COVID Straight Talk—M.A.D. Guidelines and the “Hierarchy of Controls”
A Deep Dive Into Workplace Safety for Employers
This is a quick reference for employers that shows how our M.A.D. (Masks, Air, and Distance) Guidelines correlate to the Centers for Disease Control and Prevention (CDC) and the National Institutes of Occupational Safety and Health (NIOSH) “Hierarchy of Controls.” Employers can use these guidelines to address workplace safety measures with workers, management, and HVAC professionals, as well as to understand the level at which safety measures are best addressed and implemented.
The CDC and NIOSH created the Hierarchy of Controls to address workplace safety.
Employers can use this framework strategically to create safe workplaces.
Some important points employers should keep in mind behind the Hierarchy of Controls:
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Safety measures at the top of this pyramid may have higher initial costs, but are potentially more effective at eliminating and/or reducing risks to employees and others—which can be more cost-effective in the long term
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Safety measures at the bottom of the pyramid may have lower initial costs, but do not completely eliminate COVID-19 from the workplace. These measures rely on individuals’ compliance with regulations and can be costly to sustain in the long term
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At this time, it is beyond both employer and employee controls to completely eliminate the risk of COVID-19. Until there is a vaccine or effective treatments available, the virus is here
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The pyramid, below, illustrates how employers can identify and most effectively implement safety measures that will have the most impact on workplace safety
Breaking Down the Hierarchy
Elimination controls are not currently available for COVID-19. Until there is a vaccination that prevents people from getting the virus, it’s impossible to entirely remove the risk.
Substitution controls are also not currently available. In the absence of proven treatments that lessen the severity of symptoms and death from COVID-19, there is no “substitution” that will mitigate the risk.
Engineering controls isolate or separate workers from the virus through mechanical or structural means and are available to employers to help them mitigate the risk of COVID-19. Taking steps to prevent the virus from entering the workplace, such as updating and maintaining the HVAC filtration system, increasing the air refresh rate, and monitoring the humidity in the workplace will greatly reduce the risk of COVID-19.
Administrative controls require implementing policies and procedures that change the way people behave in the workplace to minimize their risk. Employers should implement changes in policies such as staggering shifts, redesigning work areas, and allowing employees to work from home in order to prevent the spread of COVID-19.
PPE controls rely on changing the behaviors of employees and others in the workplace, such as mandating and providing masks and encouraging good personal hygiene. Employers must mandate the use of and provide employees with proper PPE in order to prevent person-to-person spread of the virus.
The prevalent use of lower-level (ie, PPE and Administrative) controls in responding to COVID-19 highlights the importance of using this framework.
Administrative and PPE controls are less effective at eliminating the risk of COVID-19 because they rely on compliance. However, because these protections can be more readily available and have lower initial costs, they can be important safety bridges while more effective solutions are put in place. It’s critical to reassess every possible option in the hierarchy throughout this pandemic.
Given the evidence that COVID-19 may be airborne (transmitted by small particles in the air, not just droplets), employers must put safety measures in place that will protect workers from this type of exposure.
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It is not enough for employers to rely on workers to wear PPE to protect themselves and others from COVID-19, even if it’s mandated. Employers must take a multimodal approach to effectively mitigate risk
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Managers and corporate decision makers are responsible not only for providing and mandating the use of PPE, but also for implementing both Administrative and Engineering controls to make the workplace environment itself safe. Read our Legal Guide for Workers that we created with the National Employment Law Project (NELP) here:
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Employers, building administrators, and managers have greater control over Engineering changes such as updating and maintaining HVAC systems that reduce the likelihood of the virus entering the workplace, as well as Administrative changes such as instituting policies and procedures that reduce risks
Our M.A.D. Guidelines correlate to 3 levels of the NIOSH Hierarchy of Controls (PPE, Engineering, and Administrative, respectively), as well as to who has the decision-making power to effect those changes. By understanding the hierarchy levels at which M.A.D. Safety Measures are implemented, employers can better protect employees from the risk of COVID-19.
The next section outlines specific safety measures that lessen the risk of COVID-19 and the level of control responsible for ensuring those measures are taken.
