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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 that can range from from a simple cold (several seasonal viruses are Coronaviruses) to more severe pathologies such as MERS-COV or SARS. The new coronavirus has been baptized as SARS-CoV-2 and the disease it causes named COVID-19 by the World Health Organization (WHO). How are these viruses transmitted and how can you protect yourself from them?

What is the difference between a bacteria and a virus?

The bacteria, an autonomous cell

The bacterium is a living micro-organism, composed of a cell, capable of reproducing by simple cell division and having its own metabolism. The human body is home to billions of bacteria and the majority of them are harmless and even useful to our body. Some are nevertheless pathogenic and responsible for infectious diseases. Bacteria can be fought off with antibiotics.

The virus, a parasitic entity

Unlike bacteria, the virus is not an autonomous living organism. It is a kind of intercellular parasite that needs to enter a cell to live and multiply. However, a virus can survive on its own for a few hours in a droplet of water. It is in this form that it is carried by air. Antibiotics have no effect on viruses. The only reliable and effective methods remain prevention to avoid transmission, and vaccination.

Aerosols, a major route of transmission of COVID-19, and other viruses

Viruses and bacteria have similar transmission routes, they enter the body through skin contact, through the food we eat but also, and also, as it is now well known, through the air we breathe.

  • Airway through aerosols: transmission occurs through micro-droplets of nanometric or micrometric size floating in the air, hence the name aerosol. We emit these aerosols when we talk and breathe, in short permanently! They can carry viral loads from infected people for several hours and several meters, depending on the environment, ambient humidity, temperature, air circulation, etc. This transmission route is now recognized as a major route of transmission for some viruses, such as coronaviruses.
  • Droplets : When a person coughs or sputters while speaking, large droplets (“sputum”) are expectorated into the air but remain there for a short time. These droplets can be a route of transmission virus direct to people in the immediate vicinity of the emitter. Viruses can also deposit on surfaces and then be transmitted through skin contact. The hand touches a contaminated surface and is then brought to the face. This transmission route is therefore hybrid between the air route above, and the contact route below.
  • Contact way: infectious transmission occurs through the skin or close contact. The virus can then enter the body through the mouth if an infected hand is brought to the face for example, or through the blood in the event of micro-lesions cutaneous.

As with other viruses, COVID-19 can be transmitted by all of these routes, but in particular by aerosols and the air. as measurements taken at a hospital in Wuhan city in China showed. These measures were published in an article in the prestigious scientific journal Nature from April 20201.A study published in "Science"2 indicates that COVID-19 can remain suspended in the air for several hours. In June 2020, more than 200 researchers from more than 30 countries have united to warn about the importance of the transmission of COVID-19 by aerosols.

purificateur d'air virus

WHO has described the mechanisms of exposure to droplets of COVID-19 and SARSCoV-2 (dark blue color). The light blue color represents the known air suspension mechanisms of SARS CoV -1 and other influenza, for SARS-CoV-2 there is currently no specifically reported evidence (source: AICVF, courtesy Francesco Franchimon).

Airborne transmission of COVID-19 is now widely recognized by the scientific and medical communities. Can air purifiers acting on pollutants in the air help reduce the risk of disease transmission?

Are air purifiers effective against viruses and COVID-19?

As a preamble, note that the first rule to apply in indoor air is to ensure a good ventilation flow : the faster the air in a closed space is renewed, the lower the concentration of viruses released by the occupants of the space will be high. Unfortunately, it is not always easy to ensure a high fresh air change, depending on the ventilation system of the building, exterior noise or the weather if you have to open the windows, etc. Hence the interest of air purifiers to provide additional safety.

In September, the Working Group on air purifiers of the FIMEA association (Interprofessional Federation of Atmospheric Environment Trades) sent public authorities an open letter declaring:

“(...) all over the world, air, ventilation and air conditioning professionals have stressed the importance of including indoor air treatment in the fight against the coronavirus. They have made recommendations on this point in various documents and reports, always based on the current state of knowledge. (...) In view of all these elements, it seems that acting on indoor air in general is a public health issue and a key factor to be taken into account in the fight against Covid-19. In fact, the use of devices such as air purifiers / purifiers provides real prevention solutions. ”

On September 12, the Auvergne-Rhône-Alpes Region announced the equipping of schools with air purifiers, considered"The blind spot in the fight against Covid-19 in France, as numerous studies prove that air is a vector of propagation."

In practice, an air purifier reduces the average concentration of particles in the room, including that of aerosols emitted by human speech and breathing, which are just one form of particles. The average risk of virus transmission can therefore be considered to be reduced by air purifiers. Meanwhile, the "average" reduction of aerosols is not a guarantee of non-transmission of viruses, and the effectiveness depends greatly on the implementation... Let's detail this below!

What air purification technology can be used to eliminate viruses, and COVID-19 in particular?

