Aerosols and COVID-19

Do you remember what your life was like before the pandemic? It may not be easy for you because the months following the detection of a new virus have undoubtedly changed almost everything. The arrival of the coronavirus has transformed many customs and made us aware of how vulnerable the collective lifestyle is.

Furthermore, in this context, new concepts have been incorporated into our everyday vocabulary, as well as previously unexplored concerns. Therefore, it is very interesting to delve deeper into the relationship that exists between aerosols and COVID-19 and, at the same time, how it is possible to breathe cleaner air through different safe alternatives.

What are aerosols and how do they spread?

It is a highly contagious virus, as it is transmitted through small liquid particles expelled by the infected person through the mouth or nose. This small gesture can happen when talking, but also when breathing, singing, sneezing, coughing, or blowing. Moreover, its size is not homogeneous, but rather variable. In that case, they are called respiratory droplets or aerosols.

In this sense, according to the World Health Organization (WHO), the coronavirus primarily spreads through the aforementioned aerosol particles. One of the factors contributing to this relates directly, among many other reasons, to not maintaining the already famous interpersonal safety distance of at least 2 meters apart.

On the other hand, the Spanish Ministry of Health believes that temperature and relative humidity (RH) can be considered modifiable risk factors in the transmission of COVID-19. That is to say, the virus is more stable at low temperatures and respiratory aerosols, as the main carriers of the virus, remain suspended longer in dry air.

How aerosols influence the transmission of COVID-19

Additionally, people must be very close for a certain period. There were many doubts and conflicting opinions at one point, but to this day, the scientific community agrees that aerosols and COVID-19 maintain a direct link.

Similarly, although there is a possibility of transmission due to its presence for hours, or even days, on certain surfaces, it is not usually the most common way.

However, in some cases, the origin can be traced back to a simple action, for instance, when a person with coronavirus sneezes, coughs, or even talks over a certain material. Subsequently, if another person touches it and rubs their eyes, nose, or mouth, they could catch the virus. For this reason, it is so important to wash hands frequently.

On another note, before moving forward, we want to delve a little deeper into the differences that exist between droplets and aerosols. Both particles are emitted when talking, shouting, coughing, or sneezing, although they present some differences.

Droplets usually spread infection by impacting the eyes, nostrils, and mouth, as they manage to travel between 1 and 2 meters. Meanwhile, aerosols transmit the disease through inhalation. They can also be projected to a similar distance, although we can consult studies that claim they have the ability to travel up to 8 meters, however incredible it may seem. This is because, being smaller, they can more easily enter the lungs.

In fact, precisely because of their ability to reach these organs, aerosols are believed to cause the most severe coronavirus symptoms, although this point is still not entirely clear and will require further scientific study.

Why is ventilation so important to break the link between aerosols and COVID-19?

The extra that we mention in the previous paragraph is related to ventilation. It is essential to eliminate, as much as possible, the tiny particles that are suspended in the air and can carry the coronavirus. If not, they could infect healthy people present in the same enclosed space as the infected individual(s). That’s why it is so important that, whenever possible, meetings with non-cohabitants are held outdoors.

However, this situation is not always possible, and that’s where ventilation comes into play. In addition to ventilating frequently by opening windows, it is also important to have a ventilation system. Below, we review some of its main functions:

• Air renewal. With an adequate ventilation system, the air circulating inside a room is expelled. This allows fresh air to enter. The renewal process enhances its properties while improving the odor and increasing the wellbeing of the people present in the space.
• Filtering particles. In optimal conditions, both for indoor and outdoor.
• Conditioning the air. Ventilation systems are also used to maintain appropriate levels of humidity and temperature..

Types of ventilation against aerosols

• To allow the maximum amount of clean outdoor air into an enclosed space. Ventilation systems should facilitate this process simply.
• Analyzing the risk of contagion by measuring CO2 concentration. These parameters help assess whether air cleanliness is adequate.
• Using filters. For example, HEPA filters are a guarantee of clean, purified air, although there are other options depending on the type of mechanical ventilation systems used and their utility. It's not the same application in domestic settings as it is in professional environments or large constructions.

Natural ventilation against aerosols

Mechanical ventilation against aerosols

Furthermore, for it to be an effective system, it needs periodic checks and maintenance processes. Additionally, it is very useful to have a CO2 meter that certifies that the operation is as expected and the treated air is in optimal conditions.

Ventilation in large capacity enclosed spaces

However, when specific protection measures cannot be adopted, it is essential to have a good mechanical ventilation system. In this case, it should be combined with a CO2 meter to closely monitor air quality and, if possible, with specific and persistent natural ventilation actions.

Best practices to avoid aerosol transmission

Although it is true that, for now, zero risk does not exist, if you take into account the following precautions and best practices, the chances of contagion decrease. They are as follows:

• Maintain at least one and a half meters of distance from others, whether they are healthy or not.
• Wear a mask when going out in public and whenever you are in enclosed spaces with other people.
• Think very carefully about where you will go, how long you will stay in each place, and who you will be with.
• Wash your hands frequently. When you can’t do it with soap and water, use a solution of alcohol-based hand gel.
• Avoid touching surfaces when you are outside. If you do, disinfect your hands with alcohol gel and do not touch your eyes, nose, or mouth.
• If you must be in closed spaces with people with whom you do not live, ventilate continuously with a mechanical ventilation system, ensuring a high frequency of air renewal.
• If you cough or sneeze, cover your face with a disposable tissue and dispose of it as soon as possible. If you don’t have one on hand, do it in the inner elbow of your arm.
• When speaking loudly or singing, more aerosols are emitted than when remaining silent or speaking softly. Thus, a simple and effective measure to reduce the risk of contagion is silence. There are spaces where this is easily applied, like in public transport or inside waiting rooms.