Protecting Essential Workers

SARS-CoV-2, the virus that causes COVID-19, spreads from person to person when they breathe in (or inhale) infectious aerosols, or tiny particles that can remain suspended in the air for long periods. These particles spread easily throughout an indoor space, so physical distancing does not guarantee protection. Contact transmission (transfer of the virus by hands to nose, mouth, or eyes) may also be possible, but the CDC deems that to be less important than close direct contact with respiratory particles. We do not know how many SARS-CoV-2 virus particles are required for infection, but it is likely to be few. Infection is believed to occur when the following conditions are met, according to the CDC: being within 6 feet of an infectious person for a cumulative (total) time of 15 minutes over a 24-hour period. 

For transmission to occur via tiny airborne particles, three things are necessary:


First, there must be a sourcea person with COVID-19 creates small respiratory particles containing SARS-CoV-2 viruses when they breathe, talk, cough, sneeze, yell, or sing. This could be a worker or customer who may not know they have COVID-19. At least 20% of infected people do not have symptoms, and many others have mild symptoms (Beale et al., 2020, Byambasuren et al., 2020, Buitrago-Garcia et al., 2020, He et al., 2020). Respiratory aerosols will be infectious  2 to 3 days before symptoms and up to 8 to 10 days after symptoms develop (Cevik et al., 2020a, 2020b, Lauer et al., 2020, McAloon et al., 2020). Anyone can be a sourcea worker, co-worker, or member of the public.

Second, there must be a pathway or route from a person with COVID-19 (the source) to an uninfected person (the receptor). In the case of aerosols, this pathway will be through the air. The tiny infectious particles must remain suspended in and distributed throughout an indoor space, where they can be inhaled by someone else. 

Third, a person without COVID-19 (the receptor) must breathe in enough virus-containing particles to be infected. Because infectious dose (the amount of viruses inhaled) depends on the concentration of airborne virus and how long the exposure is, a person can be infected by inhaling a lot of virus in a short time (minutes) or fewer infectious particles over a longer time (hours). Once infected, a person’s characteristics, such as age and other health conditions (eg, pregnancy, diabetes, heart disease), determine whether symptoms are mild or severe (CDC, 2021).

Overall, the best interventions for preventing the spread of SARS-CoV-2 in a workplace are those that eliminate or minimize the source followed by those that interrupt the path from source to receptor. The third category of intervention, focused on uninfected people (receptors), should only be undertaken when all source and pathway interventions have been put in place.  

Our economy and society rely on workers that face great risks because their jobs may require them to be in close or prolonged contact with co-workers or members of the public. These essential workers may perform jobs in healthcare, food processing, warehousing, retail, transportation, security, etc. Essential workers need the best possible protection from infectious respiratory aerosols in their jobs to prevent COVID-19.

The following sections focus on the actions or interventions employers may take to protect workers in the workplace. Source and pathway interventions are more effective and should be implemented first. Vaccinations for COVID-19 are the first level of protection for essential workers, and their importance cannot be minimized. However, the vaccines are not perfect, and the following strategies are critical for keeping essential workers safe. 

Strategy 1: Eliminate or minimize the sources


Worker-to-Worker Interventions

Client/Customer-to-Worker Interventions

Impact of Intervention

Identify and exclude sources

Work remotely

Conduct nasal, throat, or saliva testing every 2-3 days and provide paid leave for workers who test positive

Offer no-contact pickup and delivery

Eliminates or greatly reduces exposure and transmission

Reduce the number of sources

Change workflow or scheduling to limit employee interactions

Limit the number of workers in the same space at any given time

Limit number of customers served, such as switching to appointment-only service

Limit the size of groups allowed for services, such as limiting the number of visitors at a hospital

Lowers exposure my minimizing concentration over time

Minimize duration or type of contact with sources

Use headsets or handheld radios to reduce length of interactions

Order pick-up or take-out

Reduces exposure by reducing concentration or time

Decrease aerosols (tiny airborne particles)


Wear cloth face coverings

Minimizes exposure by minimizing concentration

Cloth face coverings (face masks) worn by the public may protect workers from larger virus particles and should be required for anyone from the public in a workplace. Interactions between members of the public and workers should be limited.

Cloth face coverings worn by workers will not protect co-workers whose exposure extends over hours. Cloth face coverings do not prevent the outward leakage of all particles. With enough time, an infectious person wearing a cloth face covering will emit enough particles that the concentration in the space will increase to a dangerous level.

Strategy 2: Interrupt the pathway


Worker-to-Worker Interventions

Customer/Client-to-Worker Interventions

Impact of Intervention

Increase airflow

Increase the number of air changes per hour

Increase the number of air changes per hour

Lowers exposure by lowering concentration and time

Remove the air from or clean the air at the source

Install portable air cleaners at each work station

Install portable air cleaners near every point of interaction

Lowers exposure by lowering concentration

Partitions, barriers, and splash guards may limit how many large infectious droplets travel from a source to a receptor, but they will not be effective at containing or preventing the spread of smaller infectious particles throughout a space.

Strategy 3: Protect the receptor

(Many of these interventions will protect the public as well)



Impact of Intervention

Isolate the receptor from potential sources

Have a separate workspace or office for each worker

Eliminates or lowers exposure and transmission

Clean the air before people breathe it in

Provide workers with fit-tested respirators (such as N-95s, often worn by healthcare workers) and a respiratory protection program, as per OSHA

Eliminates or lowers exposure by lowering concentration

Personal protective equipment (PPE), and in particular respiratory protection, must be preserved for front-line healthcare  and other workers whose jobs bring them into direct contact with people with suspected or confirmed COVID-19. When supplies are limited, respirators should be preserved for frontline healthcare workers, police, and other essential workers whose jobs ensure public health and security. 

Cloth face coverings and masks do not provide adequate protection for workers, especially those whose jobs involve contact with many people or lengthy contacts with co-workers or the public. If source and pathway controls do not adequately eliminate or minimize exposure to infectious aerosols, workers require fit-tested respirators and an OSHA-compliant respiratory protection program. See: 

For help with workplace health and safety, industrial hygienists and occupational health and safety professionals can provide guidance and resources. Such professionals can be found by contacting the American Industrial Hygiene Association (, ACGIH (, American College of Occupational and Environmental Medicine ( or American Association of Occupational Health Nurses (

Additional resources: 


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