Course 600 - Introduction to Occupational Safety and Health

Safety guides and audits to make your job as a safety professional easier

Hazard Controls

As you learned earlier, there are many different types of hazards in the workplace. Hazardous conditions include unsafe materials, equipment, the environment, and employees. Unsafe work practices include: allowing untrained workers to perform hazardous tasks, taking unsafe shortcuts, horseplay, or long work schedules. To combat these hazardous conditions and unsafe work practices, control strategies referred to as the "Hierarchy of Controls" have been developed.

Traditionally, a hierarchy of controls, listed from most to least effective, has been used as a means of determining how to implement feasible and effective controls. ANSI Z10, Occupational Health and Safety Management Systems, encourages employers to employ the six hazard control strategies.

Caution asbestos hazard sign
ANSI Z10 Hierarchy of Controls
  1. Elimination. Totally eliminates the hazard. No hazard: no exposure.
  2. Substitution. Mitigates a hazard. Replaces toxics with non toxics.
  3. Engineering controls. Isolates hazards through design.
  4. Warnings. Alert employees to the hazard.
  5. Administrative controls. Safe procedures and practices.
  6. Personal protective equipment (PPE). Places a barrier between hazard and worker.

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

For more information on evaluating safety management systems, see OSHAcademy Course 716, Safety Management System Evaluation, and OSHAcademy's Ultimate Safety Management System Audit.

Let's take a closer look at the hierarchy of control strategies.

What are "feasible" controls?

Image of Feasibility
Controls must be technically and economically feasible.

Hazard abatement (reduction) measures required to prevent a hazard should be technologically and economically feasible (reasonable) for the employer. This means that the measures required to prevent a possible hazard should be 1) possible given currently available technology, and 2) financially reasonable.

OSHA uses the following criteria to determine the feasibility of hazard controls:

  • Technical Feasibility. Technical feasibility is the existence of technical know-how as to materials and methods available or adaptable to specific circumstances which can be applied with a reasonable possibility that employee exposure to hazards will be reduced.
  • Economic Feasibility. Economic feasibility means that the employer is financially able to undertake the measures necessary to abate identified hazards. Economic feasibility is a major issue to be considered when imposing hazard controls. OSHA may allow the use of PPE to abate a hazard, at least until engineering controls become a less significant economic burden for the company when the following conditions are met:
    1. If significant reconstruction of a single establishment involving a capital expenditure which would seriously jeopardize the financial condition of the company is the only method whereby the employer could achieve effective engineering controls;
    2. If there are no feasible administrative or work practice controls; and
    3. If adequate personal protective equipment or devices are available.

Elimination & Substitution

Elimination and substitution, while most effective at reducing hazards, also tend to be the most difficult to implement in an existing process. If the process is still at the design or development stage, elimination and substitution of hazards may be inexpensive and simple to implement. For an existing process, major changes in equipment and procedures may be required to eliminate or substitute for a hazard.

Safety professionals consider these strategies first because they can completely eliminate the hazard. Eliminating the hazard will also eliminate the possibility of exposure to the hazard.

What's the difference between the elimination and substitution methods?

When using elimination, the hazard is completely removed, making it impossible for an accident to occur. The hazard is not simply reduced, but it is completely eliminated.

When using substitution, the hazard is reduced or eliminated by using a less hazardous component. Although it is possible to eliminate the hazard, the substitution method does not necessarily eliminate the hazard. This is why the elimination is preferred over substitution.

Some examples of these two strategies include:

  • Eliminating the source of excessive temperatures, noise, or pressure
  • Substituting a toxic chemical with a less toxic or non-toxic chemical

Engineering Controls

Image of Feasibility
This circular saw is engineered to prevent injury.

The basic concept behind engineering control strategies is that, to the extent possible, tools, equipment, machinery, and work environment should be designed to eliminate or reduce exposure to hazards. While this approach is called engineering controls, it does not necessarily mean that an engineer is required to design the control.

