Hazard and Operability (HAZOP) study was originally developed for the process industries, particularly for systems involving the flow of fluids or materials. Over time, it has evolved into one of the most powerful and flexible systematic risk identification techniques, and today it forms a core element of Process Safety Management (PSM). Its structured, guideword-based approach has proven valuable far beyond chemical plants, leading to its adoption across multiple industries and disciplines.
Traditional Process Industry Applications
In its traditional form, HAZOP is used to identify hazards and operability problems in continuous process systems, such as refineries, petrochemical plants, chemical units, and fertilizer complexes. It focuses on deviations from design intent related to parameters like flow, pressure, temperature, level, and composition. HAZOP is particularly effective for systems involving the movement and transformation of materials, helping teams uncover scenarios that could lead to fires, explosions, toxic releases, or production losses.
HAZOP is equally valuable for non-operational conditions, including storage, loading/unloading, and transport systems, where risks often differ significantly from normal operating states.
Operating Modes and Lifecycle Coverage
One of the key strengths of HAZOP is its ability to examine a system across different operating states. It is not limited to normal operation; it can be applied to start-up, shutdown, standby, emergency shutdown, and abnormal operating conditions. This makes it especially useful for identifying risks that only emerge during transient or infrequent operations, which are often responsible for major incidents.
HAZOP is also well suited for batch processes and unsteady-state operations, where sequences and timing play a critical role, in contrast to purely steady-state continuous processes.
Procedures and Human-Centric Applications
Beyond hardware and equipment, HAZOP is widely applied to operating procedures, such as start-up instructions, shutdown steps, emergency response actions, and maintenance activities. By systematically challenging each step in a sequence, HAZOP helps identify weaknesses related to human error, unclear instructions, missing safeguards, or unrealistic assumptions about operator behavior.
This procedural focus has expanded into the assessment of administrative systems, where workflows, approvals, and information handovers are critical to safety and reliability.
Software, Digital, and Programmable Systems
With increasing automation, HAZOP has been successfully adapted for software applications and programmable electronic systems, including control systems, safety instrumented systems, and embedded software. Software HAZOP examines logic, data flow, inputs, outputs, and failure modes to identify potential defects, logic errors, or unsafe system responses.
This approach is now commonly applied in software and code development, particularly where failures could have safety, security, or operational consequences.
Transport, Healthcare, and Specialized Systems
HAZOP is no longer confined to industrial plants. It has been applied to transport systems involving the movement of people by road, rail, and air, where complex interactions between humans, vehicles, and control systems exist. Similarly, HAZOP has been used to assess medical devices and healthcare systems, where patient safety depends on reliable system behavior and well-defined procedures.
In these contexts, HAZOP’s strength lies in its ability to identify system-level weaknesses rather than isolated component failures.
Organizational Change and Management Systems
HAZOP has also proven valuable in assessing organizational changes, such as restructuring, outsourcing, or changes in roles and responsibilities. By applying guidewords to information flow, decision-making, and authority boundaries, organizations can identify risks introduced by change and define mechanisms to manage them effectively.
This makes HAZOP a practical tool for Management of Change (MoC), ensuring that non-technical changes do not introduce hidden risks.
Contracts, Legal Documents, and Critical Documentation
An often-overlooked application of HAZOP is the review of contracts, legal documents, and critical instructions. By systematically testing assumptions, responsibilities, interfaces, and failure scenarios, HAZOP can help improve clarity, reduce ambiguity, and prevent disputes or operational breakdowns caused by poorly defined obligations.
Similarly, HAZOP is used to test and improve instructions and procedures for critical activities, ensuring they are robust, complete, and fit for purpose.
HAZOP in Risk Management
HAZOP is an integral part of the overall risk management process and aligns with the principles of ISO 31000. It serves as a powerful risk identification tool, often forming the foundation for further analysis such as LOPA, SIL assessment, or quantitative risk analysis.
Whether applied to physical processes, digital systems, organizational structures, or information flows, HAZOP remains a versatile, structured, and proven methodology for identifying weaknesses before they lead to incidents.
Certified Functional Safety Professional (FSP, TÜV SÜD), Certified HAZOP & PHA Leader, LOPA Practitioner, and Specialist in SIL Verification & Functional Safety Lifecycle, with 18 years of professional experience in Plant Operations and Process Safety across Petroleum Refining and Fertilizer Complexes.
