What is the hierarchy of controls?
Short answer
The hierarchy of controls is a ranked sequence of risk-control approaches required under WHS / HSWA: 1) eliminate the hazard, 2) substitute it, 3) isolate it, 4) apply engineering controls, 5) apply administrative controls, 6) use PPE. PPE is the last resort, never the first.
The hierarchy of controls is the legally-mandated ranking of risk-control approaches under WHS Regulation (AU) reg. 36 and HSWA (NZ) s.17. It is read from most effective to least effective:
- Elimination — remove the hazard entirely (don't do the task; redesign so the hazard doesn't exist).
- Substitution — replace the hazard with a less hazardous one (substitute a less toxic chemical, use a lighter material).
- Isolation — separate the hazard from people (machine guards, exclusion zones, enclosures).
- Engineering controls — re-engineer the work to reduce exposure (ventilation, mechanical aids, automation).
- Administrative controls — change the way people work (procedures, training, signs, rotation).
- Personal Protective Equipment (PPE) — protect the individual person (respirators, gloves, hearing protection).
The legal duty is to apply controls as high up the hierarchy as is reasonably practicable. PPE is the last line of defence — it does nothing about the underlying hazard, it only protects the person if it's worn correctly, the right size, in date and not damaged.
A common audit failure is jumping straight to PPE without showing why elimination, substitution, isolation, engineering and administrative controls weren't reasonable. RAE IQ's risk assessment and SWMS / Site Safety Plan generators force the hierarchy: you can't skip levels without justification.