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Course 833 - Developing a Construction Safety Management System

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

Controlling Worksite Hazards

Accident weed
The Hierarchy of Controls: Reduce hazards and exposure.

The Hierarchy of Controls (HOC)

As you learned earlier, there are many different types of hazards in the workplace.

  • Hazardous conditions include unsafe materials, equipment, 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, called the "Hierarchy of Controls" have been developed.

ANSI/ASSP Z10-2012, Occupational Health and Safety Management Systems, encourages employers to use the following hierarchy of hazard controls:

Hazard Controls

  1. Elimination
  2. Substitution
  3. Engineering controls

Exposure Controls

  1. Warnings
  2. Administrative controls
  3. Personal protective equipment

Check out this short audio clip by Dan Clark of talks about the Hierarchy of Controls.

The idea behind this hierarchy is that the control methods at the top of the list are potentially more effective and protective than those at the bottom. Following the hierarchy normally leads to the implementation of inherently safer systems, ones where the risk of illness or injury has been substantially reduced. We'll take a closer look at the hierarchy of control strategies. First, let's learn about "feasible."

"Feasible" Controls

No money
The Hierarchy of Controls: Reduce hazards and exposure.

Hazard abatement measures required to correct a hazard must be technologically and economically feasible for the employer. OSHA uses the following criteria to determine feasibility of engineering and administrative 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 to cited violations with a reasonable possibility that employee exposure to occupational health 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 such time as 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 and Substitution

Eliminate the Hazard - NAPO

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.

These strategies are considered first because they have the potential to completely eliminate the hazard, thus greatly reducing the probability of an accident due to the hazard.

Some examples of these two strategies include:

  • Removing the source of excessive temperatures, noise, or pressure - this is "elimination."
  • Substituting a toxic chemical with a less toxic or non-toxic chemical - this is "substitution."

Engineering Controls

Hierarchy of Controls
Engineering Controls: Control through design.

These controls focus on eliminating or reducing the actual source of the hazard through design or redesign. Other control strategies that generally focus on employee exposure to the hazard. The basic concept behind engineering controls is that, to the extent feasible, the work environment and the job itself should be designed to eliminate hazards 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. Redesigning or replacing equipment or machinery may be expensive, but remember, the cost per medically consulted injury can be more than $42,000, and the cost per death $1,500,000 or more.

Remember: No hazard or No exposure = No accident.

Engineering controls do not necessarily have to be expensive or complicated. They can be quite simple in some cases. Engineering controls are based on the following broad strategies:

  1. If feasible, design or redesign the tools, equipment, machinery, materials and/or facility.
  2. Enclose the hazard to prevent exposure in normal operations; and
  3. If complete enclosure is not feasible, establish barriers or local ventilation to reduce exposure to the hazard in normal operations.

Some examples of this strategy include:

  • Redesigning a process to reduce exposure to a hazardous moving part;
  • Redesigning a work station to relieve physical stress and remove ergonomic hazards; or
  • Designing general ventilation with sufficient fresh outdoor air to improve indoor air quality and generally to provide a safe, healthful atmosphere.

Engineering Controls (Continued)

Enclosure of Hazards

engineering controls
Enclosure of a rotating shaft hazard.

When you cannot remove a hazard and cannot 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 operations. There still will 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;
  • 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; and
  • Complete containment of noise, heat, or pressure producing processes with materials especially designed for those purposes.

Barriers or Local Ventilation

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

Barriers and local ventilation involve potential exposure to the worker even in normal operations. Consequently, they 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 laboratory work
  • machine guarding, including electronic barriers
  • isolation of a process in an area away from workers
  • baffles used as noise-absorbing barriers
  • nuclear radiation or heat shields


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

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.

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

How do you control unsafe behaviors?

Administrative controls are aimed at reducing employee exposure to hazards that engineering controls fail to eliminate. Administrative controls work by designing safe work practices into job procedures and adjusting work schedules. Ultimately, effective administrative controls will successfully eliminate the human behaviors that result in 95% of all workplace accidents!

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 management controls that tend to work only as long as employees behave. Here's an important principle that reflects this idea:

Any system that relies on human behavior is inherently unreliable.

