Rethinking Safety: Why the Hierarchy of Control is Outdated, Misleading, and Too Rigid for Risk Assessments

The Hierarchy of Control (HoC) in Occupational Health and Safety (OHS) has been criticized for being outdated, misleading, and overly rigid. For several reasons, many thought leaders and safety professionals have challenged traditional safety models, including the HoC. Since its introduction in the 1950s, the hierarchy of controls has remained central to workplace safety laws and regulations. For most, safety is about controlling hazards, and the tool of choice is the Hierarchy of Control. It is enshrined in safety legislation, textbooks, inductions, and training courses, and government authorities recommend it as the preferred method for eliminating or mitigating hazards.

Understanding Hierarchy

A hierarchy is a structured system in which elements, people, or things are ranked or arranged in levels of importance, authority, or status. Examples include:

• Organizations: A company may have a hierarchy with the CEO at the top, followed by senior managers, middle managers, and employees.
• Society: Social hierarchies exist based on wealth, status, or class.
• Systems: Classification systems, such as the biological taxonomy of species, follow a hierarchical structure.

The Difference Between Hazards and Risks

The Hierarchy of Controls was primarily designed to control hazards, not risks directly.

• Hazards are sources or situations with the potential to cause harm.
• Risk involves uncertainty about the consequences of an activity and the potential impact on human health, safety, well-being, wealth, property, or the environment.

Safety is concerned with hazards that may result in incidents causing harm to people, property, and the environment. Risk, in the safety field, is typically defined as the "likelihood and severity of hazardous events." Safety risks are controlled using risk assessment techniques.

The Five Levels of the Hierarchy of Controls (ISO 45001)

The hierarchy of controls in Occupational Health and Safety Management Systems (OHSMS) is a method for identifying and ranking ways to protect workers from hazards. It is an inverted pyramid with five levels, ranked from most to least effective:

1. Elimination – Remove the hazard entirely.
2. Substitution – Replace hazardous processes, materials, equipment, or operations with less hazardous ones.
3. Engineering Controls – Use engineering solutions to reduce or eliminate hazards.
4. Administrative Controls – Implement training, procedures, and work practices to reduce exposure.
5. Personal Protective Equipment (PPE) – Use adequate PPE as a last line of defense.

Breaking It Down: Hazard vs. Risk Control Measures

• Elimination and Substitution focus on hazard control by removing or replacing the source of potential harm.
• Engineering Controls, Administrative Controls, and PPE focus on risk control by managing exposure to hazards and mitigating potential consequences.

Quote: "The requirement for the hierarchy of controls is intended to provide a systematic approach to enhance occupational health and safety, eliminate hazards, and reduce or control OH&S risks. It is a widely accepted system used by safety organizations."

Risk Control vs. Hazard Control

• Hazard control eliminates or reduces the presence of hazards (e.g., removing a dangerous machine).
• Risk control manages exposure and consequences when the hazard cannot be eliminated (e.g., using ventilation or PPE).

Risk treatment involves selecting and implementing measures to modify risk. It is a key step in the risk management process.

Misalignment Between the Hierarchy of Control and Risk Assessment

1. Purpose of the Hierarchy of Control vs. Risk Assessment

• Hazard HoC prioritizes control measures from most to least effective.
• Risk assessment evaluates risk levels and determines appropriate risk controls.
• Confusion arises when Hazard HoC is misapplied as a risk control framework rather than a hazard management strategy.

2. Why Certain HoC Controls Don’t Fit Well in Risk Assessments

Control Level

Issue in Risk Assessment

Elimination

Removes the hazard, so there is no risk left to control. Not a safeguard or a barrier.

Substitution

Reduces hazard severity but does not provide a concrete barrier or defense.

Engineering Controls

Effective, measurable, and enforceable control. Provides a physical barrier.

Administrative Controls

Helps shape behavior and compliance but is dependent on human actions.

PPE

Acts as a barrier but does not prevent hazards, only mitigates consequences, designed to prevent exposure or reduces the severity.

3. Why Engineering and Administrative Controls Are Best for Risk Assessments

• Engineering Controls provide structured and measurable risk reduction.
• Administrative Controls ensure compliance and modify behaviors.
• Elimination and Substitution remove hazards but do not function as defensive risk controls.
• PPE mitigates exposure but does not address the root cause.

Limitations of the Hierarchy of Controls

1. Lack of Consideration for Human Behavior and Risk Psychology Safety is influenced by human decision-making, risk perception, and organizational culture.
2. Misinterpretation as a Strict, Step-by-Step Process Controls often overlap, and multiple strategies may be required.
3. Not Fully Aligned with Advanced Risk Assessment Techniques Modern risk management frameworks (ISO 31010, Human and Organizational Performance, Safety Differently) emphasize adaptability and real-world complexities.
4. PPE as a Reactive Control Yet Still Essential PPE is often the first line of defense, especially in high-risk industries. and not as the last resource and least effective as argued
5. Over-Reliance on Elimination Instead of Systemic Risk Management Industries such as oil & gas, mining, and chemical processing cannot always eliminate risks.
6. Oversimplification of Risk Complexity Real-world hazards are interconnected and require a holistic approach.
7. Potential to Stifle Innovation Strict adherence to HoC may prevent the adoption of new risk management solutions, such as AI-driven monitoring, and drones for inspections.
8. Risk of Misapplication Many risk assessment templates incorrectly apply HoC as a risk control framework.
9. Economic and Practical Limitations Cost and feasibility of elimination and engineering controls often pose challenges.
10. Lack of Integration with Risk Assessment Software

• HoC is not easily integrated into digital risk management tools, requiring significant customization.

Rethinking Safety: Moving Beyond the HoC

Rather than strictly following the HoC, organizations should adopt a more dynamic approach:

• Consider the full risk management process rather than relying solely on hazard control.
• Incorporate human factors, organizational culture, and technology into risk management.
• Leverage advanced techniques like ISO 31010 and HOP for continuous learning and adaptability.
• Prioritize a mix of control measures that balance effectiveness, feasibility, and sustainability.

By rethinking the traditional approach to safety and acknowledging the limitations of the HoC, organizations can foster a more effective and comprehensive safety risk assessment that aligns with modern risk management principles.