Risks with no moment
A bowtie needs a moment: the point where control is lost. Noise induced hearing loss, dust related respiratory disease, musculoskeletal strain and psychosocial wear carry no such moment; the harm accumulates. For those risks, exposure based methods are the right tool.
Decisions that need numbers
"Is this investment justified?" and "what integrity level does this safety function need?" demand numeric answers a bowtie cannot give. Those questions belong to numeric layer analysis or matrix based rating.
The inflation problem
| Symptom | Result |
|---|---|
| Dozens of threats on one diagram | Nobody reads it end to end |
| Every control written as a barrier | Real barriers disappear in the crowd |
| Two top events on one diagram | Which barrier belongs to which event becomes unclear |
False confidence
This is the most insidious limit: a full looking bowtie feels like safety. If the boxes have not passed the validity test, the diagram shows not protection but a claim of protection. That is why the test is a separate step from the drawing.
Where it is strong
For sudden loss scenarios — release, fall, collision, energy discharge — a bowtie brings teams together on one page and makes barrier ownership visible. The deciding question when choosing a method is whether the risk has a moment.