Hierarchy of Controls in WHS: From Elimination to PPE

Why the Hierarchy of Controls Matters in WHS Law

The hierarchy of controls is embedded in both the WHS Regulations and the reasonably practicable assessment required by section 18 of the WHS Act. When assessing whether a duty holder took all reasonably practicable steps to eliminate or minimise a risk, a WHS expert witness works through the hierarchy from top to bottom, assessing what was available and practicable at each level before moving to the next.

A duty holder who goes straight to PPE without considering elimination, substitution or engineering controls has almost certainly failed to meet the reasonably practicable standard where higher-order controls were available. Conversely, where genuine engineering solutions were not technically feasible, the analysis will reflect that and assess the adequacy of the administrative controls and PPE that were used instead.

The Six Levels of the Hierarchy

Level 1: Elimination

The most effective control is to eliminate the hazard entirely. If work at height is dangerous, redesigning the work so it can be performed at ground level eliminates the fall risk. If a chemical is toxic, reformulating the product to remove the toxic ingredient eliminates the exposure risk. Elimination is always the preferred option and should be considered first.

Level 2: Substitution

Where elimination is not practicable, the hazardous item or process can be substituted for a less hazardous one. Substituting a toxic solvent for a water-based alternative, or replacing a manual lifting task with a mechanical lifting device, reduces the risk even if it does not eliminate it entirely.

Level 3: Engineering Controls

Engineering controls physically change the workplace or the work process to reduce exposure to the hazard. Machine guarding, ventilation systems, edge protection and interlocks are all engineering controls. They are preferred over administrative controls because they do not rely on worker behaviour to be effective.

Level 4: Isolation

Isolation separates people from the hazard. Exclusion zones around plant, enclosures around noise sources, and lockout procedures that isolate energy sources before maintenance work are all isolation controls. Isolation is sometimes grouped with engineering controls in the WHS Regulations.

Level 5: Administrative Controls

Administrative controls change the way people work. Safe Work Method Statements, job rotation to limit exposure time, training and supervision are all administrative controls. They are less reliable than engineering controls because they depend on workers consistently following procedures, which training and supervision alone cannot guarantee.

Level 6: Personal Protective Equipment (PPE)

PPE is the last resort, not the first line of defence. Gloves, respirators, hearing protection and safety harnesses protect the individual from the hazard but do not reduce the hazard itself. Where engineering controls would have eliminated or reduced the risk but were not used, reliance on PPE is unlikely to satisfy the reasonably practicable standard.

How the Hierarchy Applies in Expert Witness Analysis

When a WHS expert witness assesses whether a duty holder took reasonably practicable steps, the hierarchy of controls provides the analytical framework. Starting at the top of the hierarchy, the expert assesses whether each level of control was considered, whether it was technically and practically feasible, and whether the cost would have been grossly disproportionate to the risk. Where a higher-order control was available, suitable and not grossly expensive, the failure to implement it is a failure to meet the reasonably practicable standard.

This framework underpins the breach analysis service and is applied across all incident types from falls from height to machinery and plant incidents. See also reasonably practicable explained for the full section 18 framework.