Hazard and Operability Study

Also known as: HAZOP

A Hazard and Operability Study (HAZOP) is a structured technique for identifying hazards and operability problems in a process, performed by a multidisciplinary team using guide words to prompt deviations from design intent on each section of the process.

Last updated: April 2026

Key Facts

Full name: Hazard and Operability Study
Common acronym: HAZOP
Origin: Imperial Chemical Industries (ICI), 1960s
Primary use: Hazard identification in process plants
Sectors: Chemical, petrochemical, pharmaceutical, oil and gas, food
Standard reference: IEC 61882, BS EN 61882
Typical inputs: P&IDs, design intent documents, operating procedures
Typical outputs: Hazard register, recommended actions, basis for LOPA
Typical course length: 2 to 3 days (HAZOP Leader)
Common audience: Process engineers, operations managers, safety leads
Renewal: Continuing professional development

What is HAZOP?

HAZOP is a structured workshop method led by a trained facilitator. The team works through the process node by node — typically a section of pipework, a vessel, or a unit operation — and applies guide words such as "no flow", "more pressure", or "less temperature" to each parameter. Each combination of guide word and parameter prompts the team to identify possible causes, consequences, and existing safeguards. The output is a hazard register that captures every identified deviation, the team's risk judgement, and any recommended actions. HAZOP is qualitative; quantification comes later through LOPA or other risk assessment methods.

HAZOP vs Other Hazard Identification Methods

Method	Strength	Limitation
HAZOP	Comprehensive hazard identification	Time-consuming; output quality depends on team
What-If	Faster than HAZOP	Less comprehensive
Checklist	Quick screening	Limited to known hazards
FMEA	Component-level focus	Less suited to process flow

How HAZOP Relates to Other Standards

HAZOP is codified internationally as IEC 61882. Many process facilities are required by national regulation or company policy to conduct HAZOPs at specified design phases and after major modifications. The method is referenced in IEC 61511 as a recommended hazard identification step before SIL determination. HAZOP outputs feed directly into LOPA, which uses the identified scenarios to allocate SIL to safety instrumented functions.

How Process Safety Training Providers Deliver HAZOP Training

The standard format is a 2 to 3 day HAZOP Leader course covering the method, guide words, facilitation skills, and worked examples. Some providers offer an additional HAZOP Team Member course (1 day) for engineers who attend HAZOPs but do not lead them. Most courses include a simulated HAZOP exercise on a representative plant section. External training providers deliver HAZOP as a standalone course and as part of broader process safety bundles. An LMS supporting HAZOP training needs cohort scheduling, secure delivery of confidential case studies, exercise tools that allow live team facilitation simulations, and verifiable certificates.

Common Questions

How is HAZOP different from a risk assessment?

HAZOP is a hazard identification method. Risk assessment is the broader process that includes hazard identification, evaluation, and control. HAZOP is one input to a complete risk assessment.

Do small plants need a full HAZOP?

Small or simple plants may use lighter methods such as What-If or checklist analysis. The decision is risk-based. Major hazard installations almost always require a full HAZOP regardless of size.

What goes wrong in a HAZOP?

Common failures include incomplete P&IDs, the wrong people in the room, an unskilled facilitator, rushed sessions, and weak documentation of recommendations and follow-up actions.

How often should HAZOPs be repeated?

A HAZOP is conducted at design, before commissioning, after major modifications, and on a periodic cycle, typically every 5 years for operating plants.

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