Some examples of this strategy include:

  • Designing tools, equipment, and machines with guards to reduce exposure to hazardous moving parts,
  • Redesigning a work station to relieve physical stress and reduce ergonomic hazards,
  • Designing ventilation with sufficient fresh outdoor air to improve indoor air quality, and
  • Ensure adequate lighting is installed for the environment and tasks performed.
Image of Feasibility
Machine guards enclose hazardous moving parts.

Enclosure of Hazards

When you cannot remove a hazard or replace it with a less hazardous alternative, the next best control is enclosure. Enclosing a hazard usually means that there is no hazard exposure to workers during normal production operations.

There may be potential exposure to workers during maintenance operations or if the enclosure system breaks down. For those situations, additional controls such as safe work practices or personal protective equipment (PPE) may be necessary to control exposure.

Some examples of enclosure designs are:

  • Complete enclosure of moving parts of machinery with machine guards,
  • Complete containment of toxic liquids or gases from the beginning to end of a process,
  • Glove box operations to enclose work with dangerous microorganisms, radioisotopes, or toxic substances, or
  • Complete containment of noise, heat, or pressure producing processes with materials especially designed for those purposes.

Barriers or Local Ventilation

Image of Feasibility
Forced air ventilation for confined space entry.

When the potential hazard cannot be removed, replaced, or enclosed, the next best approach is a barrier to exposure or, in the case of air contaminants, local exhaust ventilation to remove the contaminant from the workplace.

This engineering control involves potential exposure to the worker even in normal operations. Consequently, it should be used only in conjunction with other types of controls, such as safe work practices designed specifically for the site condition and/or PPE. Examples include:

  • Ventilation hoods in spray booths,
  • Electronic sensor barriers,
  • Isolation of a process in an area away from workers,
  • Baffles used as noise-absorbing barriers, and
  • Nuclear radiation or heat shields.


With the release of ANSI Z10-2012, "warnings" have been promoted to their own hierarchy level. Previously they were considered part of administrative controls. Warnings do not prevent exposure to a hazard, but they do provide a visual or audible indicator to warn people of potential danger.

Image of Feasibility
Signs can be used to warn people of potential hazards.

Warnings can be either visual, audible, or both. They may also be tactile. Some examples of warnings are:

  • Visual. Signs, labels, tags, and flashing/strobe lights.
  • Audible. Alarms, bells, beepers, sirens, announcement system and horns.
  • Tactile. Vibration devices or air fans.

For instance, a door could have both a sign warning of a hazard as well as an alarm if opened. Warnings can be effective deterrents, but are not as effective as elimination, substitution, or engineering controls.

OSHA Signs

OSHA's 1910.145, Specifications for accident prevention signs and tags details the following types of signs:

  • Danger Signs - Signs that alert people to specific and immediate dangers (including radiation hazards).
  • Warning Signs - Signs that warn people of potential hazards that can lead to death.
  • Caution Signs - Signs used to alert people to potential hazards. This class can also be used to caution people against certain unsafe practices. This class is for hazards that can result in minor (non-life threatening) accident or injury.
  • Safety Instruction Signs - These signs offer instructions for how someone should act or perform to avoid possible hazards.

One potential problem when using warnings is the misinterpretation of the warning itself. Does the symbol or text clearly explain what the hazard is to the public? For example, if a sign only contains a written warning, someone might read the sign but not know what the warning actually means. Or, if an alarm sounds, what does the alarm mean? These are challenges when using warnings and why they are not as effective as higher-level controls.

Administrative Controls

Image of Feasibility
Administrative controls work only as long as workers behave.

Administrative controls are developed by management for the purpose of preventing or reducing exposure by controlling behaviors that may result in exposure to hazards. These controls are needed when hazards can't be adequately eliminated or mitigated through elimination, substitution, and engineering controls.

Administrative controls are policies, programs, processes, procedures, and practices that include the following examples:

  • Providing training for all hazardous tasks,
  • Developing safety procedures for all hazardous tasks,
  • Developing safety rules and guidelines for all work,
  • Developing suitable work schedules to reduce stress and fatigue, and
  • Creating safe work procedures and practices using job hazard analyses.

