A bow tie model developed for Covid-19 visualises the role of organisations in the pandemic

The bow tie method addresses major accident events and key barriers and safeguards used to manage these. Applying the same approach across other industries could prove incredibly beneficial

The oil and gas industry has been managing infectious diseases for over 40 years and has incredible knowledge that can be applied to help the ongoing Covid-19 pandemic in other sectors, writes Abdulaziz Khattak for OGN.

In the current global situation, where the Covid-19 pandemic has swept countries, a risk management methodology more commonly applied on oil and gas platforms can help make sense of the global pandemic and the efforts to stop it.

A highly effective methodology used in the energy sector to manage risks is the ‘bow tie’ model.

This analytical model has been in use for over 30 years in both the upstream and the downstream process industries, as well as other major hazard industries, and is known to have helped save lives on oil platforms, at petroleum refineries and on offshore wind farms.

A bow tie model is a risk diagram that shows how various threats can lead to a loss of control of a hazard and allow it to develop into a number of undesired consequences. The model is a summary of the controls (barriers and safeguards) that organisations rely on to protect against threats, whatever the causal mechanisms involved. The aim is enhanced communication of how major hazards are controlled.

Mark Scanlon, Head of HSE Good Practice at the Energy Institute (EI), defines bow tie as a "visual aid that identifies threats (represented as the left-hand bow of the tie) that could potentially cause a hazard (the knot) and, further, the consequences (the right-hand bow) that could result".

"In between are barriers aimed at avoiding the hazard becoming a reality, or mitigating its consequences. However, the strength of these barriers can be reinforced or undermined by degradation factors," he explains.


EI in collaboration with bow tie specialists from a number of organisations including the ABS Group, BP, HU-tech and Center for Chemical Process Safety (CCPS) has developed a specific model that visualises the role of organisations in the pandemic.

And although Covid-19 differs from conventional workplace hazards represented in bow ties, like the processing of hydrocarbons containing hydrogen sulfide or working at height, but applying the same approach is incredibly powerful, Scanlon says.

He explains: "The bow tie methodology illustrates how threats can act on hazards leading to a loss of control, which may result in catastrophic consequences. In the bow tie diagram, prevention barriers are located on the left side and mitigation barriers are located on the right side. A well-drawn bow tie clearly shows all barriers that can prevent the top event, the loss of control, from occurring or mitigate the consequences."

There are only two threats (left-hand side) leading you to catching Covid-19: airborne transfer of the virus, or direct contact with infected surfaces or people. To stop this from happening, there are prevention barriers.

In case of airborne transfer of the virus, the prevention barriers are:

• Self-isolation.

• Use of masks/protective screens (PPE).

• Washing hands before touching face.

And in the case of direct contact with infected surfaces/persons, the prevention barriers include:

• Wearing gloves (PPE) or avoid touching contaminated surfaces.

• Regular cleaning of surfaces.

• Washing hands before touching face.

The consequences (right-hand side of the bow) are only three and all are serious. These could lead to death of the infected person; death of someone he/she infects; or a protracted lockdown.

Once someone is infected, there are mitigation barriers in place to try and prevent either of the three consequences.

So, to prevent the infected person’s death, the mitigation barriers include:

• Gained, natural or vaccinated immunity.

• Low risk group (young, female, non-compromised immune system).

• Medical treatment until body fights off infection.

To prevent the second consequence, that is, infected person infecting others, the mitigation barriers could be:

• Not infectious due to gained or vaccinated immunity.

• Minimal contact (isolation at home or 2 m from others).

• Wash hands/use sanitizer.

Meanwhile, in a protracted lockdown consequence, the mitigation barrier is known antibodies testing or vaccinated immunity.


A perfect physical separation will stop all infections. But things degrade this perfection. So there is governmental guidance (or controls) to try and minimise the holes developing in the barriers. If these controls work perfectly then the barrier will continue to work.

So the self-isolation barrier, which physically separates the uninfected person from infected people, can fail due to two main degradation factors: the need to travel to buy food and to work; and unwilling to stay at home.

To control the first, you should avoid crowded public transport, work remotely, and use deliverables, neighbours for groceries; while controls for the second include peer/social pressure and intervention; and regulation, guidance and enforcement.

PPE (masks and screens) as an effective barrier can degrade due to unavailability, people not knowing how to use them, etc. People aren’t all perfect at not touching their own faces, so the controls are: remembering and following public messages and being reminded by others; wearing masks to prevent you from touching your own face; following advice to wash hands often and for 20 seconds each time.

For mitigation barriers, the medical treatment barrier is affected by many possible degradation factors that are unrelated to Covid-19 (so not relevant for this bowtie) but specifically by medical staff not being able to return to work after bring infected with Covid-19. This needs the control of the tests for antibodies:

And if we particularly focus on a key barrier of us keeping 2 m away from others to avoid infecting them, the degradation factors include:

• Infected people not following government advice: The controls here could include police intervention and fines

• The need to travel to buy food and to work: Controls include minimise trips and avoid crowded public transport; work remotely; and use deliverables, neighbors for groceries.

• A person is infected and doesn’t realise it, so he doesn’t minimise contacts: The controls include testing, testing, testing; contact tracing and quarantining of infected persons; awareness of symptoms, such as high temperature and dry cough.

• This bow tie is based primarily upon the directives and guidance from the UK Government and the Centers for Disease Control and Prevention (CDC) of the US. In all cases you should follow the directives and guidance from your own government and health institutions around the world. The knowledge and understanding of Covid-19 is increasing and the most recent directives and guidance should always be followed. Update to this bowtie can be found on https://www.energyinst.org/

• CCPS and Energy Institute have also developed a concept book, entitled ‘Bow Ties in Risk Management: A Concept Book for Process Safety’, to better define the bow tie analysis method and to show best practice ideas.