Incident Investigation and Emergency Preparedness
Investigation purpose and method
The purpose of an investigation is prevention, not fault-finding. A credible method includes: secure and preserve the scene and evidence; interview witnesses separately and promptly, using open questions; build a timeline; identify immediate causes, contributing factors, and root causes using a structured tool (5 Whys, cause-and-effect diagram, fault tree, change analysis); then assign corrective actions that follow the hierarchy of controls and have an owner and a due date.
Traps
The single biggest trap is accepting "employee was careless" or "retrain the worker" as a root cause. Human error is a starting point, not a conclusion - probe the design, supervision, workload, procedures, and incentives that made the error likely. Also watch for confusing immediate cause (the unguarded nip point) with root cause (the guarding standard was not applied at machine purchase). Another trap: investigations that end at the report rather than at verified corrective-action closure.
Emergency preparedness
The emergency action plan addresses reporting procedures, evacuation routes and assembly, accounting for employees, employees who remain to perform critical operations, and rescue duties. It must be written, communicated, and practiced through drills, then reviewed after drills, actual events, and organizational change.
Rule of thumb
"Human error" is where the investigation starts, not where it ends. Ask "what made this error predictable or possible?" at least three times before writing a root cause.
Worked example
A worker's hand is injured at a conveyor. Immediate cause: exposed nip point. Contributing factor: guarding was removed for maintenance and not reinstalled. Root cause: no verification step in the lockout/return-to-service procedure.