Chemical Hierarchy of Controls (HOC) Strategies
Hazardous substances can be used safely in workplaces if adequate control strategies are used to prevent exposure to those chemicals.
A control strategy includes any device, procedure, piece of equipment, system, etc., that is used to keep hazardous chemicals from contacting workers at harmful levels. Traditionally, a prioritized "Hierarchy of Controls" (HOC) has been used to implement feasible and effective exposure controls to protect workers. We encourage the use of the HOC model as described within the ANSI/ASSP Z10, Occupational Health and Safety Management Systems, to control hazards. The six strategies are discussed below.
The first three HOC strategies focus on addressing the hazard directly to eliminate or reduce exposure and risk.
- Elimination: This is the best solution because it completely eliminates the use of hazardous substances and chemicals.
- Substitution: Substitution is the next-best solution. The strategy is to replace a toxic substance with a less-toxic substance. If you can't remove the toxic substances, you may be able to replace them with substances that are less toxic. For more information on safer alternative chemicals to use in the workplace, see the ChemHAT Chemical Hazard and Alternatives Toolbox.
- Engineering Controls: This strategy relies on the design or redesign of tools, equipment, machinery, or processes that use toxic chemicals to eliminate or reduce exposure to the chemical hazard itself.
The next three HOC strategies aim to modify behaviors to reduce exposure to the hazard.
- Warnings: This strategy includes the use of signs, labels, alarms, and signals to warn employees about the presence of hazards. While not eliminating or reducing the hazard itself, warnings help by raising awareness and guiding behavior.
- Work Practice Controls: These controls (also known as administrative controls) involve changing work procedures and practices to reduce the duration, frequency, and severity of exposure to the chemical hazard. The controls do not eliminate or reduce the chemical hazard itself. Instead, they focus on mandating safer procedures and practices to protect employees. A major drawback is that these controls only protect workers if they comply with the control measures. If employees do not comply with the procedures and practices, the control measures are ineffective.
- Personal Protective Equipment (PPE): The use of PPE is the most common strategy and is mandatory when working with hazardous chemicals. PPE forms a barrier between the worker and the hazard. Once again, the chemical hazard is neither eliminated nor reduced, and a high reliance is placed on appropriate use of PPE for this strategy to be successful.
Remember, the first question to ask is, 'How can I eliminate, reduce, or engineer out the hazard?' Hopefully, you'll be able to eliminate the hazard or reduce it to an acceptable level where safe behaviors or PPE won't be necessary.
Interim Measures
Using a lower priority hazard control method over another higher priority control strategy may be appropriate for providing interim (temporary) protection until the hazard is abated permanently. If you can't eliminate the hazard entirely, the interim control measures will likely be a combination of control methods used together. OSHA believes that feasible interim measures are always available if higher-level control methods are not possible.
See examples of each of these the HOC strategies and interim measures below:
- Elimination:
- Removing a hazardous machine from the workplace.
- Discontinuing a dangerous work process.
- Substitution:
- Replacing a toxic cleaning chemical with a non-toxic alternative.
- Using lead-free paint instead of lead-based paint.
- Engineering Controls:
- Installing ventilation systems to remove airborne contaminants.
- Using soundproof materials to reduce noise levels.
- Warnings:
- Posting signs near high-voltage equipment.
- Applying color-coded labels to chemical storage containers.
- Administrative/Work Practice Controls:
- Rotating employees to reduce exposure to repetitive stress injuries.
- Implementing mandatory rest breaks to decrease fatigue.
- Personal Protective Equipment (PPE):
- Providing respirators in environments with airborne pollutants.
- Requiring steel-toed boots on construction sites.
- Interim Measures:
- Using temporary guardrails during the construction of a permanent fixture.
- Employing portable ventilation units while a fixed system is being installed.
Knowledge Check Choose the best answer for the question.
2-6. What HOC strategy would be the first to consider when trying to reduce exposure to hazardous chemicals?
You forgot to answer the question!