Accident Investigation
Purpose and scope
Investigations establish facts, determine causal factors, and prevent recurrence; they are not disciplinary proceedings. The CSHM exam tests evidence handling, causal analysis, and corrective action quality.
Causal models
- Immediate causes: unsafe acts/conditions at the event.
- Root/basic causes: management system gaps - unclear roles, inadequate design, missing training, poor purchasing.
- Loss causation model: lack of control → basic causes → immediate causes → incident → loss.
- Tools: 5 Whys, fishbone, fault tree, timeline, barrier analysis.
Evidence and interviews
Secure the scene, photograph, sketch, collect documents (training, maintenance, JHA, permits), maintain chain of custody. Interview witnesses separately, soon, with open questions; avoid leading questions; record verbatim statements.
Worked example
A technician falls from a fixed ladder. The immediate cause is a missing handhold; the basic cause is that inspections did not cover ladders and the purchase specification did not require compliant cages. Corrective actions: repair or replace the ladder, add ladders to the inspection route, update the procurement standard, and verify with an audit. Retraining alone is inadequate because the system allowed the condition.
Traps
Stopping at employee error; blaming before facts; asking leading questions; discarding near-miss reports; writing corrective actions that are only retrain or be careful; and failing to track completion and effectiveness.