To judge the efficiency of capture of an aerosol by air purification technologies, the size of the particles suspended in the air must be taken into account. Bacteria are mostly 1 to 10 micrometers (written µm - 1 to 10 thousandths of a millimeter) while viruses have an average size of 10 to 400 nanometers, or 10 to 100 times smaller! These pathogens are 100 to 10,000 times smaller than a grain of sand!According to a study published in the British medical scientific journal The Lancet COVID-19 has a relatively large size for a virus: 100-150 nm which corresponds to 0.1 - 0.15 micrometers.

However viruses do not travel "alone" in the air, they are carried by micro-droplets of water that are commonly estimated to be less than 5 microns in size. Measurements carried out in a hospital in the city of Wuhan in China, published in the journal "Nature" 1, show a wide spectrum of aerosol sizes, ranging from a few tens of nanometers to several micrometers:

purificateur d'air virus

HEPA-type “mechanical” filter devices are normally capable of capturing aerosols which pass through the filter. However, they obviously cannot capture aerosols from the air that does not pass through the filter, a renewal rate of significant air (minimum 1 volume per hour) is therefore necessary to obtain a significant reduction. However, the air circulation induced by the filter purifier will induce air speeds in the room which could, on the contrary, accelerate the displacement of aerosols carrying viruses and thus possibly increasing the risk of transmission. It is therefore very difficult to rule on the real effectiveness of such a device on virus transmission.

Other technologies recognized as biocides are used to replace or complement filters: UVC, photocatalysis, ozone, cold plasma. These technologies all present risks of emission of so-called secondary pollutants which are potentially harmful to health. We recommend their use in unoccupied spaces, which makes their usefulness in the fight against virus transmission doubtful ...

Effectiveness of TEQOYA air purifiers on viruses, including Covid-19

Can TEQOYA ionizer air purifiers be effective against viruses, and in particular against the SARS-CoV-2 coronavirus responsible for the COVID-19 pandemic? We have many experimental results to suggest that our devices reduce the viral load of the air in spaces equipped with:

1- They were tested on a large sample of particles of various sizes, up to 7 nanometers. The performance tests of our devices show their effectiveness, including on nanoparticles.

2- TEQOYA air purifiers have been tested on bio-contaminants, viruses and bacteria, in several laboratories. The results show a very clear elimination of around 90% of bacteria from the air:

3- These results were recently corroborated for viruses, using an innovative test protocol to assess the reduction in viral load in infected air. A 75% reduction in the virality of aerosols infected with the H1N1 influenza virus was thus measured! Another study, published in the journal Nature,shows the strong reduction in the spread of a virus through the use of an air ionizer3.

4- We have more results showing the rapid reduction of micro-droplets of water which are the vector of virus transmission by air.

purificateur d'air virus

purificateur d'air virus

Aerosol reduction measurement in the laboratory of the University of Rome Sapienza

TEQOYA's air ionization technology can therefore be useful in reducing the risk of transmission of infections by the air, just as it reduces the density in the air of many particles (combustion residues, mineral residues , liquid phase of semi-volatile organic compounds).

The additional advantages of TEQOYA air ionizers

Beyond their ability to clean up, TEQOYA air ionizers have other practical advantages compared to other air purification technologies, to fight against the transmission of viruses and COVID in particular. Some explanations :

Ionization increases the filtration efficiency of masks. According to a scientific study carried out by American and Korean laboratories. Aerosol and Air Quality Research), air ionization increases the effectiveness of masks. TEQOYA has just completed an independent laboratory test, measuring a 30% reduction in particles passing through a surgical mask. There is therefore a synergy between masks and air ionizers making it possible to further reduce the risk of transmission of infection.

A "classic" filter air purifier, by the air circulation that it induces by a fan, is likely to accelerate the movement of infected aerosols and can therefore potentially increase the risk of transmission. The WHO has notably warned about the use of ventilators in closed rooms in the context of Covid-19. A fanless air ionizer such as those from TEQOYA, on the contrary, does not encourage the mobility of the aerosols present. in the air.

purificateur d'air virus

"Classic" filter air purifier

purificateur d'air virus

TEQOYA Air purifier ionizer

All these elements suggest that the use of ionizer air purifiers can be an effective complementary solution to the barrier gestures recommended by the medical authorities, in particular regular hand washing and wearing a mask, to reduce the risk of transmission, especially in a space with a high occupancy rate, or between people standing in close proximity to each other.

Sources :

  • 1Liu, Y., Ning, Z., Chen, Y. et al. Aerodynamic analysis of SARS-CoV-2 in two Wuhan hospitals. Nature 582, 557-560 (2020)
  • 2Kimberly A. Prather, Linsey C. Marr et al. Airborne transmission of SARS-CoV-2. Science 16 Oct 2020: Vol. 370, Issue 6514, pp. 303-304
  • 3Hagbom, M., Nordgren, J., Nybom, R. et al. Ionizing air affects influenza virus infectivity and prevents airborne-transmission. Sci Rep 5, 11431 (2015).

TEQOYA now has independent laboratory tests for viruses. Write to us at to know more.


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