Hierarchy of Controls for Chemical Hazards

The hierarchy of controls is a ranked system for reducing workplace hazards, ordered from most to least effective: elimination, substitution, engineering controls, administrative controls and personal protective equipment (PPE). For chemical hazards, it means removing or replacing a hazardous product before relying on ventilation, work procedures or PPE to limit exposure.

What is the hierarchy of controls?

The hierarchy of controls is a decision framework for choosing how to protect workers from a hazard. It tells you to start with the controls that remove or reduce the hazard at its source, and to move down to controls that depend on worker behaviour only when the higher levels are not feasible or not enough.

The framework is recognized internationally. The U.S. National Institute for Occupational Safety and Health (NIOSH) publishes the widely used inverted-triangle graphic, the Canadian Centre for Occupational Health and Safety (CCOHS) teaches the same ranking, and ISO 45001, the international standard for occupational health and safety management systems, requires organizations to eliminate hazards and reduce risks using the hierarchy of controls as part of operational planning and control. Many national and regional occupational health and safety regulations apply the same order of preference.

The hierarchy is usually drawn as an inverted triangle. The wide top represents the most effective controls, which protect everyone and do not depend on anyone remembering a rule. The narrow bottom represents the least effective controls, which protect only the person using them, and only when used correctly every time.

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 PPE.

1. Elimination: physically remove the chemical hazard from the workplace.
2. Substitution: replace the chemical or process with a less hazardous one.
3. Engineering controls: isolate people from the hazard or remove the contaminant before it reaches them.
4. Administrative controls: change how, when and by whom the work is done to reduce exposure.
5. Personal protective equipment (PPE): protect the individual worker with gloves, eye and face protection, protective clothing or respirators.

How does the hierarchy of controls apply to chemical hazards?

For chemicals, the hierarchy is applied product by product and task by task: identify the hazards from the safety data sheet (SDS), assess how workers are exposed, then work down the hierarchy to choose controls. Most chemical tasks end up with a combination of controls from several levels.

Elimination

Elimination removes the chemical, or the task that uses it, so the hazard no longer exists. It can happen before a product arrives, by declining to approve it for purchase, or afterwards, by removing it from inventory. Elimination is easiest at the design stage of a project or process, when changing the method costs the least. A chemical approval process is one practical way to apply elimination at the point of purchase, because every new product is reviewed before it reaches the worksite.

Substitution

Substitution replaces a hazardous chemical with one that has lower health and physical hazards, or changes the form of a product so it releases less contaminant. Examples include switching from a solvent-based to a water-based degreaser, using a product with a higher flash point, or buying a material as a paste or pellet instead of a dust. A substitute must be checked to confirm it does not introduce a different hazard and that it still does the job.

Products that a facility manufactures usually cannot be eliminated or substituted, although additives and process chemicals sometimes can. Shop supplies such as lubricants, cleaners, degreasers, paints and solvents are often the easiest candidates. Chemscape’s chemical substitution support compares the hazards of current products against alternatives to help identify safer options.

Engineering controls

Engineering controls reduce exposure by changing the work environment, and they protect workers without depending on their actions. For chemical hazards, they fall into three broad groups:

• Isolation and enclosure: keeping the chemical inside a closed system or away from people, such as sealed process equipment, closed transfer systems for drums and totes, glove boxes, or a separate room for a hazardous process.
• Local exhaust ventilation (LEV): capturing contaminants at or near the source, before they reach the worker’s breathing zone, and exhausting the contaminant outside or through an air-cleaning device. A capture hood at a mixing station or a ventilated weigh enclosure are common examples.
• General (dilution) ventilation: supplying and exhausting air across a whole room to lower the average concentration of a contaminant. It is suitable only for contaminants of low toxicity released in small, steady amounts, because it dilutes the contaminant rather than removing it from the worker’s breathing zone. Natural ventilation through doors and windows is the least controllable form.

Well-designed engineering controls need regular inspection and maintenance. For example, an LEV system’s airflow should be measured periodically to confirm it still captures the contaminant.

Administrative controls

Administrative controls are work practices that reduce the duration, frequency and severity of exposure. They are normally used alongside other controls rather than on their own. Common administrative controls for chemicals include:

• Chemical safety policies and safe work procedures
• Restricting access to areas where hazardous chemicals are used or stored
• Scheduling high-exposure tasks when fewer people are present, or rotating workers
• Housekeeping and decontamination procedures
• Hazard communication labels, signage and SDS access
• Training on the hazards and on the controls in place
• Exposure and health monitoring
• Alarms and warning systems

Personal protective equipment

PPE includes chemical-resistant gloves, eye and face protection, protective clothing and respirators. It is the final level of the hierarchy because it protects only the wearer, and only when the right equipment is selected, fitted, worn and maintained correctly. Respirators, for example, require the correct cartridge for the contaminant and fit testing to confirm a seal.

What is the most effective control? What is the least effective?

