Publisher Summary This chapter discusses the applications of process hazard analyses on industrial facilities. The bulk of process hazard analyses will be a Hazard and Operability (HAZOP), What-If, or a Preliminary Hazard Analysis (PHA) review. PHA, HAZOP, and Security Vulnerability Analysis (SVA) reviews are generally organized and conducted in a similar fashion. The HAZOP review is more detailed and structured, while the PHA and What-If approach, which are also applied in SVAs, are typically broader, and free flowing PHA is primarily an initial hazard identification and evaluation tool in capital project proposals prior to HAZOP or other quantitative reviews later detailed design phases. The basic facilities that can be considered for a PHA and What-If review are basic fluid/gas transfer, storage, or separation systems, such as wellheads, tank batteries, pipelines (gathering and trunk), production test facilities, subsea (template) production facilities, drilling operations, wireline and workover operations, pumping stations, multistage separation systems (gas/oil/water), gas compression systems for sales, water injection systems, tank farms, liquid loading facilities (truck, rail, ship), marketing terminals, and unmanned offshore facilities. A HAZOP review method is suggested for the process when more complex facilities are under study. These facilities contain processes that typically are complex in nature, have chemical processes containing volatile hydrocarbons and toxic chemicals, or have high employee concentrations. SVAs will generally be applicable to all types of facilities; however, there will be more concern to apply its review to highly visible, valuable, and important facilities or operations. During the changes at a facility a multitude of different changes may occur, therefore the company’s management of change (MOC) procedures should define the type of analysis required by the change.