Air cleaners for your workplace: simple solutions = big misconceptions.

In the workplace, everyone has a responsibility to protect not only their health but the health of their co-workers, customers, and visitors. This is particularly true in the case of a pandemic emergency caused by the COVID-19 outbreak. Information, training, vocational preparation, and appropriate protective equipment should all be provided to enable everyone to work safely.

This article will discuss some protective measures currently used in the workplace. However, it will not address the principles of personal and industrial hygiene in the case of a SARS-CoV-2 virus outbreak. Such principles are the same as for other biological hazards and do not guarantee complete elimination or isolation of the hazard’s source. This is because any person in or visiting the workplace can be a carrier of an airborne infection.

The article will consider the current internal measures available to employers, business owners, buildings, and managers of institutions. These include:

  1. Existing, forced (mechanically induced) ventilation of premises
  2. Protective screens to ensure safe contact of employees and customers
  1.  Indoor ventilation, central air conditioning, and air heating

Today, in the context of the coronavirus pandemic, the use of centralized (supply and exhaust) ventilation causes controversy among specialists. Some countries and regions even prohibit the use of ventilation systems to prevent the spread of viral infection.

Opponents of such measures rely on the confirmed fact that any SARS virus can be, and typically is, transmitted by airborne droplets. Since SARS-CoV-2 is related to the SARS 2002 virus, and considering data from previous studies, it is accepted that aerosolization is a potential method of transmission. “Aerosolization” is when a substance is converted into particles that are small and light enough to be carried on the air. Rooms with heating, ventilation, and air conditioning devices may therefore enable the spread of the virus.

Experiments show that a new coronavirus SARS-CoV-2 can remain viable in the air for three hours, as discussed in this article

Studies have also shown that ventilation, heating, and air conditioning systems increase the risk of transmission. Such systems can contribute to virus transmission by recirculating polluted air and/or creating internal conditions (temperature and humidity) that support virus survival.

As detailed in this article, virus droplets can be transmitted beyond the so-called “safe” two-meter distance, and infection can occur within mere minutes.

Dr. Lee Ju-hyung, a professor at the Jeonbuk National University Medical School, studied the case of a high school senior in South Korea who tested positive for coronavirus after visiting a restaurant. While recreating the conditions of the day in question, and measuring the air flow, Lee and his team concluded that the virus droplets had been transmitted via the restaurant’s air conditioning unit. Because of the air velocity in the restaurant, the student was infected despite sitting far away from diners carrying the virus. 


© (Korean Academy of Medical Sciences) Diagram of the outbreak at a South Korean restaurant equipped with ceiling-type air conditioners: arrows represent the air flow. Curved air streamlines represent where air is reflected off a wall or barrier, and moves downward toward the floor. (Korean Academy of Medical Sciences)


This study, among others, shows that the official definition of “close contact” (15 minutes, within two meters) is not infallible. People should not become complacent, thinking that social distancing alone is adequate protection, as other transmission factors (such as air conditioning systems) are at play.

There are experts who advocate the use of ventilation, air conditioning, and heating systems during a pandemic – but they do so with “some small reservations”. In some countries, the following measures are required by law:

  • Increase the air exchange rate of ventilation systems
  • Increase the flow of outside air
  • Reduce air recirculation or eliminate it completely
  • Install a particular air decontaminator in systems where it is impossible to turn off or significantly reduce recirculation
  • Increase, to the maximum possible values, the degree of air filtration
  • Increase the total flow of air in areas of human respiration
  • Ensure the flow of clean air to areas protected from polluted air. This can be done by redesigning the location of vents and/or dampers and adjusting the flow rates of supply and exhaust air. This would create a measured differential pressure with an increase in it in the clean zone
  • Locate personnel workspaces in clean ventilation areas that do not interact with higher-risk areas
  • Ensure the maximum operation of exhaust fans in bathrooms during the building’s opening hours


Photo by Markus Winkler on Unsplash


In my opinion, as a specialist in construction climatology, only the final measure outlined above is workable. The other measures are not possible, due to historical, legal, and practical requirements for ventilation systems to provide comfortable conditions for people.