Elimination is the most effective control because a chemical that is not in the workplace cannot harm anyone. PPE is the least effective control because it leaves the hazard in place and depends entirely on correct selection and consistent use.

Administrative controls and PPE share a weakness: both rely on people following rules every time. When a procedure is inconvenient or equipment is uncomfortable, shortcuts become more likely, and protection drops. Controls higher in the hierarchy remove that dependency.

Why is PPE the last line of defence?

PPE is the last line of defence because it does nothing to reduce the hazard itself. If a glove is the wrong material, a respirator is poorly fitted, or equipment is removed for a moment, the worker is exposed. PPE is still essential where higher-level controls cannot reduce exposure enough, during emergencies, and while better controls are being put in place, but it should not be the first choice. Read more about the limitations of PPE as a hazard control method and best practices for selecting and using PPE.

How do you implement the hierarchy of controls for chemicals?

Implementing the hierarchy means following a repeatable process for every chemical and task, documenting the decisions, and checking that the chosen controls keep working.

1. Build a complete chemical inventory. You cannot control what you do not know is on site. Keep an up-to-date SDS for every product.
2. Identify the hazards. Use SDS Section 2 (hazard identification), Section 8 (exposure controls and personal protection) and Section 11 (toxicological information).
3. Assess exposure and risk. Consider how the chemical is used, how much, how often, and by whom. A chemical risk assessment prioritizes the products and tasks that need attention first.
4. Work down the hierarchy. Ask whether the chemical can be eliminated, then substituted, before moving to engineering controls, administrative controls and PPE. Record why a higher control was not feasible.
5. Select and implement controls. Most tasks use a combination. Control recommendations for chemical use translate the hazard and risk assessment into specific measures.
6. Monitor and review. Confirm that the controls work in practice (see below), and repeat the process when a product, process or regulation changes.

Chemscape’s CHAMP chemical management platform brings these steps together, combining SDS management, chemical approvals, risk assessments, substitutions and control recommendations, with industrial hygiene support available for specialist questions.

Monitoring and reviewing control effectiveness

A control only protects workers if it continues to work. Effectiveness can be checked by:

• Measuring workplace exposures and comparing them to the applicable occupational exposure limits (OELs) for each substance
• Inspecting and testing engineering controls, such as LEV airflow measurements
• Auditing whether procedures are followed and PPE is used and maintained correctly
• Reviewing incidents, near misses and health surveillance results
• Re-assessing whenever a new product, process, piece of equipment or regulatory limit is introduced

Involving workers in control selection

Workers who handle chemicals every day often know where exposures really happen and which controls will be practical. Involving them in identifying hazards, trialling substitutes and choosing controls improves the fit of the controls and makes it more likely they will be used. ISO 45001 also requires consultation and participation of workers in determining and applying controls.

Frequently Asked Questions

What is the difference between engineering and administrative controls?

Engineering controls change the workplace itself, for example by enclosing a process or capturing contaminants with local exhaust ventilation, so they protect workers without relying on their behaviour. Administrative controls change how people work, such as procedures, access restrictions or scheduling, so they only work when people follow them. That is why engineering controls rank higher in the hierarchy.

Can you use more than one control at a time?

Yes. Most chemical tasks use a combination of controls from several levels. For example, a mixing operation might use a less hazardous substitute, local exhaust ventilation at the mixing vessel, a written procedure and chemical-resistant gloves. The hierarchy guides which controls to prioritize, not a requirement to pick only one.

Is PPE ever the right first choice?

PPE can be the appropriate immediate measure in emergencies, for short-duration or non-routine tasks where higher-level controls are not practical, or as interim protection while better controls are installed. It should not be the default long-term solution where elimination, substitution, engineering or administrative controls are feasible.

How do you find a safer chemical substitute?

Start by defining what the product needs to do, then compare candidate products using their SDSs, looking at health hazards, physical hazards such as flammability, and exposure limits. Trial the substitute on a small scale to confirm it performs and does not create new hazards. Specialist chemical substitution support can speed up the comparison.

Where does the SDS fit into choosing controls?

The SDS is the starting point. Section 2 identifies the hazards, Section 8 lists exposure limits and recommended controls and PPE, and Section 11 describes health effects. The SDS gives you the information to assess risk, but controls still need to be chosen for the way the chemical is actually used at your site.

Who created the hierarchy of controls?

No single person or organization is credited with inventing the hierarchy of controls; it developed within occupational safety and industrial hygiene practice over many decades. NIOSH is the source of the widely used inverted-triangle graphic, and organizations such as CCOHS and ISO 45001 apply the same ranking today.

Put the hierarchy of controls into practice with CHAMP

CHAMP (Chemical Hazard Assessment Management Program) helps EHS teams apply the hierarchy of controls across their chemical inventory: approving or rejecting new products before they arrive, identifying substitutes, assessing risk, and recommending controls, all built on accurate SDS management and supported by industrial hygiene expertise.