Introduction to the Hierarchy of Hazard Control
Identifying and controlling safety and health hazards in the workplace is fundamental to the prevention of injuries and illnesses. Many different techniques are available to help identify hazards, such as workplace audits, supervisor observation, job safety analysis and injury claims analysis. The hierarchy of hazard control is a system used to minimize or eliminate worker exposure to hazards.
When workplace hazards are identified, organizations often look for a quick fix, such as providing additional training or personal protective equipment (PPE). While these may be appropriate controls for some hazards, other control techniques—beginning with elimination—should be investigated. The hierarchy of hazard control, in order of effectiveness, is as follows:
- Elimination: removing the hazard from the workplace
- Substitution: replacing a hazardous substance or activity with a less hazardous one
- Engineering Controls: isolating workers from the hazard (e.g. providing machine guards)
- Administrative Controls: developing policies and procedures for safe work practices
- PPE: providing and requiring the use of safety devices such as respirators, earplugs, hard hats and safety glasses
Eliminate the Hazard
When evaluating the best way to control a hazard, start at the top of the hierarchy. Elimination of a hazard is the most effective means of controlling it. Where no hazard or exposure exists, no chance of injury or illness exists.
There are many ways to eliminate a hazard from the workplace. For example, consider the hazard of an operator repetitively placing metal parts into a press. Over time, the operator may develop cumulative trauma disorders from repetitive use of the hands and wrists. By automating the press so operators do not have to handle the parts, the hazard of repetition is eliminated. Other examples of hazard elimination include:
- Redesign a workstation to relieve physical stress and remove ergonomic hazards
- Install a sound absorbing enclosure around a noisy machine
- Remove trip hazards in pedestrian walkways
Substitution: Replacing the Hazard with Something Less Hazardous
If it's not feasible to eliminate a hazard, the next most effective approach is substitution. For example, consider the case of stripping the floor finish from a terrazzo floor so new finish can be applied. The current method uses an extremely corrosive product known to cause chemical burns to exposed skin. In addition, the slippery residue produced by the stripping process creates a slip and fall hazard. The organization should investigate alternative processes such as a dry removal process that does not use chemicals, eliminating the chemical exposure and slip and fall hazards.
Other examples of hazard substitution include:
- Replace a larger parts container (70 lb capacity) with a smaller parts container (20 lb capacity) to reduce the risk of overexertion
- Replace a pesticide that is a known carcinogen with a natural pesticide
The third most effective approach is to reduce the hazard at its source. Engineering controls are a very reliable way to control worker exposures as long as the controls are designed, used and maintained properly.
Engineering controls do not eliminate hazards. Instead, they keep people isolated from them. For example, consider a road crew that is exposed to high levels of dust when cutting concrete. Since there is no way to eliminate or substitute the dust hazard, the road crew uses a wet method to keep airborne dust to a minimum.
Other examples of engineering controls include:
- Ensuring that proper machine guarding is in place on all machinery and equipment
- Using mechanical aids (lift tables, hoists, etc.) to minimize material handling injuries
- Using ventilation to remove fumes and vapors at their source
- Providing adjustable workstations to accommodate employees of different heights
Administrative controls are management strategies or procedures designed to reduce employee exposure to hazards by changing the way people work. Administrative controls do not actually remove or reduce the hazard and should only be used when elimination, substitution and engineering controls are infeasible or cannot be implemented immediately.
For example, consider our previous case of an operator placing metal parts into a press. If automation is not possible, the next best option might be to rotate operators every two hours, so no single worker is using their hands and wrists constantly throughout the shift. As you can see, this option does not reduce or eliminate the hazard, but it reduces the worker's exposure to the hazard.
Other examples of administrative controls include:
- Training employees on safe job procedures
- Using team lifts for heavy parts
- Requiring workers in hot environments to take breaks and providing fluids for rehydration
- Installing warning signs and labels on equipment
- Performing maintenance involving hazardous materials at night when minimal staff is present
Personal Protective Equipment
PPE should only be used after all other steps in the hierarchy have been investigated. PPE is the least effective means of controlling hazards because of the high potential for the PPE to become ineffective due to damage or negligence.
There are many types of PPE available for controlling hazards such as noise, chemical exposure and sharp objects. In many cases, PPE is used to supplement the existing engineering and administrative controls.
For example, a lathe protected by a Plexiglas shield can reduce the amount of flying metal chips, but likely will not completely reduce the risk of a chip entering the operator's eye. To supplement the shield, safety glasses should also be used.
Other examples of PPE use include:
- Wearing earplugs or earmuffs in noisy areas
- Wearing gloves to prevent cuts and splinters
- Wearing a hard hat on a construction job site
Start at the Top of the Hierarchy of Hazard Control
It's important to remember to always start at the top and work your way down the hierarchy. The goal is always to eliminate the hazard or replace it with something less hazardous when possible.
Unfortunately, engineering controls can be avoided by employees, administrative controls rely on reading and comprehending the training or signage, and PPE requires employees to correctly use the equipment—making them less effective solutions.
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