What are aerosols and how to avoid the risks of transmission of COVID-

Hecontagion of Covid-19 through aerosols has been published by the Ministry of Health after the warnings that more than a hundred scientists communicated to the WHO since the beginning of this pandemic, urging the recognition of the risks.

This data is also collected in thescientific report of the World Health Organization, where the scientific evidence on the transmission of SARS-Cov-2 through the air is recognized.

To understand the risk involved andhow we can do to protect closed environments such as schools, shops or hospitals, we first define youwhat are aerosols and how they influence the spread of the coronavirus.

What are aerosols

Aerosols are solid or liquid particles that are suspended in the air.

These particles are produced when the respiratory droplets that humans emit when we breathe, speak, sneeze, cough or sing, mix with the surrounding air and form an aerosol.

The size of these droplets varies depending on how and where they are produced in the airways. For example, when we cough we generate a greater number of drops than when we speak. But beware, when we have a conversation for only two or three minutes, we already begin to produce the same amount of drops as when we cough.

If they are larger drops, they quickly fall to the ground. But if they are smaller than 5 microns, thatthey are usually the ones we give off when we breathe, they can stay in the air for longer.

Aerosol transmission of SARS-CoV-2

In the size of the droplets that make up the aerosols is where therisk of virus transmission by aerosols. Because, research has shown,droplets smaller than 5 microns can remain suspended in the air for hours.

Therefore, airborne transmission becomes highly dangerous in a closed room that is poorly ventilated with an infected person or after this person has coughed there.

When someone sneezes or coughs, they expel larger droplets that quickly fall to the ground. But, when someone speaks or breathes, they throw small droplets into the surrounding air that, due to their low weight, floats for longer in the environment and makes it more dangerous in the face of coronavirus contagion.

This is why there is strong evidence that they can carry live viruses if the person is infected.

COVID-19: Assessment of the risk of transmission of SARS-CoV-2 by aerosols. Prevention measures and recommendations

According to the document published by theMinistry of Health, Consumption and Social Welfare that collects thework of a group of experts on aerosols and transmission and prevention of infectious diseases, it is considered thatSARS-CoV-2 is transmitted by aerosols containing viruses generated by an infected person in a closed and poorly ventilated space.

This same document includes an evaluation of the risk of transmission by aerosols as well as a series of attitudes that reduce the emission of aerosols by people and recommendations for the prevention of the transmission of SARS-CoV-2 through the air.

Attitudes that reduce the emission of aerosols by people

As we mentioned earlier, singing or speaking loudly emits more aerosols thanwhen speaking softly or remaining silent.

Therefore, one of the recommended attitudes that are included in the official document of the Ministry of Health, is silence in public transport or waiting rooms.

Another recommended attitude forreducing the emission of aerosols is that, inplaces like restaurants where it is not possible to use the mask while eating, keep noise levels low in order to reduce people's tone of voice.

Summary of recommendations to reduce the transmission of SARS-CoV-2 through aerosols in indoor spaces

As stated in the official document published by theMinistry of Health, Consumption and Social Welfare,These are the recommendations, in summary, to reduce the transmission of coronavirus through aerosols in indoor spaces:

1. Natural or mechanical ventilation of interior spaces
   1. Air conditioning systems must avoid air recirculation
   2. Air conditioning systems must maximize the intake of outside air
   3. Perform natural cross ventilation to ensure the renewal of indoor air with outdoor air
   4. Avoid airflows between people in poorly ventilated indoor environments that can carry aerosols emitted by infected people.
   5. Comply with the recommendations for operation and maintenance of the air conditioning and ventilation systems of buildings and premises according to current regulations and the Recommendations of the Ministry of Health and professional organizations.
   6. For any ventilation system a minimum ventilation by supplying outside air of 12.5 liters / second / person is recommended. Upper ventilation is recommended when the activity carried out implies high emission of aerosols, for example. intense exercise, singing, etc.).
   7. CO2 meters can help check if ventilation is adequate and should be used at the discretion of maintenance technicians and the needs of the premises or building.

2. Bioaerosol retention and air purification
   1. Air filtration: use air filters with the highest possible efficiency ensuring the recommended air flow and according to the specifications of the ventilation system.
   2. When the above measures cannot be applied, autonomous purification systems with HEPA filters can be used.
   3. Germicidal treatments: exceptionally and in indoor environments where the air cannot be ventilated, filtered or purified, and where situations with a higher risk of transmission are generated, the use of germicidal treatments can be considered.

How to avoid the spread of coronavirus by aerosols

In conclusion and in view of the evidence found so far, theMinistry of Health establishes what:

• Aerosols generated by people with active SARS-CoV-2 infection contain viable viruses.
• The viruses contained in aerosols have the ability to generate infection, especially in circumstances such as close proximity to the infected person for a long time in closed and poorly ventilated spaces.
• There is consistent scientific evidence that allows us to affirm that the transmission of the SARS-CoV2 virus by aerosols should be considered a route of transmission "..

For all the above, it is recommendedventilation and air purification in closed spaces and, in public places such as schools, hospitals, restaurants, shops and businesses, the use of aCO2 meter to monitor carbon dioxide levels at all times in the environment and indoor air health.