Process safety is paramount in the secure and viable operation of any chemical process plant. Many techniques and methodologies have been defined over the years to undertake steps that will ensure a safe operating environment at a chemical facility. However. until now, process simulation has found very little or no use in safety-related studies. This article introduces a systematic framework based on Extended Hazop (that is, Hazop supported by disturbance simulation related to process malfunctions). The F-A-tended Hazop differs from standard Hazop in documenting results., classification of frequency and consequences of process deviations, and application of a risk potential matrix (Hazop decision matrix). In this article. the Extended Hazop method is explained. Application of this method will be demonstrated in a separate article. (c) 2006 American Institute of Chemical Engineers.