Be careful to distinguish rules from guidelines when developing administrative controls. It's important to understand that mandatory safety "rules" are required and must be followed. On the other hand, discretionary "guidelines" are voluntary. Safety managers may be justified when disciplining employees for non-compliance with rules, but they are not justified in disciplining if employees choose not to follow guidelines.

Ultimately, effective administrative controls are only as effective as the safety management system that supports them. It's always better to eliminate the hazard so that you don't have to rely on administrative controls that tend to work only if employees behave.

Administrative Controls (Continued)

Image of Feasibility
Administrative controls limit exposure through safe practices.

Safe work practices

Safe work practices may be quite specific or general.

In terms of scope, safe work practices may be a very important part of a single task or applicable to many jobs in the workplace. Here are some examples of safe work practices:

  • removing tripping, blocking, and slipping hazards,
  • wetting down surfaces to keep toxic dust out of the air,
  • using safe lifting techniques, and
  • maintaining equipment and tools in good repair.

Interim Measures

When a hazard is recognized, the preferred correction or control cannot always be accomplished immediately. OSHA believes there is always some kind of interim measure that can be used to temporarily abate a hazard. These can range from taping down wires that pose a tripping hazard to actually shutting down an operation temporarily.

The importance of taking these interim protective actions cannot be overemphasized. There is no way to predict when a hazard will cause serious harm, and no justification to continue exposing workers unnecessarily to risk.

Personal Protective Equipment (PPE)

Image of Man Wearing PPE
PPE is used in conjunction with other hazard controls.

When engineering, work practice and administrative controls are not feasible or do not provide sufficient protection, employers must provide PPE to their employees and ensure its use. PPE is actually used primarily in conjunction with other controls.

  • Eye and Face Protection. Safety glasses or face shields are worn any time work operations can cause foreign objects to get in the eye. For example, during welding, cutting, grinding, nailing (or when working with concrete and/or harmful chemicals or when exposed to flying particles). Wear when exposed to any electrical hazards, including working on energized electrical systems.
  • Eye and face protectors - select based on anticipated hazards.
  • Foot Protection. Construction workers should wear work shoes or boots with slip-resistant and puncture-resistant soles. Safety-toed footwear is worn to prevent crushed toes when working around heavy equipment or falling objects.
  • Hand Protection. Gloves should fit snugly. Workers should wear the right gloves for the job (examples: heavy-duty rubber gloves for concrete work; welding gloves for welding; insulated gloves and sleeves when exposed to electrical hazards).
  • Head Protection. Wear hard hats where there is a potential for objects falling from above, bumps to the head from fixed objects, or of accidental head contact with electrical hazards. Hard hats - routinely inspect them for dents, cracks or deterioration; replace after a heavy blow or electrical shock; maintain in good condition.
  • Hearing Protection. Use earplugs/earmuffs in high noise work areas where chainsaws or heavy equipment are used; clean or replace earplugs regularly.

It's important to remember that, like administrative controls, the use of PPE does not control the hazard itself, but rather it merely controls exposure to the hazard by setting up a barrier between the employee and the hazard. Use of PPE may also be appropriate for controlling hazards while engineering controls are being installed or work practices developed.

We'll cover PPE in more detail in the next module.

For more information on PPE, take OSHAcademy Course 700, Personal Protective Equipment, and see OSHA's Publication 3151, Personal Protective Equipment.

Hazard Controls

Viewing this video is optional.


Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.

Good luck!

1. Removing the source of excessive temperatures, noise or pressure is an example of _____.

2. Redesigning a piece of equipment so that it is not so noisy when operating is an example of _____.

3. Changing the work schedule so that workers have reduced exposure to noisy equipment is an example of _____.

4. Using ear plugs when working around noisy equipment is an example of which control strategy?

5. If a hazard exists, what action should be taken immediately?

Have a great day!

Important! You will receive an "error" message unless all questions are answered.