Hierarchy of hazard controls



Hierarchy of hazard control is a system used in industry to prioritize possible interventions to minimize or eliminate exposure to hazards. It is a widely accepted system promoted by numerous safety organizations. This concept is taught to managers in industry, to be promoted as standard practice in the workplace. It has also been used to inform public policy, in fields such as road safety. Various illustrations are used to depict this system, most commonly a triangle.

The hazard controls in the hierarchy are, in order of decreasing priority: The system is not based on evidence about effectiveness but based on If elimination of the hazard is possible, it frees workers of being aware of the hazard and protecting themselves. Substitution has less priority than elimination because the substitute can possibly also come with a hazard. Engineering controls depend on a well-functioning system and human behaviour. Administrative controls and personal protective equipment are always dependent on human behaviour which makes these controls less reliable.
 * Elimination
 * Substitution
 * Engineering controls
 * Administrative controls
 * Personal protective equipment

History


During the 1990s TB outbreak, resulting from the HIV epidemic in the United States, the hierarchy of controls was described as a way for healthcare workers to mitigate their exposure to TB. Starting from page 10, the hierarchy can be summarized, from most to least preferable, like this:
 * "Substitution" - Avoids the hazard, which is not possible in a healthcare setting.
 * "Contain [the hazards] at their source" - Using administrative controls, screen for a given health hazard (in this case, TB).
 * This can include source control, which can involve masking an infected patient.
 * "Engineering controls" - This usually involves configuring isolation rooms and HVAC systems to prevent the spread of infection.
 * "Establish barriers" - Personal protective equipment, with respirators.

Today's hierarchy is similar, with a few differences:

Elimination
Physical removal of the hazard is the most effective hazard control. For example, if employees must work high above the ground, the hazard can be eliminated by moving the piece they are working on to ground level to eliminate the need to work at heights. However, often elimination of the hazard is not possible because the task explicitly involves handling a hazardous agent. For example in health care when treating patients with infectious diseases, exposure to the infectious agent is not possible to eliminate. The same holds for removing asbestos where handling the hazardous agent is the core of the task.

Substitution


Substitution, the second most effective hazard control, involves replacing something that produces a hazard with something that does not produce a hazard or produces a lesser hazard—for example, replacing solvent-based paint with water-based paint. To be an effective control, the new product must not produce unintended consequences. Because airborne dust can be hazardous, if a product can be purchased with a larger particle size, the smaller product may effectively be substituted with the larger product.

Engineering controls
The third most effective means of controlling hazards is engineered controls. These do not eliminate hazards, but rather isolate people from hazards. Capital costs of engineered controls tend to be higher than less effective controls in the hierarchy, however they may reduce future costs. For example, a crew might build a work platform rather than purchase, replace, and maintain fall arrest equipment. "Enclosure and isolation" creates a physical barrier between personnel and hazards, such as using remotely controlled equipment. Fume hoods can remove airborne contaminants as a means of engineered control.

Administrative controls
Administrative controls are changes to the way people work. Examples of administrative controls include procedure changes, employee training, and installation of signs and warning labels (such as those in the Workplace Hazardous Materials Information System). Administrative controls do not remove hazards, but limit or prevent people's exposure to the hazards, such as completing road construction at night when fewer people are driving.

Personal protective equipment
Personal protective equipment (PPE) includes gloves, Nomex clothing, overalls, Tyvek suits, respirators, hard hats, safety glasses, high-visibility clothing, and safety footwear. PPE is often the most important means of controlling hazards such as in health care and asbestos removal. Even though almost always also other prevention strategies are possible these do not reduce the risks to safe levels. PPE must then be used to still further reduce risks to safe levels. However, considerable efforts are needed to use PPE effectively such as training in donning and doffing or testing the equipment. Additionally, some PPE, such as respirators, increase physiological effort to complete a task and, therefore, may require medical examinations to ensure workers can use the PPE without risking their health.

Role in Prevention through Design
The hierarchy of controls is a core component of Prevention through Design, the concept of applying methods to minimize occupational hazards early in the design process. Prevention through Design emphasizes addressing hazards at the top of the hierarchy of controls (mainly through elimination and substitution) at the earliest stages of project development.

Variations on the NIOSH Control Hierarchy
While the control hierarchy shown above is traditionally used in the United States and Canada, other countries or entities may use a slightly different structure. In particular, some add isolation above engineering controls instead of combining the two. The variation of the hierarchy used in the ARECC decision-making framework and process for industrial hygiene (IH) includes modification of the material or procedure to reduce hazards or exposures (sometimes considered a subset of the hazard substitution option but explicitly considered there to mean that the efficacy of the modification for the situation at hand must be confirmed by the user). The ARECC version of the hierarchy also includes warnings as a distinct element to clarify the nature of the warning. In other systems, warnings are sometimes considered part of engineering controls and sometimes part of administrative controls.