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    HAZOPHazard and Operability Study

    Definition

    Hazard and Operability Study — a team method that applies guide words to process parameters to find deviations, their causes and their consequences.

    Editorial definition: The QHSE Standard, updated 3 October 2026 · https://qhsetech.com/glossary/hazop

    What OSHA, the EPA and IEC say about HAZOP

    HAZOP is short for hazard and operability study. EPA guidance on chemical accident prevention describes it as a technique first developed to uncover hazards and operability problems in chemical process plants, especially where the plant was unfamiliar with the technology, and later found useful for existing processes too. Its purpose is a systematic review of a process or operation to see whether deviations could lead to undesirable consequences. It needs an interdisciplinary team led by an experienced leader.

    In the EPA description the leader applies a fixed set of guide words, such as no, more, less and reverse, to process parameters such as flow, pressure, temperature, level and composition at each point in the process. For each deviation the team records causes, consequences, safeguards and the actions needed, or notes that more information is required. The work usually runs over a series of meetings using process drawings. IEC 61882:2016 is the international application guide, and its published summary says it covers the procedure from definition and preparation through examination sessions to documentation and follow-up.

    In the United States, 29 CFR 1910.119(e) lists HAZOP as one of the methodologies an employer may use for a process hazard analysis, next to what-if, checklist, what-if/checklist, FMEA, fault tree analysis and an appropriate equivalent. It does not require HAZOP specifically. The analysis is done by a team that combines engineering and process-operations expertise, including at least one employee with experience of the process and one member who knows the methodology. Findings must be addressed promptly and the resolution documented, the analysis must be revalidated and brought up to date within five years of the previous one, and the records are kept for the life of the process. Appendix C says different methodologies may be used for different parts of a process and gives a checklist for a boiler and a HAZOP for the overall process as an example. This is general information on the sources, not legal advice, and other regimes differ.

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    What a HAZOP record holds in software

    • The study scope: the process or procedure examined, the drawings used with their revision numbers, and how it was divided into nodes or steps, each with a statement of design intent.
    • The team: leader, recorder and members with their role and expertise, and who attended which session.
    • For each deviation: the guide word and parameter, the causes, the consequences, the existing safeguards and any action raised, or a note that more information is needed.
    • A risk rating only where the organisation's own scheme is used, with the version of that scheme.
    • Each recommendation with an owner, due date, status, documented resolution and evidence of completion.
    • Assumptions made and questions left open, such as a drawing that was out of date.
    • The study history: session dates, the next revalidation date and the changes since the last study that were reviewed.

    HAZOP, PHA and LOPA

    A process hazard analysis is the requirement or the overall activity, and HAZOP is one technique that can carry it out. LOPA is a separate later step, which an IChemE bulletin describes as building on qualitative studies such as HAZOP. A HAZOP generates and records scenarios and does not by itself calculate a risk figure.

    A hypothetical example: a new transfer line

    This example is invented and describes no real site; it shows what a study record would hold. A plant adds a transfer line between two storage tanks. The leader divides the line into nodes and states the design intent of each. For the first node the team applies the guide word more to the parameter flow. A fault in the pump speed control could send more than intended into the receiving tank, which would overfill. The existing safeguard is a high-level alarm that depends on an operator responding. The team records the cause, the consequence and the safeguard, and raises an action to review whether an independent trip is needed.

    Two entries are marked as needing more information: the relief arrangement on the receiving tank is not shown on the drawing issued to the team, and nobody present can confirm the alarm set point. The recorder logs both as questions with owners. The trip action is passed on for a layer of protection review, and the drawing is reissued under a new revision number. Until the open questions are closed the system shows the study as incomplete, and the revalidation date is counted from the study date.

    Common misunderstandings about HAZOP

    • A HAZOP report is not the same as meeting the whole process hazard analysis requirement. In the US standard the team, the elements addressed, the handling of findings, the revalidation and the retention of records matter as well as the technique.
    • The guide words are prompts, not a checklist to tick off. In the EPA description the leader applies them at each point, and a deviation that has no meaning there is set aside with a reason.
    • A HAZOP identifies scenarios. It does not produce a calculated risk figure, and a rating scheme, if used, belongs to the organisation.
    • Raising an action does not close it. OSHA requires findings to be resolved in a timely way with the resolution documented.
    • A study ages with the plant. Drawings change, so the record should show which revision was examined and what has changed since.

    How HAZOP relates to other glossary terms

    A HAZOP sits between the process safety information, the change record and the later analysis of safeguards.

    • PHA: the requirement or overall activity that a HAZOP can carry out.
    • LOPA: tests the safeguards for scenarios that a qualitative study such as a HAZOP has recorded.
    • Management of change: records changes to drawings or operation that raise the question of whether a study needs updating.
    • Process safety management: the OSHA standard in which the process hazard analysis sits.

    Records and evidence that usually exist for a HAZOP

    • The study report with scope, nodes, team and dates.
    • The drawings and process safety information used, with revision numbers.
    • Attendance records for each session.
    • Worksheets showing deviations, causes, consequences, safeguards and actions.
    • The action log with owners, resolutions and completion evidence.
    • The revalidation schedule and the records of earlier studies.

    What a software tool needs to capture for HAZOP

    • Worksheets that hold node, design intent, guide word, parameter, cause, consequence, safeguard and action as separate fields.
    • A link from each node to the drawing revision examined, so a changed drawing shows which nodes are affected.
    • Action tracking that keeps a recommendation open until a resolution is recorded with an owner and a date.
    • Support for several sessions and team members, with attendance recorded per session.
    • A revalidation date that is set and reminded, not typed into a note.
    • A software-independent export of worksheets and actions for an auditor.

    Catalog profiles documenting process safety management

    The list comes from the process safety rule. It does not show that any product supports guide-word worksheets or study facilitation, which should be tested in a demonstration.

    Same rule for every product: tagged “Process Safety”, “Barrier Management”, “Risk Management”, “Risk Assessment”, “Control of Work”, “Permit to Work” or “Asset Integrity”, with a sourced process safety (PHA, barrier or management-of-change) capability in its record, or one the vendor stated to us, labelled as vendor-stated. Documented and conditional capabilities qualify; check the linked scope before treating a module as included.

    Tekmon pays for a sponsored placement (above); its place in this list follows the same rule as every entry. How lists are ordered

    All 23 matching profiles are shown. Documentation review, not hands-on testing or a claim of compliance.

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    Frequently asked questions

    Is a HAZOP required by law?

    Not as such. US OSHA 1910.119 lists HAZOP as one of several acceptable methodologies for the process hazard analysis of covered processes, and other regimes set their own rules. Check which rules apply to the process.

    How often is a HAZOP repeated?

    1910.119 sets a maximum gap of five years between the initial analysis and each later update and revalidation. A change to the process may call for an earlier review, and other regimes use their own intervals.

    Who should take part in a HAZOP?

    EPA guidance describes an interdisciplinary team with an experienced leader. OSHA requires a team with engineering and process operations expertise, one member with experience of the process and one who knows the methodology.

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