Hierarchy of Controls

The hierarchy of controls is a ranked framework for reducing workplace hazards, ordered from most to least effective: elimination, substitution, engineering controls, administrative controls and personal protective equipment (PPE). Safety professionals use it to choose controls that remove or reduce a hazard at its source before relying on worker behavior or protective gear.

The framework is promoted by NIOSH, referenced throughout OSHA guidance, and built into management system standards such as ISO 45001. It is one of the most widely used decision tools in occupational safety.

What Is the Hierarchy of Controls?

According to NIOSH's hierarchy of controls guidance, the five levels are:

1. Elimination: physically removing the hazard at its source. NIOSH describes this as the preferred option because no exposure can occur.
2. Substitution: replacing the source of the hazard with a safer alternative. Substitutes should be checked for new hazards they may introduce.
3. Engineering controls: isolating people from the hazard or reducing contact through equipment design, barriers, enclosures or ventilation.
4. Administrative controls: changing the way people work to reduce the duration, frequency or intensity of exposure, such as procedures, training, job rotation and limiting access.
5. Personal protective equipment: gear worn by the worker, such as gloves, respirators or hearing protection.

NIOSH explains that the top three levels are more effective because they control exposure without depending heavily on human action. Administrative controls and PPE require ongoing effort from workers and supervisors. NIOSH also states that employers should not rely on PPE alone when other effective controls are available.

ISO 45001, clause 8.1.2, requires organizations to eliminate hazards and reduce occupational health and safety risks using a similar hierarchy: eliminate the hazard, substitute with less hazardous processes or materials, use engineering controls and reorganize work, use administrative controls including training, and use adequate PPE.

Why the Hierarchy of Controls Matters

Controls at the top of the hierarchy work every time without anyone remembering to follow a rule. A guard that is built into a machine protects the operator on the night shift, on a rushed day and when a new hire is still learning. A rule that says "keep hands clear" only works when it is followed.

The hierarchy also gives safety teams a consistent way to evaluate options and explain decisions. When a risk assessment or job hazard analysis identifies a hazard, the hierarchy prompts the team to ask whether the hazard can be removed before settling for a procedure or PPE. Many OSHA standards follow the same logic. For example, several health standards require feasible engineering and work practice controls before respirators are used.

The Five Levels Explained With Examples

Elimination

Elimination removes the hazard entirely. Examples include lowering equipment to ground level so no one works at height, prefabricating components on the ground instead of at height, or removing a manual lifting task by having materials delivered on pallets to the point of use. Elimination is easiest during design or planning, when changes cost less.

Substitution

Substitution replaces a hazard with something less dangerous. Common examples are switching from a solvent-based cleaner to a water-based one, using a lower-voltage tool, or buying materials in smaller, lighter packages. Always review the substitute's safety data sheet, since it may have different hazards.

Engineering Controls

Engineering controls separate workers from the hazard. Examples include local exhaust ventilation at a welding station, machine guarding and interlocks, noise enclosures, guardrails, and lift assists. Engineering controls usually cost more upfront but reduce reliance on behavior.

Administrative Controls

Administrative controls change how work is done. They include written procedures, lockout/tagout programs, permits, warning signs, training, scheduling hot tasks in cooler hours, and job rotation to limit exposure time. They are often necessary, but they depend on people following them consistently.

Personal Protective Equipment

Personal protective equipment is the last line of defense. It includes safety glasses, gloves, respirators, hearing protection and fall arrest harnesses. PPE only protects when it is properly selected, fitted, maintained and worn every time, and it does nothing to reduce the hazard itself.

How to Apply the Hierarchy of Controls Step by Step

1. Identify the hazard. Use inspections, observations, incident data and job hazard analyses to find hazards and the tasks that create exposure.
2. Assess the risk. Estimate how likely and how severe harm could be, so you know which hazards to address first.
3. Start at the top. For each hazard, ask whether it can be eliminated. If not, ask whether a safer substitute exists, then move down the hierarchy.
4. Combine controls where needed. Most real-world solutions layer several levels, such as an engineering control backed by a procedure and PPE.
5. Check for new hazards. Confirm that a new control does not create a different risk, such as a guard that blocks visibility.
6. Implement and assign owners. Give each control an owner and a due date, and use interim controls while permanent fixes are put in place.
7. Verify effectiveness. Monitor exposure, inspect the control and talk to workers to confirm it works as intended.

Worked Example

Consider a hypothetical maintenance shop where technicians clean parts by hand with a solvent that causes skin irritation and vapor exposure. The team works through the hierarchy:

• Elimination: Could parts arrive pre-cleaned from the supplier? In this case, no.
• Substitution: Switch to a water-based degreaser with fewer hazards. Adopted for most parts.
• Engineering: Install an enclosed parts washer with local exhaust for parts that still need solvent.
• Administrative: Update the procedure, train technicians and limit solvent use to the enclosed washer.
• PPE: Provide chemical-resistant gloves and eye protection for loading and unloading.

The result is a layered solution where PPE is still used, but it is no longer the primary control.

Hierarchy of Controls vs. Risk Assessment

A risk assessment and the hierarchy of controls are complementary. The risk assessment identifies hazards and ranks risks. The hierarchy of controls guides what to do about each risk. A good assessment records the control chosen at each level, the reason higher-level options were not feasible, and the residual risk that remains after controls are applied.

Common Mistakes to Avoid

• Jumping straight to PPE. PPE is quick to issue, but it should follow a genuine review of higher-level options.
• Treating training as the fix. Training supports controls, but it rarely removes a hazard on its own.
• Ignoring cost over time. Engineering controls can be cheaper over the life of a task than ongoing PPE, training and supervision.
• Not verifying. A control that is installed but bypassed or poorly maintained provides little protection.
• Skipping worker input. The people who do the task often know what will work and what will be bypassed.

How SMS360 Helps

The SMS360 Risk Assessment module lets teams record hazards, rate risks and document the controls selected at each level of the hierarchy. Assessments can be assigned, reviewed and updated from a mobile device, and follow-up actions can be tracked with owners and due dates. Dashboards help safety managers see which risks still rely mainly on administrative controls or PPE and where higher-level controls are planned.

Frequently Asked Questions

What are the 5 levels of the hierarchy of controls?

The five levels, from most to least effective, are elimination, substitution, engineering controls, administrative controls and personal protective equipment. Elimination and substitution remove or replace the hazard. Engineering controls isolate people from it. Administrative controls change how people work, and PPE protects the individual worker. Higher levels are preferred because they rely less on human behavior.

Why is PPE the least effective control?

PPE does not reduce the hazard itself. It only places a barrier between the hazard and the person wearing it. If the equipment is the wrong type, fits poorly, is damaged or is not worn, the worker is fully exposed. PPE also depends on training, supervision and maintenance, which makes it vulnerable to human error and inconsistent use.

Is the hierarchy of controls required by OSHA?

No single OSHA rule requires the hierarchy of controls for every hazard, but OSHA guidance recommends it, and several standards require feasible engineering and work practice controls before relying on respirators or other PPE. ISO 45001, clause 8.1.2, also requires organizations to apply a hierarchy when eliminating hazards and reducing risks.

Can you use more than one level of control at a time?

Yes, and most effective solutions do. A common approach is to install an engineering control, support it with a written procedure and training, and provide PPE for remaining exposure. Layering controls adds protection if one control fails. The goal is to make sure the strongest feasible control does most of the work.