The Hierarchy of Controls: A Practical Guide for Australian Workplaces

The hierarchy of controls is a systematic framework for managing workplace risks, ranked from most effective to least effective. It is embedded in the WHS Regulation 2025 and referenced in every approved code of practice. The hierarchy requires duty holders to implement the highest-level control that is reasonably practicable before relying on lower-level controls. The five levels, from highest to lowest, are elimination, substitution, engineering controls (isolation), administrative controls, and personal protective equipment (PPE).

The hierarchy reflects a fundamental principle of occupational health and safety: controls that remove or reduce the hazard at its source are inherently more reliable than controls that depend on human behaviour. A ventilation system that captures welding fume at the source operates continuously without relying on each welder to wear a respirator correctly. A guarded machine prevents access to moving parts without relying on workers to remember safe work procedures. The hierarchy is not a menu from which you pick the most convenient option — it is a sequence that must be followed from top to bottom.

Elimination is the most effective control because it removes the hazard entirely. If you can eliminate a hazardous process, substance, or piece of equipment, the risk drops to zero for that hazard. Examples include designing out work at heights by assembling components at ground level, removing a hazardous chemical from the process entirely, or automating a manual handling task so no worker is exposed to the load.

Substitution replaces the hazard with something less hazardous. Replacing solvent-based paints with water-based alternatives reduces volatile organic compound exposure. Using diamond-tipped wet cutting instead of dry cutting on silica-containing materials reduces respirable crystalline silica generation by over 90 per cent. Substituting a less toxic cleaning chemical for a more toxic one reduces the severity of potential exposure. Substitution does not eliminate the risk but can reduce it dramatically. Both elimination and substitution should be considered at the design and procurement stage, as retrofitting these controls after a process is established is usually more expensive and disruptive.

Engineering controls modify the workplace, equipment, or process to reduce exposure without relying on worker behaviour. They include isolation (physically separating the hazard from workers), ventilation (local exhaust ventilation to capture contaminants at the source), guarding (preventing access to moving parts), and automation (removing the worker from the hazardous task). Engineering controls are the backbone of effective risk management for health hazards.

Local exhaust ventilation (LEV) is one of the most common engineering controls in Australian workplaces. A well-designed LEV system captures airborne contaminants — dust, fume, vapour, or mist — at the point of generation before they enter the worker's breathing zone. The WHS Regulation 2025 requires LEV systems to be maintained and tested to ensure they continue to operate at design specifications. For substances with workplace exposure limits that are tightening from December 2026, existing LEV systems may need to be upgraded to achieve lower capture concentrations. Engineering controls require capital investment but provide continuous protection over their operational life.

Administrative controls change the way work is organised or performed. They include safe work procedures, job rotation to limit exposure duration, scheduling hazardous work when fewer workers are present, training programs, signage, and permit-to-work systems. Administrative controls are less reliable than engineering controls because they depend on consistent human compliance.

However, administrative controls are essential where engineering controls alone cannot reduce risk to an acceptable level. A SWMS (Safe Work Method Statement) is an administrative control that documents the hazards, risks, and control measures for high-risk construction work. Training ensures workers understand the hazards they face and the controls in place. Health surveillance programs detect early signs of occupational disease before irreversible damage occurs. Job rotation limits the cumulative exposure of individual workers to a hazard — for example, rotating workers through a noisy area so no individual exceeds the 85 dB(A) daily exposure standard. Administrative controls should always supplement, not replace, higher-order controls.

PPE is the last line of defence in the hierarchy of controls. It includes respiratory protective equipment, hearing protection, eye protection, gloves, safety footwear, hard hats, and high-visibility clothing. PPE does not reduce the hazard — it creates a barrier between the hazard and the worker. If the barrier fails (a respirator seal leaks, earplugs are inserted incorrectly, gloves are not chemical-resistant), the worker is exposed to the full hazard.

The WHS Regulation 2025 requires PPE to be selected based on the nature of the hazard and the conditions of exposure, maintained in good working order, fitted and used correctly, and replaced when damaged or at the end of its service life. Respiratory protective equipment must be fit-tested to the individual wearer in accordance with AS/NZS 1715. PPE should only be relied upon as the primary control when higher-order controls are not reasonably practicable, or as an interim measure while engineering controls are being designed and installed. A workplace that relies primarily on PPE for hazard management is not meeting the intent of the hierarchy of controls.

Effective risk management almost always requires a combination of controls from multiple levels of the hierarchy. For a welding workshop, the approach might include substituting high-manganese welding wire with a lower-manganese alternative (substitution), installing local exhaust ventilation on each welding bay (engineering), implementing a safe work procedure for fume management (administrative), and providing P2 respirators for tasks where LEV alone cannot achieve exposure below the workplace exposure limit (PPE).

Document your control selection process in your risk assessment. For each hazard, record which levels of the hierarchy you considered, which controls you selected, and why higher-level controls were or were not reasonably practicable. This documentation demonstrates due diligence under section 27 of the WHS Act and provides evidence that you followed a systematic process. Review controls regularly — the WHS Regulation 2025 requires a review whenever there is a change in the work environment, a new hazard is identified, or monitoring results indicate that existing controls are not effective.