The hierarchy of controls

The hierarchy of controls is the most useful single framework in H&S. It ranks types of control measure by their effectiveness — and the rank is more or less the inverse of how often they’re used.

This page explains the hierarchy and how to apply it when you’re adding controls to a hazard.

The hierarchy

Rank	Control type	What it does
1	Eliminate	Remove the hazard entirely.
2	Substitute	Replace with something less hazardous.
3	Isolate	Separate people from the hazard.
4	Engineering	A physical change that reduces exposure.
5	Administrative	A change to procedures or training.
6	PPE	Personal protective equipment.

Rank 1 is the most effective; rank 6 is the least. The principle in HSWA: aim as high up the hierarchy as is reasonably practicable.

Why the order matters

Higher-ranked controls don’t depend on people doing the right thing.

Elimination is unconditional. If the hazard is gone, no human error can bring it back.
PPE is entirely conditional. It only helps when worn, correctly, every time, by everyone — and most workers, most days, fall short of “every time, perfectly”.

Engineering controls (a guard on a saw, a barrier rail, an extraction fan) generally don’t fail. Administrative controls (a procedure, a training course, a sign) work only when people follow them. PPE works only when they wear it correctly. These are not equivalent strategies for the same problem.

Applied examples

Slip on wet floor

Rank	Possible control
1 Eliminate	Replace mopping with sweep + vacuum (no wet floors).
2 Substitute	Use a dry-spec cleaning compound.
3 Isolate	Cone off the area; restrict pedestrian access during cleaning.
4 Engineering	Install non-slip flooring.
5 Administrative	Wet floor signs + cleaning procedure.
6 PPE	Issue non-slip footwear.

A common workplace combines several: non-slip flooring (4) + cleaning procedure (5) + non-slip shoes (6). That’s defensible. A workplace with only the cleaning procedure and a sign is leaning heavily on rank 5 — and that’s where slip incidents tend to come from.

Chemical exposure

Rank	Possible control
1 Eliminate	Switch process so the chemical isn’t needed.
2 Substitute	Use a less toxic alternative.
3 Isolate	Enclose the process; remote operation.
4 Engineering	Local exhaust ventilation.
5 Administrative	Decant procedures; safe-handling training.
6 PPE	Respirators, gloves, eye protection.

How to apply this in SteadyOn

When you fill in a hazard’s Control measures field, organise your text by hierarchy level. Even a one-line marker per level —

Engineering: extraction fan rated 1500m³/hr
Administrative: SDS sheet displayed; refresher annually
PPE: nitrile gloves; respirators where exposure exceeds X

— makes it obvious at a glance whether your defences are spread properly. A control text that’s all PPE is a flag. A control text that has elimination at the top is a brag worth keeping.

When you raise an action to add a new control, aim higher up the hierarchy than what’s currently in place. Replacing a procedure with a barrier (5 → 3) is a step up; adding more PPE (6 → 6) often isn’t.

SFAIRP and “as far as reasonably practicable”

NZ law doesn’t require you to apply rank 1 to every hazard. It requires you to apply controls so far as is reasonably practicable (SFAIRP). That means:

High-severity hazards warrant rank-1 or rank-2 controls — even if they cost more.
Lower-severity hazards may only justify administrative or PPE controls.

The matrix sets the bar; the hierarchy gives you the menu.