The importance of aerosols in the spread of coronavirus is currently the subject of intense research. In fact, institutions such as the Hermann Rietschel Institute of the Technical University of Berlin have been researching the spread of aerosols for years.

Among the recommendations established since the beginning of the COVID-19 spread, great importance has been given to ventilation systems. This is because rooms with ventilation systems often meet air quality limits better than rooms with window ventilation.

Back to school in times of coronavirus
Back to school in times of coronavirus

As soon as a person enters an enclosed room they pollute the air quality. In addition to the fact that he or she constantly emits carbon dioxide (CO2), he or she also breathes in a variable amount of aerosols. The number of these depends on the level of pollution in the room.

Indoor air quality indicators

For 130 years, the Pettenkofer limit value has been used as an indicator of air quality. According to this indicator, a CO2 concentration above the limit value of 1,000 ppm can cause headaches, fatigue, and concentration difficulties. In particular, places with clean air have levels between 360 and 500 ppm.

In this respect, ventilation plays a key role in keeping CO2 levels below the limit value. In fact, Martin Kriegel, director of the Hermann-Rietschel-Institut, says that not all workplaces, offices or schools have adequate ventilation.

The concentration of aerosols in enclosed spaces is often linked to the concentration of CO2. “Small, poorly ventilated or unventilated rooms have a higher risk of transmitting SARS-CoV-2”.

Lack of government preparation for return to classrooms and offices

Aerosols are microscopic droplets that remain suspended in the air for long periods of time. These particles – solid or liquid – were listed on 9 July by the World Health Organization (WHO) as a potential source for VIDOC-19 infection.

The importance of airborne aerosols in coronavirus transmission
The importance of airborne aerosols in coronavirus transmission

However, masks are not the right solution for closed spaces. Aerosols are less than five microns in size and follow the airflow. This is why 90% of them come out at the edges of the mask, as indicated by the Hermann Rietschel Institute.

Fighting the virus will require more measures because it is increasingly clear that it is not just direct person-to-person contact through things like coughing that is spreading the pathogen. It can also float in the air, which can defeat efforts at social distancing.

” Daily face masks barely stop the aerosols. Aerosols emitted by humans are less than 5 microns and follow the airflow. They escape almost completely through the edges of the mask.”

Martin Kriegel director del Hermann Rietschel Institute

The director of this Institute states that there are two measures that should be carried out in closed spaces:

Risk in gyms is high

When a person sneezes or coughs the risk increases. Talking loudly, yelling or singing also increases the number of aerosols emitted, thus increasing the risk. However, the risk is even greater in gyms, as physical exercise doubles the generation of aerosols.

El riesgo es todavía mayor en gimnasios, ya que el ejercicio físico duplica la generación de aerosoles.
The risk is even greater in gyms, as physical exercise doubles the generation of aerosols. The risk is even greater in gyms, as physical exercise doubles the generation of aerosols.

Aerosols are not as scary when they are outdoors because the wind blows them away quickly and the sun can destroy the virus. Indoors, however, this does not happen. Researchers have shown that infectious aerosols can travel many meters and survive for minutes or even hours indoors.

What strategies are proposed?

Physicists, engineers and environmental technicians are looking for ways to combat flying viruses. The good news is that, surprisingly, there are numerous defensive strategies that are both effective and feasible. However, most of them cost money – and require people to change their behavior.

“Ventilation is essential”

Detlef Lohse, German physicist, Professor of Fluid Mechanics at the University of Twente

The simplest remedy for indoor sprays has always existed, and it’s free. “Ventilation is essential,” says physicist Lohse. If you ventilate well and provide plenty of fresh air, you can quickly reduce the number of aerosol particles floating around.

La ventilación es esencial para reducir el número de partículas de aerosoles

But ventilation also has its difficulties. If there is little wind outside or little difference in temperature between inside and outside, natural ventilation will only work to a certain extent. It is not enough to keep the windows permanently open.

It also recommends that classrooms be equipped with CO2 measurement devices. If the values are too high, it is also an indication that the aerosol concentration is too high and the room should be ventilated.

In the last few weeks Christian Kähler, physicist and professor of fluid dynamics at the University of the Federal Armed Forces in Munich (who has spent 25 years researching aerosols), has been verifying the operation of air filtration and purification devices for COVID-19.

The physicist believes that these devices could be the solution for the safe operation of restaurants, shops, offices, and schools, especially in winter when ventilation becomes even more difficult.

“If you keep this system running constantly, no one will be able to create an aerosol concentration at an infectious level in a room.”

Christian Kähler, physicist and professor of fluid dynamics at the University of the Federal Armed Forces in Munich

More information about this at: Scientists Weigh the Benefits of Air Purifiers in Fighting COVID-19

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