The hierarchy of controls is a step-by-step approach to eliminating or reducing workplace hazards. It ranks controls from the most effective level of protection to the least effective level of protection.
When choosing a control method, start from the top of the inverted pyramid. Assess the feasibility of the first layer of controls (elimination) before moving onto the second layer (substitution). Continue this process until you reach of the bottom of the pyramid and have identified as many controls as needed to that will adequately protect the worker from the hazard.
Some sources may use a variation of this hierarchy of controls. Regardless of the number of layers included, the hierarchy should be considered in the order presented, so it is always best to try to eliminate the hazard first, etc.
Physically remove the hazard
Elimination is the process of removing the hazard from the workplace. It is the most effective way to control a risk because the hazard is no longer present. It is the preferred way to control a hazard and should be used whenever possible.
Examples of elimination control methods include:
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If eliminating a hazard is not possible, substitution is the next best control method that should be considered.
Substitution is act of replacing something with another thing… in this case, a hazard is replaced with a less hazardous one. The hazards and risks associated with an alternative must be thoroughly assessed to determine if it is an appropriate replacement. Care must be taken to make sure that the new hazard is actually lower, and that one hazard is not being replaced with another that is just as harmful or more harmful.
Examples of substitution controls include:
| Instead of: | Consider: |
|---|---|
|
carbon tetrachloride (causes liver damage, cancer) |
trichloroethane, dichloromethane |
|
benzene (causes cancer) |
toluene, cyclohexane, ketones |
|
pesticides (causes various effects on body) |
“natural” pesticides such as pyrethrins
|
|
organic solvents (causes various effects on body) |
water-detergent solutions |
|
leaded glazes, paints, pigments (causes various effects on body) |
versions that do not contain lead
|
|
sandstone grinding wheels (causes severe respiratory illness due to silica) |
synthetic grinding wheels such as aluminium oxide |
Remember, however, that you need to make sure the substitute product will not cause any harmful effects, and to control and monitor exposures to make sure that the replacement product is below occupational exposure limits.
Another type of substitution includes using the same chemical but to use it in a different form. For example, a dry, dusty powder may be a significant inhalation hazard but if this material can be purchased and used as pellets or crystals, there may be less dust in the air and therefore less exposure.
Engineering controls are methods that will remove the hazard at the source, before it comes in contact with the worker.
Engineering controls can be built into the design of a plant, equipment, or process to minimise the hazard. Engineering controls are a very reliable way to control worker exposures as long as the controls are designed, used, and maintained properly. Examples of engineering controls are:
Process control involves changing the way a job activity or process is done to reduce the risk. Monitoring should be done before and as well as after the change is implemented to make sure the changes did, in fact, control the hazard.
Examples of process changes include to:
These methods aim to keep the chemical “in” and the worker “out” (or vice versa).
An enclosure keeps a selected hazard “physically” away from the worker. Enclosed equipment, for example, is tightly sealed and it is typically only opened for cleaning or maintenance. Other examples include “glove boxes” (where a chemical is in a ventilated and enclosed space and the employee works with the material by using gloves that are built in), abrasive blasting cabinets, or remote control devices. Care must be taken when the enclosure is opened for maintenance as exposure could occur if adequate precautions are not taken. The enclosure itself must be well maintained to prevent leaks.
Isolation places the hazardous process “geographically” away from the majority of the workers. Common isolation techniques are to create a contaminant-free or noise-free booth either around the equipment or around the employee workstations.
Ventilation is a method of control that “adds” and “removes” air in the work environment. General or dilution ventilation can remove or dilute an air contaminant if designed properly. Local exhaust ventilation is designed to remove the contaminant at the source so it cannot disperse into the work space and it generally uses lower exhaust rates than general ventilation (general ventilation usually exchanges air in the entire room).
Local exhaust ventilation is an effective means of controlling hazardous exposures but should be used when other methods (such as elimination or substitution) are not possible.
The design of a ventilation system is very important and must match the particular process and product in use. Expert guidance should be sought. It is a very effective control measure but only if it is designed, tested, and maintained properly.
Because products are exhausted to the outdoors, you should also check with your local environment agency or authority for any environmental air regulations that may apply in your area.
Administrative controls involve developing procedures to ensure the work conducted in a way that minimises the hazard. Examples include developing or changing policies, implementing or improving training and education, and developing or enhancing work practices and procedures.
Administrative controls are ranked lower than elimination, substitution, and engineering controls because this method does not necessarily remove or reduce the hazard from the workplace. For example, administrative controls limit workers’ exposures by scheduling shorter work times in contaminant areas or by implementing other “rules”. These control measures have many limitations because the hazard itself is not actually removed or reduced. Administrative controls should be used in combination with other control measures where possible.
Methods of administrative control include:
More information about types of administrative controls is provided below:
Elements of safe work practices include:
Employee education and training on how to conduct their work safely is a critical element of any complete workplace health and safety program. Training must cover not only how to do the job safely but it must also ensure that workers understand the hazards and risks of their job, and the controls in place to protect them. It must also provide them with information on how to protect themselves and co-workers.
Good housekeeping is essential to prevent the accumulation of hazardous or toxic materials (e.g., build-up of dust or contaminant on ledges, or beams), or hazardous conditions (e.g., poor storage).
Being prepare for emergencies means making sure that the necessary equipment and supplies are readily available and that employees know what to do when something unplanned happens such as a release, spill, fire, or injury. These procedures should be written and employees should have the opportunity to practice their emergency response skills regularly.
Personal hygiene practices are another effective way to reduce the amount of a hazardous material absorbed, ingested, or inhaled by a worker.
Examples of personal hygiene practices include:
Personal protective equipment (PPE) refers to anything workers wear to help protect them from a workplace hazard.
The use of PPE as the main method to control exposures should be limited to situations where elimination, substitution, engineering, or administrative controls are not practicable, or when:
PPE limits exposure to the harmful effects of a hazard but only if the PPE is worn and used correctly. Examples of PPE include:
The choice of what type of PPE is required must be based on the specific hazard found at the workplace. No matter which type of PPE is used, it is essential to have a complete PPE program in place.
The short answer is yes. The longer; sometimes a hazard cannot be controlled using a single type of control method. If a hazard cannot be eliminated, a combination of controls may be required.
For example:
Yes. It is important to determine the effectiveness of the control methods implemented and adjust as required.
Controls must not create new hazards. For example, if wearing PPE contributes to other hazards (e.g., heat stress), then it is important to review if other controls methods are possible or if additional precautions are needed.
Monitor both the hazard and the control method to make sure that the control is working effectively and that exposure to the hazard is reduced or eliminated. Consider the following questions:
When progressing through the Hierarchy of Controls, take time and proximity into account, to control hazards, rather than later.
Regarding proximity: Be aware that toward the top of the hierarchy, the objective is to control the source of the hazard. Toward the bottom, the goal is to protect the worker and/or others from potential harm.
Additionally, controls are either passive or active. At the top of the hierarchy, a worker won’t need to play a role to help control the hazard, but will need to become more of an active participant further down the hierarchy. “Even with engineering controls, some of them require more actions by the workers and the management than others, whether it’s filter changes, maintenance inspections or just flipping switches.
The more actions needed, the more the “must trust” factor comes into play. For example, employers will have to trust workers to wear PPE correctly every time, while workers will have to trust that their employer will provide the proper PPE. The further you go up on the hierarchy, reliance on or trust in sometime fallible people is less of a factor.
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Trying to determine which control methods to use? Along with using the hierarchy to “identify and evaluate options,” employers should:
If necessary, use interim controls until long-term solutions are put in place.
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