Hierarchy of controls

According to The National Institute for Occupational Safety and Health (NIOSH),

Controlling exposures to hazards in the workplace is vital to protecting workers. The hierarchy of controls is a way of determining which actions will best to control those exposures. The hierarchy of controls has five levels of actions to reduce or remove hazards. The preferred order of action based on general effectiveness is:

  1. Elimination
  2. Substitution
  3. Engineering controls
  4. Administrative controls
  5. Personal protective equipment (PPE)

Using this hierarchy can lower worker exposures and reduce risk of illness or injury.


The idea behind this hierarchy is that the control methods at the top of the graphic are potentially more effective and protective than those at the bottom. Following this hierarchy normally leads to the implementation of inherently safer systems, where the risk of illness or injury has been substantially reduced.

Elimination and substitution

Elimination removes the hazard at the source by changing the work process so no exposure can occur while substitution is selecting a safer alternative to the source of the hazard. Elimination or substitution at the process development stage can provide lasting and cost effective solutions.

NIOSH leads a national initiative called Prevention through Design (PtD). Prevention through Design is the concept of “designing out” or minimizing hazards and risks before they are added to the process.

Effectiveness: Elimination and substitution are the most effective control methods to reduce hazards.

Cost: Elimination and substitutions of hazards may be inexpensive and simple to implement in the design or development stage. Major changes in equipment and procedures in existing processes may be required to eliminate or substitute for a hazard.

Engineering controls

Engineering controls can include modifying equipment or the workspace, using protective barriers, ventilation, and more. The NIOSH Engineering Controls Database has examples of published engineering control research findings.

Effectiveness: Engineering controls will typically be independent of worker interactions to provide this high level of protection. 

Cost: Over the longer term, operating costs are frequently lower and, in some instances, can provide cost savings in other areas of the process.

Administrative controls and PPE

Frequently used with existing processes where hazards are not particularly well controlled. According to NIOSH, employers should not rely on PPE alone to control hazards when other effective control options are available. PPE can be effective, but only when workers use it correctly and consistently.

Effectiveness: Have proven to be less effective than other measures, requiring significant effort by the affected workers and their supervisors.

Cost: Both PPE and administrative controls are inexpensive to establish but, over the longer term, PPE can be very costly to sustain.