These are six systematic and integrated studies conducted to identify safety, health and environmental aspects and operability problems of processes through all stages of the project life cycle.

Hazop 1 (Preliminary Hazard Review)
Done at the very early stage of any project or modification to identify safety heath & environmental aspects of the materials in the process, which needs further attention. Also provide information for compiling the Environmental Impact Assessment.

Hazop 2 (Plant and Equipment Major Hazard Review)
Carried out at the conceptual design stage when plant and equipment have been selected to identify and assess hazards in terms of fire, explosion, and toxic release. This provides information for Major Hazard Installation Risk Assessments.

Hazop 3 (Detailed Examination of the Design)
Done at the completion of the basic design to identify hazard and operability problems, which could originate from deviations in the design.

Hazop 4 (Plant Review)
Once construction has been completed and before commissioning a review is carried out to ensure that all the provisions from the preceding studies have been incorporated in the built plant.

Hazop 5 (Safety Health and Environmental Audit)
Done before startup in order to ensure compliance with legal and organizational risk management programs e.g. NOSA

Hazop 6 (Operational Review)
A final review to confirm that the actual operation meets all the Safety Health and Environmental requirements and is operable.