Hierarchy of Controls Explained

Last updated: March 2026 | Reading time: 10 min

The Hierarchy of Controls is one of the most important concepts in workplace health and safety, and it appears frequently on the White Card assessment. This guide explains each level of the hierarchy with practical construction examples so you can apply the concept confidently.

What Is the Hierarchy of Controls?

The Hierarchy of Controls is a systematic approach to eliminating or reducing workplace hazards. It ranks control measures from most effective (elimination) to least effective (personal protective equipment). The principle is simple: always start at the top and work downward. Only move to a lower-level control when higher-level options are not reasonably practicable.

The hierarchy is embedded in Australian WHS legislation. Section 17 of the Work Health and Safety Act 2011 requires duty holders to eliminate risks so far as is reasonably practicable, and if elimination is not reasonably practicable, to minimise risks so far as is reasonably practicable using the hierarchy.

The Six Levels of the Hierarchy

Level 1: Elimination (Most Effective)

Elimination completely removes the hazard from the workplace. It is the most effective control because if the hazard does not exist, it cannot cause harm. This should always be the first option considered.

Construction Examples:

• Prefabricating wall frames at ground level rather than building them at height — this eliminates the fall hazard entirely
• Designing a building without a need for manual excavation near underground services
• Using pre-cast concrete panels instead of pouring concrete in formwork at height
• Eliminating the need for hot work by using mechanical fasteners instead of welding

Elimination is not always possible, especially on construction sites where hazards are inherent in the work. When elimination is not reasonably practicable, move to the next level.

Level 2: Substitution

Substitution involves replacing a hazardous substance, process, or equipment with something less hazardous. The hazard still exists but is significantly reduced.

Construction Examples:

• Using water-based paint instead of solvent-based paint to reduce toxic fume exposure
• Replacing a noisy pneumatic tool with a quieter electric alternative
• Using pre-mixed concrete instead of mixing on-site (reduces dust and manual handling)
• Substituting a toxic cleaning chemical with a less hazardous biodegradable product
• Using fibreglass ladders instead of aluminium near electrical work

Level 3: Isolation

Isolation separates the hazard from people by distance or a physical barrier. The hazard remains but workers are physically prevented from coming into contact with it.

Construction Examples:

• Installing guardrails around open edges and excavations to prevent falls
• Enclosing a noisy generator inside an acoustic barrier
• Fencing off an asbestos removal area to prevent unauthorised access
• Using lockout/tagout to isolate electrical energy during maintenance
• Setting up exclusion zones around crane operations

Level 4: Engineering Controls

Engineering controls physically change the workplace or the equipment to reduce risk. They do not eliminate the hazard but make it less likely to cause harm.

Construction Examples:

• Installing local exhaust ventilation to capture dust from cutting operations
• Using mechanical lifting aids (forklifts, hoists) to reduce manual handling
• Installing edge protection systems on scaffolding
• Using water suppression on concrete saws to reduce silica dust
• Installing residual current devices (RCDs) on all electrical circuits
• Providing vibration-dampened handles on power tools

Level 5: Administrative Controls

Administrative controls are work practices, procedures, training, and signage that reduce the risk of harm. They rely on human behaviour, which makes them less reliable than physical controls.

Construction Examples:

• Safe Work Method Statements (SWMS) for high-risk construction work
• Job rotation to reduce repetitive strain and vibration exposure
• Safety inductions and toolbox talks
• Speed limits for vehicles and forklifts on site
• Warning signs and hazard labels
• Scheduling noisy work during times when fewer workers are present
• Permit-to-work systems for confined space entry and hot work

Level 6: Personal Protective Equipment (PPE) — Least Effective

PPE is the last resort in the hierarchy. It protects individual workers but does not reduce or eliminate the hazard itself. PPE relies on correct selection, fit, use, and maintenance, which makes it the least reliable control.

Construction Examples:

• Hard hats to protect against falling objects
• Safety boots with steel or composite toe caps
• Hi-vis clothing for visibility
• Safety glasses and goggles for eye protection
• Hearing protection (earplugs or earmuffs) for noise exposure
• Respiratory protection (P2 masks) for dust and fume exposure
• Full-body harnesses as fall arrest systems

Why the Order Matters

The hierarchy is ordered by effectiveness and reliability. Controls at the top (elimination, substitution) are inherently more reliable because they remove or reduce the hazard at the source. Controls at the bottom (administrative, PPE) rely on human behaviour, which is subject to error, complacency, and non-compliance.

For example, consider the risk of silica dust from cutting concrete:

• Elimination: Use pre-cut concrete panels (no cutting needed on site)
• Substitution: Use a material that does not contain silica
• Engineering: Use a wet-cutting method with water suppression and local exhaust ventilation
• Administrative: Limit cutting time, train workers on dust hazards, monitor air quality
• PPE: Provide P2 respirators (last resort, relies on correct fit and consistent use)

In practice, multiple controls from different levels are often combined for the best protection. This is called "defence in depth."

Hierarchy of Controls on the White Card Test

The White Card test frequently asks questions about the hierarchy. Common question types include:

• "What is the most effective control measure?" — Answer: Elimination
• "What is the least effective control?" — Answer: PPE
• "Which is an example of an engineering control?" — Look for physical modifications
• "Which is an example of substitution?" — Look for replacing something hazardous with something less hazardous
• "Why is PPE considered the last resort?" — Because it does not reduce the hazard and relies on correct use

Key Takeaways

• Always start at the top of the hierarchy (elimination) and work down
• Higher-level controls are more effective and reliable than lower-level ones
• PPE should never be the primary control — it is the last resort
• Multiple controls from different levels can be combined for better protection
• The hierarchy is embedded in WHS legislation under "reasonably practicable"
• Understanding the hierarchy is essential for passing the White Card test