Hierarchy of Controls

What is meant by hierarchy of controls?

The hierarchy of controls refers to determining how to implement feasible and effective means for controlling employee exposure to workplace hazards. There are four types of controls used to control employee exposure to hazards, listed in the order of effectiveness:

  • Elimination or substitution

  • Engineering controls

  • Administrative and work practice controls

  • Personal protective equipment (including respiratory protection)

Hierarchy of Controls

Tab/Accordion Items

What is elimination?

Elimination refers to the removal of hazards from a process or procedure.

What is substitution?

Substitution refers to the use of safer alternatives (equipment, chemicals) to ones currently being used in a process or procedure.

Both measures require action by the employer to remove the hazards before worker exposure can occur and are the most effective type of controls. However when substituting, for example, one chemical in a process or procedure for another, be sure that the substituted chemical does not introduce new or additional hazards to the workplace.

What are engineering controls?

Engineering controls result in a physical change to the workplace made by the employer, which eliminates or reduces the hazard associated with a job or task. 

Examples include general dilution ventilation, local exhaust ventilation, isolating the worker from the process, and enclosing the process. Where substitution or elimination of the source of the hazard(s) is not feasible, engineering controls are the most effective means of controlling employee exposure.

Regarding the use of engineering controls for flammable gases and vapors, the engineering controls (e.g., ventilation) must not only reduce levels to meet the lower explosive (or flammability) limit, but must also be sufficient to reduce exposures to the permissible exposure limit(s) for the chemicals involved.

What are administrative and work practice controls?

Administrative and work practice controls establish efficient procedures for accomplishing a task and require either or both the employer and the worker to take some action.

Examples include lockout/tagout, job rotation and adjusting work schedules to reduce employee exposures, hygiene practices such as handwashing, and prompt cleanup of toxic dusts using HEPA vacuums.


What is personal protective equipment?

Personal protective equipment (PPE) is specialized clothing or equipment worn by an employee for protection against a hazard. PPE is used when engineering controls and administrative and work practice controls have been fully implemented and a hazard remains.

Examples of PPE include hard hats, chemical resistant gloves, and respirators.

Because the use of PPE requires the employee to wear something for protection against a hazard, it should never be regarded as the sole means of protecting the employee against a hazard.

More information on PPE can be found on the A-Z safety and health topics page for personal protective equipment and respiratory protection.