What is the Bow-Tie model in process safety?

• A. A visualization of hazard scenarios showing the hazard on the left, potential threats leading to the top event, barriers in between, and consequences on the right; demonstrates risk management.
• B. A purely financial diagram used for budgeting safety investments.
• C. A map of plant layout showing safety equipment.
• D. A procedure for incident reporting.

Answer: (A)

The Bow-Tie model is a risk visualization that centers on a top event and shows how hazards and threats on the left can lead to that event, with barriers in the middle to prevent or mitigate it, and consequences on the right, along with actions to manage those outcomes. This layout highlights how preventive barriers stop the transition from hazard to top event, while mitigative barriers limit the impact if the top event occurs. It also clarifies who is responsible for each barrier and where gaps may exist.

For example, in a chemical plant, a hazard like flammable material combines with threats such as equipment failure to create a potential release (the top event). Preventive barriers on the left might include proper process design, leak detection, and routine maintenance. If the top event occurs, mitigative barriers on the right—like fire suppression, emergency shutdown, and ventilation—help limit consequences such as a fire or toxic exposure. This structure makes it easy to see where safeguards exist, which barriers could fail, and what needs to be added or monitored.

Other options described financial budgeting, a plant-layout map of safety equipment, or a procedure for incident reporting, none of which capture the left-to-right hazard-to-consequence logic and the barrier emphasis that define the Bow-Tie model.