COVID-19 Prevention: Following the Hierarchy of Controls

Minimizing exposure to the novel coronavirus is key to protecting UArizona students, faculty and staff from COVID-19. We accomplish this by following the hierarchy of controls, the framework used in occupational health for selecting the most effective control solutions for exposures that may cause disease. The hierarchy of controls was developed by the National Institute for Occupational Safety and Health (NIOSH) and is so integral to occupational health that it is frequently referenced by the Occupational Safety and Health Administration (OSHA) in regulations and guidance. 

This illustration is based on the hierarchy of controls developed by the National Institute for Occupational Safety and Health (NIOSH). It is also available as a PDF document or text-only.

Elimination of exposure is accomplished primarily through physical distancing. Examples:

  • Ensuring individuals do not come to campus when they are ill.
  • Eliminating unnecessary trips out of the home.
  • Working and learning from home.

Engineering controls attempt to separate individuals from the potential source of exposure. Examples:

  • Sufficient ventilation to remove infectious droplets from the air.
  • Use of barriers between people, including installing a plastic shield at a customer service desk or moving from a cubicle space into an office with a door.
  • Move desk(s) into conference rooms to spread people out.

Administrative controls change the way we interact with one another and our environment. Examples:

  • Put policies in place that encourage physical distancing, remote working and learning, staggered work schedules, staggered arrival and departure times to prevent congregating in elevators and common areas.
  • Reduce occupancy to encourage physical distancing (for example, only 50% of workers present at a time).
  • Alternate work from home and office days to reduce occupancy. Consider moving to shifts (for example, 6 a.m. to 12 p.m., and 1 p.m. to 7 p.m. with an hour to clean in between), allowing you to cut occupant density in half.
  • Decide which workers need to be onsite, and create work teams that can be isolated from one another physically or over time (alternating shifts or days of the week, for example). Should a member of a team get sick, this allows them to self-quarantine and shut down work teams, without affecting other teams.
  • Allow at least 6 feet between individuals and always encourage low-occupancy density of shared spaces.
  • Put policies in place that encourage handwashing, disinfection of potentially contaminated surfaces.

Personal Protective Equipment (PPE) involves the use of respirators, gloves and protective clothing:

  • While PPE may initially be less expensive than other control methods, one challenges is that supplies must be readily available and distributed throughout our community.
  • PPE effectiveness is dependent on consistent, careful use and care of the equipment.
  • PPE users must be trained on the proper wear and removal of PPE to avoid accidental contamination of their body or other surfaces. Touching your face, cell phone, or steering wheel with contaminated gloves, for example, can lead to exposure.

Face Coverings reduce droplet transmission from infected individuals, protecting others.

  • To maximize the benefit of face coverings, they MUST be used in combination with other controls – physical distancing and limiting in-person contact with others, surface decontamination, hand hygiene – following the hierarchy of controls (Figure 1).
  • Wearers must practice hand hygiene – every time you put on, take off or touch your face covering, wash your hands! Wear a clean face covering each time you put one on.
  • UArizona community members are required to wear face coverings, per the University’s Administrative Directive.

Frequency, Intensity & Duration

The controls presented in the hierarchy are complimentary and when used together, provide successive layers of protection. None of the controls are perfect, as they all involve humans and there is variability in all we do. Risk minimization and exposure prevention rely on controlling the frequency, intensity and duration of exposure.

We want to keep people working/learning remotely, alternating work schedules and using Zoom for meetings because those kinds of controls minimize the frequency of contact between infectious and susceptible people. We can shorten the amount of time in a given day that people spend in the office by encouraging them to work from home; we can create hybrid classes; and, keep all in-person interactions intentionally brief to minimize the duration of exposure. We make statements like, “if you’re sick stay home!” We encourage the use of physical distancing in all settings, and finally, mandate the use of face coverings, to minimize the intensity of exposures.

The aerosol and virus science does not support the reliance on physical distancing alone. You will often hear advice to maintain “6 foot distancing” or some recommended square foot per person, which encourages low-density occupancy in shared spaces. The challenge is that when exposure occurs over time, the risks are not the same as when the exposure is brief (one helpful read on this is can be found here) Being in close proximity to an infectious person who is simply breathing, or even talking quietly, is relatively low risk if that exposure does not continue for enough time. This is because susceptible individuals need to receive an “infectious dose” for the virus to effectively spread.  The CDC currently defines “close contact” as being within 6 feet of a symptomatic or COVID-positive person for 15 or more minutes.

All the controls work well together and are much less effective when used alone, especially face coverings. Other than complete isolation (which is likely infeasible for most people for the duration of the pandemic), no control alone adequately addresses all of the factors of frequency, intensity and duration.

Protect Yourself and Your Community

Before returning to UArizona campus or facilities, individuals and their supervisors should ask themselves the following questions:

  1. How can I eliminate the risk of exposure?
  • Stay home if you are sick. Text > Report > Protect via Wildcat Wellcheck.
  • Take only essential trips from the home.
  • Work / Learn from home. Use Zoom and other technology to stay connected.
  1. How can I change the way I work or learn to reduce risk of exposure?
  • Implement/follow policies that encourage physical distancing (remote working and learning, staggered work schedules, etc.).
  • Reduce occupancy to encourage physical distancing (for example, only 50% of workers present at a time, minimum of 6 feet between individuals, low density occupancy of shared spaces).
  • Encourage individuals to reduce unnecessary trips out of the home, practice hand hygiene and disinfect surfaces.
  1. How can I use Face Coverings, along with other controls, to reduce the risk of exposure in our community?
  • Continue to practice physical distancing, limit in-person contact with others and decontaminate surfaces.
  • Practice and encourage hand hygiene.
  • Remember Face Coverings are not PPE. You may get sick even if you wear one, especially if you fail to follow the hierarchy of controls.
  • Wear face coverings, per the University’s Administrative Directive.

Classroom

Elimination of exposure is accomplished primarily through physical distancing. Examples:

  • Ensuring individuals do not come to campus when they are ill.
  • Reduce occupancy to encourage physical distancing (for example, only 50% of students present at a time).
  • Learning from home (hybrid classes, online options).

Engineering controls attempt to separate individuals from the potential source of exposure. Examples:

  • Improved air filtration in HVAC systems.
  • Increased fresh air mix in building ventilation wherever feasible.

Administrative controls change the way we interact with one another and our environment. Examples:

  • Frequent classroom cleaning (5 days/week).
  • EPA-approved disinfectant and hand sanitizer in classrooms.

Personal Protective Equipment (PPE) involves the use of respirators, gloves and protective clothing:

  • While PPE may initially be less expensive than other control methods, one challenges is that supplies must be readily available and distributed throughout our community.
  • PPE effectiveness is dependent on consistent, careful use and care of the equipment.
  • PPE users must be trained on the proper wear and removal of PPE to avoid accidental contamination of their body or other surfaces. Touching your face, cell phone, or steering wheel with contaminated gloves, for example, can lead to exposure.

Face Coverings reduce droplet transmission from infected individuals, protecting others.

  • To maximize the benefit of face coverings, they MUST be used in combination with other controls – physical distancing and limiting in-person contact with others, surface decontamination, hand hygiene – following the hierarchy of controls (Figure 1).
  • Wearers must practice hand hygiene – every time you put on, take off or touch your face covering, wash your hands! Wear a clean face covering each time you put one on.
  • UArizona community members are required to wear face coverings, per the University’s Administrative Directive.