The hierarchy of controls

The hierarchy of controls is a ranked list of ways to deal with a hazard: eliminate it, substitute something less dangerous, engineer it out, manage it with procedures, and only then rely on personal protective equipment. The higher a control sits, the less it depends on people doing the right thing every time. Most Canadian OHS laws expect employers to work down the list in that order.

The five levels

Each level answers the same question in a different way: how do we stop this hazard from hurting someone?

1. Elimination. Remove the hazard entirely. Bring the work down to the ground instead of working at height, or stop using a chemical the process no longer needs.
2. Substitution. Replace the hazard with something less harmful. A water-based coating instead of a solvent-based one, or a smaller, lighter container that is easier to lift.
3. Engineering controls. Physically separate people from the hazard. Machine guards, guardrails, local exhaust ventilation, interlocks, sound enclosures and lifting aids all fit here.
4. Administrative controls. Change the way people work. Written procedures, permits, training, signage, job rotation, scheduling and supervision.
5. Personal protective equipment (PPE). Equipment worn by the worker, such as respirators, hearing protection, gloves, harnesses and safety eyewear.

The order matters because reliability drops as you move down. A guardrail protects everyone who walks past it, whether they are paying attention or not. A harness only protects the person wearing it, if it fits, if it is inspected, if it is connected to a suitable anchor, and if a rescue plan exists.

What the law expects

Provincial OHS laws in Alberta, British Columbia and Ontario all require employers to assess hazards and control them. Alberta's OHS Code is explicit: hazards are to be eliminated where reasonably practicable, and where that is not possible they are controlled using engineering controls, then administrative controls, then PPE, or a combination. British Columbia's OHS Regulation and Ontario's framework set out similar expectations, though the wording and structure differ. Check the current version of your province's rules, and any industry-specific requirements that apply to your work.

Management system standards such as CSA Z45001 (the Canadian adoption of ISO 45001) also build the hierarchy into how hazards are handled.

Applying it to a real hazard

Take a maintenance crew that cleans a dusty process area with compressed air and brooms once a week. A quick walk down the hierarchy might look like this:

• Eliminate: can the process change so less dust is produced or released in the first place?
• Substitute: use a vacuum fitted with a suitable filter instead of dry sweeping and blowing dust into the air.
• Engineer: add or repair dust collection at the source, enclose the transfer point that generates most of the dust.
• Administer: schedule cleaning when fewer people are in the area, train the crew on the method, post the procedure.
• PPE: provide respirators selected for the contaminant, with fit testing and a respiratory protection program behind them.

In practice you usually end up with a combination. The aim is to push as much of the risk reduction as possible into the upper levels so that the lower ones are a backstop rather than the main defence.

Common mistakes

Starting at the bottom

PPE is quick to buy and easy to document, so it is often the first answer. That is the wrong way round. If a hazard assessment lists only PPE as the control, ask what was considered higher up and why it was ruled out.

Treating training as a control on its own

Training is necessary, but it does not stop an exposure by itself. A trained worker beside an unguarded shaft is still beside an unguarded shaft.

Forgetting the new hazards a control creates

A guard that has to be removed for routine cleaning invites people to leave it off. A new enclosure may create a confined space. Every control needs a second look for side effects. This is where a proper hazard assessment earns its keep.

Not checking that controls still work

Ventilation fans fail, interlocks get bypassed, procedures drift. Build inspection and maintenance of controls into your program, and review them after any incident or change.

Where it shows up elsewhere

The same logic appears in many specific programs. The fall protection hierarchy ranks guardrails above travel restraint and fall arrest. Lockout is an administrative control backed by engineered isolation points. Respirators and hearing protection sit at the bottom of their respective programs for good reason.

How ehZee can help

ehZee's safety programs practice works with employers to review hazard assessments and check that the controls chosen follow the hierarchy and are realistic for the site. We start by asking why you need the program and what the work actually involves. See safety program development and review for how that works.

Common questions