Root cause analysis (RCA) is the cornerstone of effective incident investigation. Rather than simply treating symptoms, RCA digs beneath the surface to find the fundamental reasons an incident occurred. When done properly, the corrective actions that emerge from RCA address systemic issues and prevent recurrence, directly reducing your TRIR and DART rates over time.
Why Surface-Level Fixes Fail
The 5-Why Method
How It Works
Starting with the incident, ask "why did this happen?" The answer becomes the basis for the next "why" question. Repeat until you reach a root cause that, if eliminated, would prevent recurrence. While the name says "5," some chains require fewer or more iterations.
Incident: Worker slipped and fractured wrist.
Why 1: Worker slipped on a wet floor. Why 2: A pipe was leaking water onto the floor. Why 3: The pipe gasket had deteriorated. Why 4: The gasket was past its replacement interval. Why 5: There was no preventive maintenance schedule for that piping system.
Root cause: Missing preventive maintenance program for piping infrastructure.
Corrective action: Establish PM schedule for all piping gaskets and seals.
When to Use 5-Why
- Simpler incidents with a relatively linear cause-and-effect chain
- Quick investigations where a structured but lightweight tool is needed
- Team brainstorming sessions to quickly explore causal pathways
- Follow-up drill-down on individual branches identified by a Fishbone diagram
Fishbone (Ishikawa) Diagram
How It Works
The Fishbone diagram (also called cause-and-effect or Ishikawa diagram) provides a visual framework for exploring all potential contributing factors. The incident is placed at the "head" of the fish, and potential causes branch off the spine into standard categories. For EHS incidents, the most common categories are:
- People - Training, experience, fatigue, communication
- Process - Procedures, work methods, sequence of operations
- Equipment - Tools, machinery, PPE, maintenance condition
- Materials - Raw materials, chemicals, supplies
- Environment - Weather, lighting, noise, housekeeping
- Management - Supervision, policies, resource allocation, culture
When to Use Fishbone
- Complex incidents where multiple factors likely contributed
- Serious injuries, fatalities, or high-potential near misses
- When you want to involve a cross-functional team in brainstorming
- Recurring incidents that have not responded to previous corrective actions
Other RCA Methods
Fault Tree Analysis (FTA)
A top-down, deductive method that uses Boolean logic (AND/OR gates) to map how combinations of failures lead to an undesired event. Best suited for complex systems where multiple failures must combine to cause an incident, such as process safety events in chemical plants.
Barrier Analysis
Examines the barriers (physical, procedural, administrative) that were supposed to prevent the hazard from reaching the worker, and identifies which barriers failed, were missing, or were bypassed. Particularly useful for incidents involving energy sources (falls, electrical, chemical exposure).
Change Analysis
Compares the conditions at the time of the incident to the normal, expected conditions and identifies what changed. Useful when an incident occurs in a process that had been running without problems, often revealing that a recent change in equipment, personnel, materials, or procedures was the trigger. Management of Change programs are designed to prevent exactly these scenarios.
Choosing the Right Method
Complex incidents (multiple contributing factors, serious outcomes): Use Fishbone to map all factors, then 5-Why to drill into each branch.
Process safety events (chemical releases, equipment failures): Consider Fault Tree Analysis or Barrier Analysis.
Incidents after a change (new equipment, new employee, procedure change): Start with Change Analysis.
Many organizations combine methods. Ecesis incident management software includes built-in 5-Why and Fishbone tools, and can be configured with custom investigation templates for your specific methodology.
Ecesis Incident Management Software
Incident Management
Built-in 5-Why and Fishbone tools with corrective action tracking.
Safety Inspections
Identify hazards proactively before they cause incidents requiring RCA.
Employee Training
Train investigation teams on RCA methodology and tools.
Task Management
Track RCA-driven corrective actions from assignment through verification.
Management of Change
Prevent incidents caused by uncontrolled changes to processes and equipment.
Mobile EHS App
Capture incident details and photos immediately from the field.
