For high-risk environments such as petrochemical and chemical operations; natural gas liquids extraction plants; natural gas liquefaction plants; and refi neries, the placement of occupied buildings or facility siting is an important issue. Within such plants, facility siting is a process that assesses occupied buildings that have potential exposure to an explosion, fi re and toxic hazards. It is a continuous process that begins with an initial study and is revalidated with any changes to the facility.