At preliminary design stage, process designers normally lack of information on the risk level from
process plant. An inherently safer process plant could be designed if the information of risk levels could
be known earlier at the preliminary design stage. If the risk level could be determined, there is a possibility
to eliminate or reduce the risk by applying the well-known concept: inherent safety principle.
This paper presents a technique to determine the risk levels at preliminary process design stage using
a 2-region risk matrix concept. A model to calculate the severity and likelihood of a toxic release accident
was developed in Microsoft Excel spreadsheet. This model is integrated with process design simulator,
iCON to allow for data transfer during preliminary design stage. 2-region risk matrix is proposed and
used to evaluate the acceptability of the inherent risk based on the severity and likelihood rating. If the
inherent risk level is unacceptable, modification for improvement can be done using the inherent safety
principles. A case study has been carried out to illustrate the benefit of applying this newly developed
technique. It was successfully shown that an inherently safer plant could easily be designed by applying
this technique.