The hierarchy of controls, applied on site

The hierarchy of controls is the single most useful idea in practical risk management. It ranks the ways you can control a hazard by how reliably they work — not by how cheap or convenient they are. The order matters because the controls at the top remove human behaviour from the equation, and the controls at the bottom depend on a person doing the right thing every single time.

The levels

From most effective to least:

1. Elimination — remove the hazard entirely. Design the task so no one has to work at height at all.
2. Substitution — replace the hazard with something less dangerous. Swap a solvent for a water-based alternative.
3. Isolation — separate people from the hazard. Guard, barricade, or lock out the energy source.
4. Engineering controls — design the risk down. Fixed edge protection, ventilation, interlocks.
5. Administrative controls — change how people work. Procedures, permits, training, signage, job rotation.
6. PPE — protect the individual as the last line. Harnesses, respirators, gloves.

The Australian WHS model names all six levels explicitly, calling out isolation as its own step. The widely used NIOSH version folds isolation into engineering controls and lists five. The principle is identical: work down the list, and only rely on the lower levels once the higher ones are genuinely not reasonably practicable.

Why order beats convenience

Elimination and substitution change the work so the hazard is simply not there. Isolation and engineering controls remove the hazard from the person by design — they keep working whether or not anyone is paying attention. Administrative controls and PPE are different in kind: they only work if a human does the right thing, in the right way, at the right moment — every time. That is why they are the least reliable, and why “we wrote a procedure” or “we issued PPE” is rarely a complete answer to a serious risk.

This is also the trap the hierarchy is designed to expose. Under time pressure it is tempting to reach for the cheapest control — a toolbox talk and a sign — because it is fast. The hierarchy is the discipline that asks: could we have engineered this out instead?

Using the hierarchy in the loop

The hierarchy is not just a poster for your risk assessments — it should shape what happens across the whole HSE system:

• In bowtie analysis, prefer critical controls that sit high in the hierarchy; a fatal risk protected only by PPE and procedure is fragile.
• In ICAM investigations, push recommendations up the hierarchy instead of defaulting to “retrain the worker”.
• In corrective actions, record which level of control an action delivers, so you can see whether you are genuinely reducing risk or just adding paperwork.

Contego carries the hierarchy of controls through the connected loop, so the control you choose in a risk assessment is the control an investigation and an audit later hold you to. Book a walkthrough.