The hierarchy of control procedure is a systematic method used to eliminate or reduce workplace hazards, ranked from most to least effective: elimination, substitution, engineering controls, administrative controls, and personal protective equipment (PPE). It is a legal and practical framework that requires employers to work through the levels in order, applying the highest feasible control before moving to lower ones.
Background and Purpose
The hierarchy of control is not a new idea—it has been a core principle of occupational health and safety (OHS) for decades. Its purpose is to prevent injuries, illnesses, and fatalities by addressing hazards at their source rather than relying on workers to protect themselves. The five levels are often drawn as an inverted pyramid, with elimination at the top (broadest impact) and PPE at the bottom (least reliable).
Why this order? Because controls higher up are more effective because they don’t depend on human behavior. For example, elimination removes the hazard entirely, so there is nothing to manage. In contrast, PPE requires the worker to wear it correctly, maintain it, and use it every time—a weak link. The procedure is designed to push decision-makers toward the strongest solution, not the cheapest or easiest one.
The Five Levels Explained
Each level has a distinct role. Here is what they mean in practice:
- Elimination: Remove the hazard completely. Example: stop using a toxic chemical in a process, or physically remove a trip hazard from a walkway.
- Substitution: Replace the hazard with something less dangerous. Example: use a water-based paint instead of a solvent-based one, or use a quieter machine.
- Engineering controls: Isolate people from the hazard through design or physical changes. Examples: machine guards, ventilation systems, noise enclosures, or interlock switches.
- Administrative controls: Change how people work through rules, training, signs, or schedules. Examples: rotating shifts to reduce exposure, written safe work procedures, or warning signs.
- PPE: Provide protective equipment such as gloves, respirators, hard hats, or safety glasses. This is the last line of defense, not the first.
In many jurisdictions, the hierarchy is legally mandated. For instance, OSHA in the United States and similar bodies in Australia, Canada, and the UK require employers to follow this order when controlling hazards. Failure to do so can result in citations and fines.
How to Apply the Procedure Step by Step
Implementing the hierarchy is not a one-time event—it is a process. Here is a typical step-by-step procedure:
- Identify the hazard: Walk through the workplace, talk to workers, review incident reports, and check safety data sheets.
- Assess the risk: Determine how likely an incident is and how severe it could be. This helps prioritize.
- Start at the top: Ask, “Can we eliminate the hazard?” If yes, do it. If not, move to substitution.
- Work down the levels: For each level, ask if it is feasible. Engineering controls often require investment, but they are more reliable than administrative ones.
- Combine controls if needed: Sometimes a single control isn’t enough. For example, you might substitute a chemical and also provide PPE for residual risk.
- Implement and document: Put the controls in place, update procedures, and train workers.
- Monitor and review: Check that controls work as intended. If a new hazard emerges or a control fails, revisit the hierarchy.
This process should be repeated whenever there is a significant change—new equipment, new substances, or after an incident.
How to Choose the Right Control Level
Choosing the right level is not always straightforward. The guiding principle is to use the highest level that is reasonably practicable. “Reasonably practicable” means weighing the cost and effort against the risk reduction. A small business might not afford a full engineering solution, but it must still do everything that is feasible before falling back on PPE.
Consider a concrete example: a factory that uses a noisy press. The hierarchy would suggest:
- Elimination: Can we stop using the press? Probably not if it’s essential.
- Substitution: Can we buy a quieter press? Maybe, but costly.
- Engineering: Can we enclose the press in a soundproof booth? This is often the practical choice.
- Administrative: Can we limit time near the press? Yes, but that doesn’t reduce noise at the source.
- PPE: Earplugs are the last resort, but they only protect the worker, not others nearby.
The decision should be documented, showing why a higher level was not chosen. This is crucial for legal compliance and for demonstrating due diligence.
Common Problems and Misconceptions
One major misconception is that PPE is the first thing to buy. In reality, it’s the last. Another is that administrative controls are “good enough”—but they rely on people remembering to follow rules, which is unreliable. A third is that the hierarchy is a one-way street: once you pick a control, you never revisit it. In fact, you should regularly review and improve.
Another issue is “control stacking”—using multiple lower-level controls instead of one higher-level one. For example, instead of eliminating a hazardous chemical, a company might require workers to wear respirators and take rotation breaks. That is not equivalent to elimination. The hierarchy explicitly prefers the higher level, even if it costs more upfront.
Finally, a common problem is that employers skip the hierarchy and go straight to what is cheapest. That is a legal and ethical failure. The procedure exists to force a disciplined, top-down approach.
Hierarchy vs. Other Safety Models
The hierarchy is often compared to other safety frameworks, such as the Swiss Cheese Model or the Plan-Do-Check-Act cycle. The Swiss Cheese Model focuses on multiple layers of defense, but it doesn’t rank them. The hierarchy is unique because it explicitly ranks effectiveness. The Plan-Do-Check-Act cycle is a broader management process that can incorporate the hierarchy as the “Do” step.
Another related concept is “risk assessment”—the process of evaluating hazards. The hierarchy is not a risk assessment itself, but it is the action plan that follows one. You first assess, then apply the hierarchy to control.
Costs, Benefits, and Realistic Expectations
Implementing higher-level controls often requires upfront investment. Engineering controls like ventilation or machine guards can be expensive. However, they reduce long-term costs from injuries, lost productivity, insurance premiums, and legal fees. Substitution might mean finding a new supplier or changing a recipe, which takes time.
Administrative controls are usually cheap but require ongoing training and enforcement. PPE is also cheap initially but has recurring costs for replacement and maintenance. The most cost-effective approach is often a combination: invest in engineering controls for the main risk, then use administrative and PPE for residual risk.
It’s important to set realistic expectations. No control is 100% effective. Even elimination can introduce new hazards (e.g., a new process). The goal is to reduce risk to as low as reasonably practicable, not to zero.
Template for a Hierarchy of Control Plan
| Hazard | Risk Description | Elimination Feasible? | Substitution Feasible? | Engineering Control | Admin Control | PPE | Selected Control | Review Date |
|---|---|---|---|---|---|---|---|---|
Sample (fictional): Hazard: solvent fumes. Risk: respiratory irritation. Elimination: No. Substitution: water-based cleaner. Engineering: local exhaust. Admin: training. PPE: respirator. Selected: substitution + exhaust. Review: 2025-03-01.
Frequently Asked Questions
Why is PPE at the bottom of the hierarchy?
Because PPE is the least reliable. It fails if worn incorrectly, gets damaged, or is forgotten. Higher-level controls protect everyone without requiring individual action.
Can I use more than one control at once?
Yes, and often you should. The hierarchy is not a “pick one” system. It’s a priority order. You should implement the highest feasible control, and then add lower-level controls to address any remaining risk.
What if my employer only gives me PPE?
That may be a violation if a higher control is feasible. You should raise the concern with your supervisor, safety representative, or the regulatory authority. Document the hazard and what you asked for.
Is the hierarchy legally required everywhere?
In most industrialized countries, yes, either explicitly or in practice. OSHA in the US, the HSE in the UK, and similar bodies in Australia and Canada all expect employers to follow this order. Check your local regulations for specifics.
How often should I review my controls?
At least annually, or whenever there is a change in process, equipment, or personnel. Also after any incident or near miss. Regular review is part of continuous improvement.
What is the difference between substitution and engineering controls?
Substitution replaces the hazard with a less dangerous one (e.g., a safer chemical). Engineering controls modify the environment or equipment to reduce exposure (e.g., a ventilation system). Substitution changes what you use; engineering changes how you use it.