Hierarchy of controls

Controlling exposures to occupational hazards is the fundamental method of protecting workers. 

Traditionally, a hierarchy of controls has been used to determine how to implement feasible and effective control solutions.

In the event of nonroutine work or emergencies, a control to an exposure could fail, thereby leaving an employee exposed to a hazard. 

When you layer the controls from top to bottom (most effective to least effective), the redundancies work together to control the hazard in the case anyone control fails. Be sure to follow up on implemented controls to ensure their effectiveness and to help maintain a safe work environment. 

  • 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

Most effective control method to reduce hazards.

Design or development stage processes: Elimination and substitutions of hazards may be inexpensive and simple to implement. 

Existing processes: Major changes in equipment and procedures may be required to eliminate or substitute for a hazard.

NIOSH leads a national initiative called Prevention through Design (PtD) to prevent or reduce occupational injuries, illnesses, and fatalities through the inclusion of prevention considerations in all designs that impact workers. The hierarchy of controls is a PtD strategy. To learn more, visit the PtD website.

Engineering controls

Designed to remove the hazard at the source.

Protecting workers: 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. 

Cost: Inexpensive to establish but, over the longer term, can be very costly to sustain.

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