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2.1 Introduction to bowtie analysis

Risk assessment lies at the heart of any form of risk management, and one of the most powerful of these techniques is the bowtie method. Its strength is that it goes beyond the usual risk assessment “snapshot” and highlights the links between controls, assurance and verification activities, and the underlying management system; a valuable trait when assessing the constantly evolving nature of a pandemic.

Bowties originated as a method for assessing operational risk, with the earliest mention of such an approach appearing within an adaptation from the ICI plc HAZAN Course Notes 1979, presented by The University of Queensland, Australia.1 The Royal Dutch Shell Group was the first major company to integrate the bowtie method into its business practices2-4 and is credited with developing the technique which is widely used today.

The bowtie method provides a readily understood visualization of the relationships between the causes of business upsets, the escalation of such events, the controls preventing the event from occurring, and the mitigation measures in place to limit the business impact (see Figure 1).

Bowtie framework [Color figure can be viewed at wileyonlinelibrary.com]

A description of the different components of the bowtie, and the method for building such a diagram are well-documented,2, 3, 5 hence this paper focuses predominantly on its specific application within a pandemic risk management setting. Select definitions, within this context, are provided in Section 2.2, below.

2.2 Application of bowtie methodology to pandemic risk management

The application of bowtie methodology can be shifted from its more traditional use in high-hazard industries to assessing the risk to an organizations workforce during the COVID-19 pandemic in a relatively straightforward manner. Through graphical representation, bowtie analysis can map threats that may impact worker safety, identify and assess the safeguarding in place to prevent or mitigate different scenarios, and readily highlight any deficiencies or non-conformances.

A representative example of how the bowtie methodology can be applied in the assessment of “worker safety” is provided in Figure 2, with select key definitions and accompanying examples outlined in Table 1.

COVID-19 worker infection example [Color figure can be viewed at wileyonlinelibrary.com]
Bowtie definitions
Component Definition COVID-19 bowtie example
Top event: The moment when control of a hazard is lost (e.g., loss of control/containment of the hazard). Infection with the SARS-CoV-2 virus was designated as the top event.
Threats: Potential causes which could directly and independently result in the top event and are listed on the left-hand side of the bowtie diagram. Representative causes which could lead to infection with the SARS-CoV-2 virus include:

  • Close contact with infected person(s) during work hours.
  • Close contact with infected person(s) in work camp.
Consequences: Negative events which could result from the top event and lead to harm or damage. These are listed on the right-hand side of the bow tie diagram. Representative consequences resulting from infection could include:

  • Respiratory illness with severe health outcome.
  • Infection of multiple other persons (spread).
Prevention barriers: Barrier that prevents the top event from occurring and is located between the applicable threat and top event on the left-hand side of the bow tie diagram. Representative prevention barriers could include:

  • Social/physical distancing—maintaining proper distancing in certain environments will help prevent spread.
  • Face masks—face coverings can help prevent transmission of any airborne virus particles between individuals.
Mitigation barriers: Mitigation barriers are employed after the top event occurs and will reduce the magnitude of the consequence. These barriers are located on the right-hand side of the bow tie diagram. Representative mitigation barriers could include:

  • COVID-19 testing (inc. viral, antibody etc.) helps identify infection and directs subsequent activities to manage individual’s health and prevent spread.
  • Vaccinations—CDC approved vaccinations will help prevent hospitalizations and potential fatality following COVID-19 infection. Current understanding is that infections can still occur post vaccination and, as such, this has been designated as a mitigative barrier.
Degradation factors: Factors that may defeat or reduce the effectiveness of a barrier are termed degradation factors. These are applied as necessary throughout the bowtie diagram. Representative degradation factors could include:

  • Personnel unable to work from home (site-based function)
  • Increase in personnel on site (e.g., during turnaround), reduces capability for appropriate social distancing.