Hierarchy of Controls: A Practical Guide to Workplace Risk Control
The hierarchy of controls provides a structured approach for selecting workplace risk controls, giving priority to measures that address hazards at their source before relying on worker behavior or personal protective equipment.
What Is the Hierarchy of Controls?
The hierarchy of controls is a framework used to consider different methods of controlling occupational hazards. It organizes control measures according to how they interact with a hazard and the people who may be exposed.
The basic principle is straightforward: where practicable, controlling a hazard at its source is generally preferable to relying solely on people to avoid exposure.
The hierarchy is commonly presented as elimination, substitution, engineering controls, administrative controls and personal protective equipment. In practice, effective risk management may require a combination of these measures.
The Five Levels of the Hierarchy of Controls
Each level represents a different approach to reducing exposure or controlling a hazard.
1. Elimination
Remove the hazard so that the associated exposure no longer exists.
2. Substitution
Replace the hazard, material, process or equipment with an alternative presenting less risk.
3. Engineering Controls
Use physical or technical measures to isolate people from the hazard or reduce exposure at its source.
4. Administrative Controls
Use procedures, training, scheduling, supervision and other work practices to influence how exposure is managed.
5. Personal Protective Equipment
Use suitable protective equipment to reduce a person’s exposure when hazards cannot otherwise be adequately controlled.
1. Elimination: Remove the Hazard
Elimination addresses the hazard by removing it from the work or process. When elimination is feasible and properly implemented, exposure to that particular hazard can be prevented rather than managed after it occurs.
For example, redesigning a task so that a hazardous activity is no longer required may eliminate the associated exposure. Eliminating unnecessary work at height is another example where changing the work itself may remove a hazard.
Elimination is often easier to consider during planning and design than after equipment, processes and facilities are already established.
2. Substitution: Replace the Hazard
When elimination is not practicable, substitution considers whether a hazardous material, process, tool or piece of equipment can be replaced with an alternative presenting less risk.
A substitution should be evaluated carefully. Replacing one hazard can unintentionally introduce another, so the alternative should be assessed before implementation.
The objective is not simply to make a change. It is to achieve a meaningful reduction in risk without creating unacceptable new hazards.
3. Engineering Controls: Isolate People from Hazards
Engineering controls change equipment, processes or the physical work environment to reduce exposure. They can be particularly valuable because they may operate with less dependence on repeated individual decisions.
Machine Guarding
Physical guards and barriers can help prevent access to dangerous moving parts or hazardous areas.
Ventilation
Appropriate ventilation systems can capture or reduce airborne contaminants and help limit occupational exposure.
Isolation
Physical separation, enclosures or remote operation may help keep people away from hazardous processes or energy sources.
4. Administrative Controls
Administrative controls influence how work is organized and performed. They do not normally remove the underlying hazard, but they can help reduce exposure when properly designed and implemented.
Examples may include safe work procedures, training, warning systems, access restrictions, permit systems, job rotation where appropriate, scheduling, inspections and supervision.
Because many administrative controls depend on people consistently following defined practices, implementation, communication and supervision are important to their effectiveness.
5. Personal Protective Equipment
Personal protective equipment, commonly known as PPE, creates a protective barrier between a person and a hazard. Depending on the work, examples can include protective clothing, gloves, eye protection, hearing protection, safety footwear, helmets and respiratory protection.
PPE can be essential, but it generally does not remove the hazard itself. Its effectiveness can depend on correct selection, fit, use, maintenance, storage, inspection and replacement.
For this reason, PPE should be considered within the wider risk-control strategy rather than automatically treated as the first or only solution.
Using Multiple Levels of Control
The hierarchy of controls does not mean that every workplace hazard can be addressed using a single measure. Complex risks often require several controls working together.
For example, an organization might use an engineering control to reduce exposure, establish procedures for the remaining risk and provide appropriate PPE for residual exposure.
Combining controls can provide additional protection, particularly where no single measure can adequately manage the risk.
Choosing Appropriate Workplace Risk Controls
Control selection should begin with a clear understanding of the hazard and the associated risk. The hierarchy can then be used to consider whether measures higher in the hierarchy are reasonably practicable and appropriate to the situation.
Understand the Hazard
Identify the source of harm, exposure pathways and people who may be affected.
Evaluate the Risk
Consider the nature and significance of the risk and the effectiveness of existing controls.
Select Controls
Consider higher-order measures first and combine controls where necessary.
Verify Effectiveness
Check whether implemented controls work as intended and continue to manage the risk.
Review the Effectiveness of Risk Controls
Implementing a control is not the end of the process. Controls should be checked to determine whether they are functioning as intended and whether they have introduced new hazards.
Review may involve workplace observations, inspections, worker feedback, maintenance information, exposure information, incident data or other evidence appropriate to the control being evaluated.
Controls should also be reconsidered when equipment, materials, work processes or other relevant conditions change.
Common Mistakes When Applying the Hierarchy of Controls
Starting With PPE
Selecting PPE immediately without first considering whether the hazard can be eliminated, substituted or controlled at its source can miss stronger control opportunities.
Treating the Hierarchy as a Checklist
The hierarchy supports decision-making. Control selection still requires understanding the actual hazard, work activity and exposure conditions.
Failing to Review Controls
A control that was initially effective may become inadequate because of deterioration, process changes or new information.
The Hierarchy of Controls Supports Prevention at the Source
The hierarchy of controls provides a practical framework for moving beyond reactive safety measures. It encourages organizations to consider eliminating hazards first, then substitution and engineering solutions before relying primarily on administrative measures or personal protective equipment.
Control decisions should remain appropriate to the specific hazard, workplace and applicable legal or regulatory requirements. Once controls are implemented, their effectiveness should be monitored and reviewed.
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