Designers, builders, and operators must work to these requirements and also adhere to accepted traditions and building rules. They must organize the flow of air outside the location of people and/or their workplaces and recreation areas. This approach eliminates the occurrence of drafts, cold (air conditioning), or hot air (air heating) entering occupied places to guarantee comfortable conditions.

This desire to create comfortable conditions makes it dangerous to use central ventilation, air conditioning, and air heating systems in a pandemic, as explained below:

  • When organizing the flow of air outside a person’s location, the hood is always installed above him (his workplace, place of rest, etc)
  • This causes a continuous flow of air (even previously disinfected), the zone of inflow, and the room to collect all the aerosols and pollution which then travel to the hood
  • Inevitably, any biological aerosol coming from outside or from a visitor will hit the person’s lungs

An attempt to meet the previously mentioned requirements means removing the old system and installing a new one. This would be disruptive and costly, as the construction work may involve making holes in load-bearing walls or the roof; laying new air ducts and communications; creating additional power supplies; and more

Specifically, the requirement, “increase in the degree of air filtration”, will not work. This is because of a significant drop (aerodynamic drag of filters) in the multiplicity of air exchange. Such a situation could only be compensated by a more powerful ventilation system, which again would be costly.

Furthermore, “increase the multiplicity of air exchange; increase the inflow of outdoor air; reduce recirculated air”, would be impossible. This is due to the lack of sufficient capacity for processing additional volumes of air when heating or air conditioning is on. Again, this would be extremely costly.

2. Protective, separating screens to ensure safe contact with a potential virus carrier

The practice of installing protective screens in cash register areas and information counters of stores, pharmacies, banks, and other service points originated in China, in response to the first wave of COVID-19. The practice was then introduced in Europe and later in the United States. Now that coronavirus is a global threat, companies everywhere are adopting this affordable, easy-to-install protective measure to safeguard the health and life of employees and prevent the spread of the pandemic.

A solid screen offers effective protection against coronavirus. It does not allow air to flow from the “dangerous” zone to the “clean” zone, equally protecting the employee and the customer. The highest screens, solid or with curved edges, perform well - so long as virus particles cannot penetrate from the sides. Even a small gap would allow air flow to bypass the protection, dramatically reducing its effectiveness.

When a stream of air with droplets released by coughing or breathing hits the screen, it is deflected to the sides, which causes turbulent mixing. This reduces the concentration of the viral aerosol at the location of the infected person. Existing air flows carry the contaminated volume further and thus reduce the proportion of pathogenic particles in the air surrounding the screen.

Though such screens are effective, they do have their drawbacks, which not only impact their advantages but also turn them into a source of danger. Here’s how:

  • The benefits of protective screens are limited to cases of direct exposure only
  • Since existing air flows carry away the contaminated volume, it is then able to spread throughout the room, which poses a hazard to any non-infected people
  • If there are gaps when the screen is installed (such as for transfer of documents or money), there is a flow of air from the “dirty” zone to the “clean” zone. This may occur due to working ventilation, as discussed in point 1
  • If ventilation is disabled or not available, contaminated air can still flow to the “clean” zone by way of natural drafts. Such drafts may be supported by the thermo-gravitational convection of air heated by computers or cash registers
  • In the above two cases, the “protected” person is in a constant flow of polluted air, making him a potential victim of infection


Undoubtedly, and regardless of the current pandemic, it is necessary to implement internal biological protection systems within workplaces. This should include professionally designed and installed ventilation and screens that deliver effective protection.

However, having ventilation installed is a lengthy and costly process; screens are half measures and can be dangerous. This is where VirusStopTech comes in. Our Virus Shield 120 UV air purifier combines the capabilities of ventilation and an effective screen. It is multifunctional, low-cost, and easy to install and operate.

Virus Shield 120

  • Disinfects air in the volume of the entire room
  • Divides the room into “dirty” and “clean” zones
  • Creates a positive-pressure zone at the workplace to prevent the flow of polluted air
  • Supplies large volumes of decontaminated air to the area of human respiration
  • Seamlessly fits into the design of any room

VirusStopTech solutions are effective, reliable, and multibeneficial, making them the ultimate method of protection for you and others.


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