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    Bowtie Analysis

    Also known as: Bow tie, Bow-tie diagram

    Definition

    A visual risk-assessment method showing the causes (left side), the top event (center), and consequences with mitigations (right side). Widely used in process safety and major-hazard industries.

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

    What the bow-tie method consists of

    A 2018 IChemE Hazards 28 paper, by authors from BP, ABS Group, CCPS and the Energy Institute, describes the book Bow Ties in Risk Management, produced by CCPS and the Energy Institute to give the chemical and process industries a consistent method and terminology. Its elements are the hazard; the top event, which is the loss of control of the hazard; the threats that could lead to it; the consequences that could follow; prevention barriers between the threats and the top event; mitigation barriers between the top event and the consequences; degradation factors that weaken a barrier; and degradation controls that help keep a barrier working. The paper notes that bow ties are also used outside the process industries, for example in aviation, mining and business risk.

    The paper's central rule is that barriers should be effective, independent and auditable, which it says typically leaves between one and five barriers on each threat pathway. It warns that long lists of supposed barriers can give a false sense of security, that an equipment item such as a shutdown valve is only part of a barrier, which also needs detection and decision elements, and that management system elements such as training, audit, management of change and contractor management influence many barriers but are not barriers in themselves. It also cautions against complicated scoring systems and says a bow tie is a means to an end, which is risk management.

    ICMM's Critical Control Management: Good Practice Guide (28 April 2026) addresses the question that a bow tie's barriers raise. Its page describes critical controls as specific measures that prevent high-consequence events or mitigate their impacts if they occur, and it says they need clear performance standards, defined ownership and regular verification. The record test is therefore the same as for the diagram: can someone see which control matters, who owns it and when it was last checked?

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    What a bow-tie record holds in software

    • A diagram per top event, with the hazard, threats, consequences and the barriers on each pathway, and a version and date.
    • A barrier record: what it is, which threat or consequence it addresses, whether it prevents or mitigates, its owner and its performance standard.
    • The reasoning for treating a measure as a barrier, including its independence from the others on the same threat.
    • Degradation factors and the controls for them, kept in view but separate from the main barriers.
    • Barrier status (verified, due, degraded or failed), with the date and evidence of the last check.
    • Links from each barrier to its supporting procedures, inspections, maintenance tasks, training and any permit or isolation.

    Bow tie, fault tree and risk matrix

    A bow tie shows pathways and barriers around a single event; it is not a calculation. A fault tree works backwards from an event to the combinations of causes that could produce it and is often used to estimate likelihood, while a risk matrix scores a hazard on severity and likelihood. A bow tie can show where the controls are and, if the organisation chooses, hold their status, but it does not itself give a frequency. A product that draws bow ties may or may not link the barriers to live inspection and maintenance data, so ask which.

    A hypothetical example: a suspended load on a building site

    This case is invented and describes no real site. A construction contractor draws a bow tie for the top event 'loss of control of a suspended load'. The hazard is the energy of a load held above people. Threats include a failed sling, a load that snags and a crane operated outside its limits. Consequences include a person struck by the load and damage to a structure below. For the sling threat the team lists a barrier, 'rigging inspected and certified before each lift', and asks the paper's tests: is it effective, independent of the other barriers and auditable? An entry that says 'training' is moved to the management elements, because it influences several barriers but is not itself one.

    On the consequence side the barrier 'exclusion zone under the load' is given an owner, the lift supervisor, and a performance standard: the zone is marked and cleared before the load leaves the ground. When a near miss shows a load carried over an unmarked aisle, the reviewer does not simply retrain the crew. The diagram shows that the exclusion-zone barrier failed, so the record marks it degraded, the actions address how zones are set in the lift plan, and a later verification returns it to verified status. The same diagram is then used to brief the next lift crew.

    Common misunderstandings about bow ties

    • A bow tie is not a risk rating. It organises controls around an event; it does not by itself say how likely the event is or how large the risk is.
    • More barriers is not better. The paper warns that long lists can give a false sense of security, and a barrier should be able to meet the effective, independent and auditable tests.
    • Procedures and training are not usually barriers on the diagram. They support barriers, and the paper suggests they appear as degradation controls or in the management system rather than as barriers themselves.
    • A finished diagram is not a managed control. If nobody checks the barrier, the diagram describes intent only, which is the gap that ICMM's call for performance standards, ownership and verification addresses.

    How bow ties relate to other glossary terms

    A bow tie sits between hazard identification and the controls that are inspected, maintained and verified, so its neighbours are terms on both sides.

    • HIRA: the wider process that identifies the hazards and top events worth drawing a bow tie for.
    • Serious injury or fatality: the outcomes whose pathways a bow tie can map, and the potential events that show a barrier failing.
    • PSM: a regulation for covered chemical processes with its own hazard analysis and mechanical integrity records, which a bow tie may reference.
    • Root cause analysis: an investigation can use the diagram to see which barrier failed and why.

    Records and evidence that usually exist for a bow tie

    • The diagram for each top event, with its version, its date and the people who built it.
    • For each barrier, the owner, the performance standard and the verification records.
    • The link between barriers and the procedures, inspections and maintenance that keep them working.
    • Records of barrier degradation or failure and how it was handled, including temporary measures.

    What a software tool needs to capture for bow ties

    • A diagram editor that keeps hazard, top event, threats, consequences, barriers and degradation factors as separate record types.
    • Fields for the barrier's owner, performance standard and independence reasoning, not just a label on a box.
    • A status for each barrier (verified, due, degraded, failed) with the date and evidence of the last check.
    • Links from barriers to inspection, maintenance, permit and training records, in both directions.

    Catalog profiles documenting bowtie and barrier management

    Same rule for every product: tagged “Barrier Management”, “Risk Assessment”, “Risk Management” or “Process Safety”, with a sourced bowtie or barrier management 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.

    Ordered by how closely our sources document this process, not by quality. Sponsored placements are labelled. How lists are ordered

    All 10 matching profiles are shown. Documentation review, not hands-on testing or a claim of compliance.

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    Frequently asked questions

    Do I need special software to draw a bow tie?

    No. A bow tie can be drawn by hand or in a general tool. Software becomes useful when barriers need owners, statuses and links to inspection and maintenance records.

    How many barriers should a bow tie show?

    A 2018 IChemE paper describes a rule that barriers be effective, independent and auditable, which it says typically leaves one to five barriers on each threat pathway. Treat that as guidance, not a limit.

    Who should take part in building one?

    People who understand the hazard and the controls in practice, such as operators, maintenance staff and supervisors, with someone who knows the method. A diagram built only by specialists risks showing intent rather than practice.

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