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COVID-19: are air purifiers effective against virus transmission?

In December 2019, a respiratory virus from the Coronavirus family appeared in the Wuhan region of China and has since spread to all continents. Coronaviruses are a large family of viruses causing illnesses ranging from the common cold (several seasonal viruses are Coronaviruses) to more severe diseases such as COVID-19 or SARS. The new Coronavirus identified in January 2020 was called SARS-CoV-2. How are these viruses transmitted and how can we protect ourselves from them? That is what we will see in this article.

First of all, what is the difference between bacteria and virus?

Bacteria, autonomous cells

A bacterium is a living microorganism consisting of a single cell. It is capable of reproducing by simple cell division and has its own metabolism. The human body is home to billions of bacteria, the majority of which are harmless. Some are nevertheless pathogenic and responsible for infectious diseases. Bacteria can be fought with antibiotics.

The virus, parasitic entities

Unlike bacteria, a virus is not an autonomous living organism. It is a kind of intercellular parasite that needs to enter a cell to live, grow and multiply. Antibiotics have no effect on viruses. The only reliable and effective methods are prevention and vaccination.

How are they transmitted?

Viruses and bacteria are transmitted in much the same way, they enter the body through wounds, food, close contact and the air we breathe. There are 4 routes of transmission:

  • Airborne: transmission by droplets of saliva or aerosols from respiration. When a person breathes, talks or coughs, micro-droplets travel through the air and can stay there for several hours. These droplets can carry the virus to another person's respiratory system ;
  • Oral: transmission by eating or drinking contaminated food ;
  • Blood: transmission through accidental wounds, due to skin breaks, blows or wounds, bites or stings ;
  • Route of contact: Infectious transmission through the skin or close contact.
  • As with other viruses, COVID-19 can be transmitted by air and hand contact. One of the most important transmission factors appears to be contact with unwashed hands and contact with contaminated objects. The airway is considered the main transmission of the virus. The most common symptoms of COVID-19 are fever, fatigue and a dry cough. Some people may also experience aches, headaches, tightness or shortness of breath. These symptoms may later lead to an acute respiratory infection or radiologically detectable lung abnormalities. This is why it is necessary to call the health services for people at risk.

What can you do to protect yourself?

The WHO recommendations to prevent the spread of infection are as follows:

  • Wash your hands regularly with soap and water or use a hydroalcoholic solution;
  • Avoid touching your eyes, nose or mouth;
  • Wear a mask when physical distancing is not possible.
  • When coughing or sneezing, cover your mouth and nose with your bent elbow or use a disposable tissue and dispose of it;
  • Avoid eating raw meat and avoiding contact with wild animals;
  • Avoid close contact with anyone with flu-like symptoms.

Can an air purifier be effective against viruses, especially the coronavirus?

As with all air purification technologies, an important factor to consider when judging the capture efficiency of an aerosol of any kind is: its size. A quick reminder of the differences in size between bacteria and viruses: most bacteria measure from 1 to 10 micrometers (written µm - 1 to 10 thousandths of a millimeter) whereas viruses have an average size of 10 to 400 nanometers, 10 to 100 times smaller! These pathogens are 100 to 10,000 times smaller than a grain of sand!

Can TEQOYA air purifiers be effective on such small particles? The answer is yes. They have been tested over a wide range of particle sizes, down to 7 nanometers, and also on bacteria. The results show a very clear elimination of bacteria from the air, with an efficiency rate of about 90%:

These results show that TEQOYA's air ionization technology is effective on microorganisms, as well as on many types of particles (combustion, minerals, micro-droplets). A study conducted by the U.S. National Institute for Molecular Biological Information also demonstrates the benefits of air ionization. This technology can be used to prevent airborne infections with the COVID-19 virus. The performance tests of the devices show a very uniform efficiency even on nanoparticles.

Efficiency range of TEQOYA air purifiers according to particle size

COVID-19 has a relatively large size for a virus: 100-150 nm which corresponds to 0.1 - 0.15 micrometers, according to a study published in the British medical scientific journal "The Lancet". The size of the virus is close to the median of the particle sizes for which TEQOYA air purifiers have most often been tested with an efficiency similar to that found for bacteria-sized particles. There is therefore no doubt about the ability of air purifiers to reduce the concentration of COVID-19 in the air, with a level of performance close to those measured on bacteria.

Behavior, masks and air purifiers: what to do?

It is of course essential to apply the precautions recommended by the WHO and the public authorities, to protect ourselves but also to protect those around us from the virus.

Masks can be an effective protection against transmission of the virus by air. Their effectiveness depends strongly on their characteristics and especially on the way they are worn. The mask must be fitted correctly, as protection depends on the tightness of the face. It is therefore more effective to properly adjust the mask to prevent leaks than to use a poorly adjusted high filtration mask N95 (Noti JD, Lindsley WG, Blachere FM, et al. Clin Infect Dis 2012). In addition, according to a scientific study carried out by American and Korean laboratories (Lee, Byung & Yermakov, Mikhail & Grinshpun, Sergey. (2005). Aerosol and Air Quality Research), the air ionization increases the effectiveness of masks.

Air purifiers, on the other hand, make it possible to reduce the average concentration of viruses present in the air. On the other hand, pay attention to which purifier you choose. COVID-19 is 0.1 microns in size and can spread quickly from person to person by floating in the air. The air purifier must be able to either retain it or deactivate it while it is in the air.

It is reasonable to think that this lower concentration reduces the likelihood of transmission between people. However, it is important to note that this does not eliminate the risk of transmission, especially in a space with a high occupancy rate, or between people standing close to each other.

TEQOYA has now laboratory results on viruses. For details, email us at

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