In recent years virtual reality techniques have been widely used to design industrial systems. Naturally risk assessment and risk visualisation can be one of the most useful applications of these techniques. However traditional risk analysis approaches are not appropriate for the presentation of dangers in virtual environments. Also there are operational difficulties related to using the sophisticated mathematical models to evaluate the effect of various parameters in risk assessment in real time. A new approach by the extraction of the fuzzy set concept is proposed to satisfy these requirements. The severity of the hazards in this method is presented as a characteristic of the zone around the hazardous object and is calculated as the degree of membership in the dangerous zone. This method is useful for scenario-based risk analysis, through the design processes.