results when reliable statistical and probability data are available. In tlie absence of such data, tlie results are a strong function of tlie engineering judgment of tlie design team. The important issue is tliat both tlie severity and probability (frequency) of the accident must be taken into account. 

The validation goal italicized above mentions that model output should simulate reality with some speeified degree of precision. Increasing frustration comes fi om this implicit and extraordinary assumption that data measured in the field reflects reality more elosely than model output. This issue became apparent during the FEMVTF process [10] and has also been mentioned by other authors. It should be sufficient to validate a tier 1 model designed to be protective in risk assessments by demonstrating that it is consistently more protective than the accepted tier 2 model that follows it in the stepwise process. However, in all other validation approaches, some measured field data is needed. Questions that must be asked about the generation of the field data used for validation include ... 

Broader issues also should be considered. One is the severity and impact of the effect and how easy it would be to monitor and reverse the toxicity in clinical trials. The therapeutic indication is important, particularly when assessing if the toxicity is tolerable for the disease indication. For example, a low-grade toxicity may be acceptable as a side effect of a cancer drug, yet it may be completely intolerable with a drug designed to control obesity. More broadly, the company s overall portfolio balance and how much risk the company is prepared to accept for the particular project come to bear on decision making. 

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