Hierarchy of Controls

Strategies for mitigating risk can be assessed using the Hierarchy of Controls framework.   It organizes mitigation strategies, or controls, in order of effectiveness. Under this framework, one should first consider the feasibility of the more-effective controls (e.g., substitution) before considering less-effective measures (e.g., administrative controls).  As demonstrated in the graphic below, PPE is the last line of defense in the hierarchy of controls.

From the National Institutes for Occupational Safety and Health.

The hierarchy of controls prioritizes intervention strategies based on the premise that the best way to control a hazard is to systematically remove it from the workplace, rather than relying on workers to reduce their exposure. The types of measures that may be used to protect laboratory workers, prioritized from the most effective to least effective, are: 

• engineering controls; 

• administrative controls;

 • work practices; 

• personal protective equipment (PPE). 

Most employers use a combination of control methods. Employers must evaluate their particular workplace to develop a plan for protecting their workers that may combine both immediate actions as well as longer term solutions. A description of each type of control for non-production laboratories follows.

Engineering controls are those that involve making changes to the work environment to reduce work-related hazards. These types of controls are preferred over all others because they make permanent changes that reduce exposure to hazards and do not rely on worker behavior. By reducing a hazard in the workplace, engineering controls can be the most cost-effective solutions for employers to implement. 

Examples include: 

• Chemical Fume Hoods; 

• Biological Safety Cabinets (BSCs).

Administrative controls are those that modify workers’ work schedules and tasks in ways that minimize their exposure to workplace hazards. 

Examples include: 

• Developing a Chemical Hygiene Plan; 

• Developing Standard Operating Procedures

Work practices are procedures for safe and proper work that are used to reduce the duration, frequency or intensity of exposure to a hazard.  When defining safe work practice controls, it is a good idea for the employer to ask workers for their suggestions, since they have firsthand experience with the tasks as actually performed. These controls need to be understood and followed by managers, supervisors and workers. 

Examples include: 

• No mouth pipetting; 

• Chemical substitution where feasible (e.g., selecting a less hazardous chemical for a specific procedure).

Personal Protective Equipment (PPE) is protective gear needed to keep workers safe while performing their jobs. Examples of PPE include respirators (for example, N95), face shields, goggles and disposable gloves. While engineering and administrative controls and proper work practices are considered to be more effective in minimizing exposure to many workplace hazards, the use of PPE is also very important in laboratory settings. 

It is important that PPE be: 

• Selected based upon the hazard to the worker; 

• Properly fitted and in some cases periodically refitted (e.g., respirators);

 • Conscientiously and properly worn; 

• Regularly maintained and replaced in accord with the manufacturer’s specifications; 

• Properly removed and disposed of to avoid contamination of self, others or the environment; and

 • If reusable, properly removed, cleaned, disinfected and stored.