The method
Preliminary hazard analysis starts from hazardous elements — substances, energies, equipment, operations — and looks for the hazardous situations and undesired events they may cause.
For each scenario, the team records causes, consequences and existing barriers, then estimates severity and likelihood with a risk matrix. Unacceptable scenarios receive risk reduction measures or a more detailed analysis (HAZOP, FMEA, LOPA).
It is a broad, low-cost screening method, suited to designs that are not yet detailed. ISO/IEC 31010 lists it, and it is widely used in safety reports.
When to use it
- Early in a project, before detailed drawings exist.
- To map the risks of a site or activity and decide where to go deeper.
- As the first step of a safety report, before detailed analyses.
Watch out for
- Fix the rating matrix before the analysis and keep it for the whole project.
- Do not forget transient phases and maintenance, frequent causes of accidents.
- A PHA is preliminary: it does not replace detailed analysis of major scenarios.
Steps
- Define the system, its boundaries and life phases (normal operation, maintenance, start-up, shutdown).
- List hazardous elements: substances, energies, equipment, operations.
- For each, identify hazardous situations, undesired events, causes and consequences.
- Rate severity and likelihood with a risk matrix defined beforehand.
- Propose reduction measures and select scenarios for detailed analysis.
PHA software
List from the Aurorisk catalogue, links checked on 2026-09-26. Confirmed free access is listed first; unknown information is labelled.
| Tool | Source · licence · access | Scope | Description |
|---|---|---|---|
| Kenexis Open-PHA ↗ | Commercial publisherFree | United States | Integrated PHA/LOPA application, free. |
| Polyodos ↗ | Commercial publisherFree for teaching | International | PHA, FMEA, HAZOP, LOPA, bow-tie in one platform. |
| Sphera PHA-Pro ↗ | Commercial publisher | International | HAZOP, LOPA and PHA templates. |
Standards and references
- ISO/IEC 31010 — Techniques d’appréciation des risques
- ISO 31000 — Management du risque