To make sure management controls are effective in the long term, they must be designed from a base of solid hazard analysis and sustained by a supportive safety culture. They then must be accompanied by adequate resources, training, supervision, and appropriate consequences. Remember, administrative controls should be used in conjunction with, and not as a substitute for, more effective or reliable engineering controls. Now let's look at some examples of some administrative controls.

Safe Work Practices

unsafe behavior
Can you see the missing PPE?

Safe work practices may be quite specific or general in their applicability. They may be a very important part of a single job procedure or applicable to many jobs in the workplace.

General safe work practices: These are common to most workplace and include:

  • removing tripping, blocking, and slipping hazards
  • using safe lifting techniques
  • maintaining equipment and tools in good repair
  • using personal protective equipment (PPE)

Specific safe work practices: Other safe work practices apply to specific jobs in the workplace and involve specific procedures for accomplishing a job. Examples of specific safe work procedures include:

  • wetting down surfaces to keep toxic dust out of the air
  • testing the air quality within a confined space
  • placing chocks when parking a truck
  • placing forks on the ground when the forklift is parked

To develop safe procedures, you conduct a job hazard analysis (JHA). If, during the JHA, you determine that a procedure presents hazards to the worker, you would decide that a training program is needed. We recommend using the JHA as a tool for training your workers in the new procedures. A training program may be essential if your employees are working with highly toxic substances or in dangerous situations.

Personal Protective Equipment (PPE)

Wearing PPE is always a best practice.

Using personal protective equipment is a very important safe work practice. It's important to remember that, like other 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.

PPE Drawbacks

The limitations and drawbacks of safe work practices also apply to PPE. Employees need instruction in why the PPE is necessary and hands-on training on how to use and maintain it. It's also important to understand that PPE is designed for specific functions and are not suitable in all situations. For example, no one type of glove or apron will protect against all solvents. To pick the appropriate glove or apron, you should refer to recommendations on the safety data sheets (SDSs) of the chemicals you are using.

Your employees need positive reinforcement and fair, consistent enforcement of the rules governing PPE use. Some employees may resist wearing PPE according to the rules, because some PPE is uncomfortable and puts additional stress on employees, making it unpleasant or difficult for them to work safely. This is a significant drawback, particularly where heat stress is already a factor in the work environment. An ill-fitting or improperly selected respirator is particularly hazardous, since respirators are used only where other feasible controls have failed to eliminate a hazard.

Interim Measures

There's always a possible interim measure.

When a hazard is recognized, the preferred correction or control cannot always be accomplished immediately. However, in virtually all situations, interim measures can be taken to eliminate or reduce worker risk. 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. By the way, OSHA believes there is always some kind of interim measure that can be used to temporarily abate a hazard.

Maintenance Strategies

Preventive maintenance is proactive!

There are two general types of maintenance processes needed to control hazards:

  • Preventive maintenance to make sure equipment and machinery operates safely and smoothly.
  • Corrective maintenance to make sure equipment and machinery gets back into safe operation quickly.

Hazard Tracking Procedures

An essential part of any day-to-day safety and health effort is the correction of hazards that occur in spite of your overall prevention and control program. Documenting these corrections is equally important, particularly for larger sites.

Documentation is important because:

  • It keeps management and safety staff aware of the status of long-term correction items;
  • It provides a record of what occurred, should the hazard reappear at a later date; and
  • It provides timely and accurate information that can be supplied to an employee who reported the hazard.

The hierarchy of controls is the standard system of strategies to effectively eliminate workplace hazards. Remember, the first question to ask when considering ways to eliminate a hazard is, "can we apply engineering controls?" You may need to use a combination of strategies to effectively eliminate the hazard. Whatever it takes, do it. You are not just saving a are saving a father, a mother, a son, or a are saving a family. It's worth the effort!




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. What may be a contributing factor in up to 95 percent of all workplace accidents?

2. Which cause category is ultimately responsible for most accidents in the workplace?

3. Which of the following is not one of the five areas within which all workplace hazards exist?

4. Which method of controls is most effective at reducing hazards?

5. Which method of controls has also proven to be less effective than other measures, requiring significant effort by the affected workers?

Have a safe day!

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