HAZOP is based on a theory that assumes risk events are caused by deviations from design or operating intentions. Identification of such deviations is facilitated by using sets of “guide words” as a systematic list of deviation perspectives.

HAZOP methodology helps to stimulate the imagination of team members when exploring potential deviations & probable causes for the deviation. It is then followed by identifying the existing set of controls & to study whether those are sufficient to stop the deviation & additional controls if required.