Inherent safety has been recognized as a design approach useful to remove or reduce hazards at the source instead of controlling them with add-on protective barriers. It is widely accepted as a good engineering practice. However, inherent safety is based on qualitative principles that cannot easily be evaluated and analyzed, and this is one of the major difficulties for the systematic application and quantification of inherent safety in plant design. During the last few years, several measurement techniques and analysis tools have been developed to estimate the degree of inherent safety of a plant or a process unit. To address this problem, here we propose the use of fuzzy logic for the measurement of inherent safety by proposing a hierarchical fuzzy model (Gentile, 2004). This project has the objective to bring inherent safety to systematic quantification and analysis by proposing a mathematical tool to work with subjective, uncertain, and imprecise data and to incorporate information from experience and heuristic knowledge. It can be applied to process design, process synthesis, evaluation of inherent safety, process simulation, and transportation of hazardous substances. A more ambitious goal of this research is to break the traditional boundaries of safety ideology associated with the idea that safety is subjective and hence non-quantifiable. The only aspect of safety that is subjective is associated with human factors.