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The Hierarchy of Control: Why Engineering Controls Do the Heavy Lifting on Australian Sites

Best Practice

The hierarchy of control is the order you work through when you deal with a hazard on site. You start with the most effective option, which is removing the hazard altogether, and you only move down to the next level when the one above is not reasonably practicable. Personal protective equipment sits at the bottom, as the last line of defence.

There are six levels, from most effective to least effective:

Eliminate. Remove the hazard so it is not there at all.
Substitute. Swap it for something less dangerous.
Isolate. Keep people away from it, using distance, barriers or enclosures.
Engineering controls. Use equipment that removes or reduces the hazard at source.
Administrative controls. Change how the work is done, through procedures, rotas, training and signage.
Personal protective equipment. Respirators, hearing protection, eye protection and gloves for whatever risk is left.

Australian work health and safety law expects you to work down this list from the top, and to be able to show why a higher level was not reasonably practicable before you relied on a lower one.

On a live construction, infrastructure or industrial site, engineering controls are usually where the biggest practical gains are made. This guide takes you through:

What each level looks like on a real site
Where the law fits in, in plain terms
Why engineering controls do so much of the work once a job is running
Engineering controls for dust, fume, noise and ventilation in practice
How to keep your controls working, and the common mistakes to avoid

Step 1. Know what each level looks like on site

Elimination

The hazard is removed completely. This is usually a planning decision rather than something done on the tools. Ordering materials cut to size means no cutting happens on site, so there is no cutting dust. Using battery or mains powered plant inside a building means there is no diesel exhaust.

Substitution

The hazard is replaced with something that carries less risk. A water based product instead of a solvent based one, a zero silica board instead of a high silica one, or a quieter machine instead of whichever one happened to be in the yard. Check the replacement for new hazards, so the problem is reduced rather than simply moved.

Isolation

People are separated from the hazard. A screened cutting station away from other trades, an acoustic enclosure around a generator, or an exclusion zone during breaking out.

Engineering controls

Equipment that deals with the hazard at source, without relying on anyone changing how they work. Dust extraction on the tool, local exhaust ventilation at the weld, silencers and acoustic screens on noisy plant, and fans and ducting that move contaminated air out of an enclosed space.

Administrative controls

Changes to how the work is organised. Safe work method statements, job rotation to limit any one person's exposure, restricted access, signage and training.

Personal protective equipment

Equipment worn by the individual worker. It is still needed in most real situations, because some risk usually remains after the higher levels have been applied. It works best as the final layer of protection rather than the first.

Step 2. Understand where the law fits

Under the model Work Health and Safety Regulations, regulation 35 requires a person conducting a business or undertaking to manage risks to health and safety, and regulation 36 sets out the order described above.

In practice, that means two things. If a hazard can reasonably be eliminated, it should be. If it cannot, the risk should be reduced as far as is reasonably practicable using substitution, isolation or engineering controls, with administrative controls and personal protective equipment covering what remains.

Regulations 37 and 38 add that controls must be maintained so they keep working, and reviewed when something changes. Step 8 covers what that means day to day.

Step 3. Recognise why engineering controls do the heavy lifting

Elimination and substitution are the most effective levels, but most of those decisions are made at design and tender stage. Once the programme is running, the materials are ordered, the method is set and the plant is on site. Isolation helps, but on an occupied building or a busy corridor there is often limited room to separate people from the work.

That leaves engineering controls as the level where a site team can make the biggest difference day to day. They have three clear advantages over the levels below them:

They deal with the hazard at source, so everyone in the area is protected, not just the operator.
They keep working when nobody is watching, because they do not depend on people following a procedure or wearing equipment correctly.
Their performance can be measured, so you can show a client, a principal contractor or a regulator that the control is doing its job.

Step 4. Control dust at the source

Cutting, grinding, drilling and breaking out concrete, masonry and stone all produce respirable dust, much of it containing crystalline silica. Effective engineering controls include:

On tool extraction fitted to grinders, saws and drills, capturing dust at the point it is created
Water suppression at the blade to stop dust becoming airborne
H class vacuums for clean up, instead of dry sweeping or compressed air
Negative pressure units that keep dust inside the work area and stop it reaching other parts of the building

Step 5. Control fume and diesel exhaust

Welding fume and diesel exhaust build up quickly in basements, tunnels, plant rooms and partly enclosed structures. Effective engineering controls include:

Local exhaust ventilation that captures weld fume at the arc, before it reaches the welder's breathing zone
Extraction that takes exhaust away from the working position and out of the space
Forced air ventilation that brings clean air in so contaminants cannot accumulate

Step 6. Control noise at the machine

Hearing protection only protects the person wearing it. Reducing noise at the plant itself protects everyone nearby. Effective engineering controls include:

Acoustic enclosures around generators, compressors and pumps
Silencers and damping fitted to the machine
Acoustic screens and barriers between the work and the people around it
Noise monitoring to confirm the controls are bringing levels down where people are working

Step 7. Ventilate enclosed spaces properly

Good ventilation supports every other control in an enclosed space. It works best when the fans and ducting are sized for the space and the task, and the airflow follows a planned route, with contaminated air drawn out and clean air brought in, rather than simply being moved around the room.

Step 8. Keep the controls working

An engineering control only protects people while it is working properly. A blocked filter, a crushed duct or a switched off unit can stop it doing its job without anyone noticing. Regulation 37 makes maintenance a duty in its own right.

Good practice is to:

Check and maintain equipment on a set schedule, including filters, ducting and seals
Use air and noise monitoring to confirm that exposure is actually coming down
Review the controls whenever the task, the plant, the materials or the layout change, as regulation 38 requires

Step 9. Back it up with administrative controls and PPE

Once the engineering controls are in place, administrative controls and personal protective equipment manage the risk that is left. Restricted access, timed operations and job rotation reduce how long people are exposed. A fit tested respirator and the right hearing protection give the operator a final layer of protection.

Common mistakes to avoid

Starting at the bottom. Masks and earplugs are quick to hand out, which is why they are often the first response rather than the last.
Treating the list as a menu. It is an order to work through, with a test of what is reasonably practicable at each level.
Confusing monitoring with control. Measuring exposure shows whether a control works. It does not reduce exposure on its own.
Installing a control and forgetting it. Equipment that is not maintained stops protecting people.

Applying it to a real task

Application Example:Concrete cutting on an occupied site.

Elimination means ordering pre cut units so the cut does not happen.
Substitution means a saw with integrated water suppression instead of a dry blade.
Isolation means a screened cutting station away from other trades.
Engineering controls mean on tool extraction, an H class vacuum and a negative pressure unit.
Administrative controls mean restricted access, timed operations and rotation.
Personal protective equipment means a fit tested respirator and hearing protection for the operator.

Each level reduces the exposure a little further, and on a job like this the engineering controls do most of that work.

Getting it right on your site

Working out which controls are reasonably practicable for your task, your space and your programme is a site specific exercise. RVT Group Australia supplies engineering controls on hire for dust, fume, noise and ventilation across construction, infrastructure and industrial projects. Every hire starts with a site assessment, so the equipment is specified around the hazard, the space and the programme.

Book a free site assessment and demonstration, or call the team on 1300 086 248.

The model WHS laws created by Safe Work Australia have been implemented by all jurisdictions except Victoria. Victoria is governed by the state-specific Occupational Health and Safety Act 2004 and its own set of occupational health and safety regulations. Western Australia adopted the model laws with its own regulation numbering.