The Five Levels of Hierarchy
The hierarchy ranks hazard control methods in order of decreasing effectiveness:
Elimination – Remove the hazard entirely.
Substitution – Replace the hazard with something less hazardous.
Engineering Controls – Design physical changes to isolate people from the hazard.
Administrative Controls – Implement procedures, training, and policies to reduce risk.
Personal Protective Equipment (PPE) – Use equipment to protect the individual from residual hazards.
This order encourages organizations to consider inherently safer systems first and rely less on measures that depend heavily on human behavior or ongoing compliance.
Inherently Safer Design (ISD)
ISD enhances process safety management by reducing hazards through strategic design and operational practices. ISD presents a holistic approach to safer chemical processes. Practical applications include substituting chemicals, minimizing risks, and ensuring safety during commissioning.
Order of Risk Reduction under ISD
First Order: Elimination of hazards
Second Order: Risk reduction through substitution or minimization
HCA Applications
In Process Hazard Analysis (PHA), every identified risk or hazardous scenario should be systematically examined through the lens of the hierarchy. According to CCPS guidelines and widely adopted industry practice, each safeguard identified during a PHA session should be categorized by control order.
Best Practices for Applying HCA
- Label controls during PHA as first, second, or third order.
- Develop a formal HCA worksheet with justification fields.
- Prioritize inherently safer designs during early product phases.
- Incorporate HCA reviews in MOC and PSSR workflows.
- Use bowtie analysis or LOPA to assess the actual risk reduction from proposed controls.
Learn how Hierarchy of Controls Analysis can strengthen your risk management program.