Masks = PPE Controls
PPE controls are often the easiest and cheapest safety measures to put in place. But because even mandated PPE regulations depend on individuals’ compliance and does not prevent the virus from entering the workspace, PPE controls are less effective at lowering the risk of COVID-19.
Safety Measures
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However, PPE is vital for everyone’s safety—masks are still the best protection against person-to-person transmission of COVID-19. If all employees wear masks properly while at work (inside and outside), their risk of getting the virus is significantly reduced.
Air = Engineering Controls
Engineering controls are considered the most effective way to reduce the risk of COVID-19 in the workplace because it does not rely on compliance, but isolates workers and others from exposure to the virus by preventing it from entering the indoor environment. Employers should consider the long-term benefits of implementing these safety measures to protect workers.
Safety Measures
HVAC systems are complicated, but a basic understanding of how these systems interact with air is vital to understanding how to stop the virus from spreading. COVID-19 may hang in the air for a long time, which means that when indoor air is circulated through the HVAC system, the virus may go with it. Even if a person who has COVID-19 (asymptomatic or symptomatic) is in a different room or has left the building, the virus particles can still reach others through the HVAC system.
There are four factors that impact the spread of the virus through HVAC systems: air velocity, air refresh rate, humidity, and filtration.
Air velocity refers to how fast the air in the space is moving. Increasing air velocity will move virus particles from the air down onto surfaces, which can be more easily disinfected. Surfaces should be cleaned and disinfected frequently (at least once a day) in the workplace to prevent contact transmission. Workers need to wear masks correctly, and wash their hands with soap and water for at least 20 seconds after touching surfaces. Increasing air velocity also breaks down “vapor clouds” of droplet particles that can form in stagnant indoor air.
Air refresh rate, or exchange rate, is how frequently HVAC systems draw in fresh air from outside into the indoor space. As long as your workplace is in an area with clean outdoor air (ie, no fumes, smoke from fires, or other contaminants), outside air will help reduce the density of virus particles in the air, lowering the risk of infection. This is often called “100% Outside Air” or “High Refresh” mode on HVAC controls.
Humidity is how much water vapor is in the air. Virus particles float in the air longer in very low humidity. In addition, low humidity levels can dry out your nose and eyes and damage the immune system. Therefore, ventilation experts recommend maintaining relative humidity (which changes depending on factors such as air pressure and temperature) between 40%–60%.
Filtration traps particles and prevents contaminants from being circulated in the air. High-efficiency filters can trap most COVID-19 virus particles (~99%), so offer good protection. However, knowing which filter to use is important. The age and type of HVAC system buildings use varies. The highest-efficiency filter is not always the best choice because not all HVAC systems perform well using these filters. High-efficiency particle absorbing (HEPA) filters are known to be the highest-efficiency filter available, and are often used in hospital buildings. However, putting a HEPA filter into an incompatible HVAC system can cause a sudden pressure drop that damages the system itself. There is no one right answer, but experts recommend using the highest-efficiency filter that is compatible with the system in use. Work with an HVAC professional to make the best decision.
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HEPA filters: These filters will trap nearly all COVID-19 virus particles in the ventilation system and prevent them from entering the space. HEPA filters are more than 99% effective at removing ultrafine droplets (0.01 microns)
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MERV (minimum efficiency reporting value) 13+ filters: MERV is a measure of how effective a filter is at removing a specific size of particle. MERV 8+ filters have some ability to trap virus particles, but MERV 13+ filters are known to remove the majority of virus particles
Distance = Administrative Controls
Administrative controls are effective in reducing risk by establishing policies and procedures that make it easy for individuals to follow proper safety precautions. Staggering and rotating work shifts, and redesigning workspaces to increase physical distancing among coworkers and others (such as moving workstations, using plexiglass barriers, and creating outdoor work areas) will lower the risk of COVID-19 in the workplace.
Safety Measures
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Time How long each person spends in an indoor space with other people.
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Density Density is the number of people in the indoor space at a given time—the fewer people in the workplace at one time, the lower the Density.
Minimizing the length of time employees spend working indoors as well as the length of workshifts and breaks will reduce the risk of COVID-19 in the workplace. Risks associated with density can be reduced by minimizing the number of people working close to each other, spreading out workstations across the space, and staggering work shifts. Rotating working from home with working onsite and staggering shifts throughout the day will reduce risks associated with both time and density.
