What Is Aerosol?

What is aerosol? 

Aerosol is not just a phenomenon related to viruses, but a common physical phenomenon. It refers to all solid and liquid particles (0.001-100 microns in diameter) suspended in gas (such as air), which can contain soil particles, industrial dust particles, particles emitted by automobiles, bacteria, microorganisms, and plant spore powder. It can be said that the whole earth, or around us is an "aerosol world".

How is it produced?

Aerosols can be produced naturally. For example, clouds, fog, haze, and dust floating in the air are all aerosols. These aerosols may enter our bodies through breathing.

Aerosols can also be formed artificially, such as droplets produced by sneezing and coughing. Large droplets quickly fall on the ground or the surface of objects and often become direct (droplets) transmission; while tiny droplets (usually less than 5 microns in diameter) can be spread in Suspended in the air for a period of time, and travels farther with the airflow, it is an aerosol.

What is aerosol transmission?

If some viruses are contained in the aerosol of these small particles (usually less than 5 microns in diameter), as the liquid evaporates, the infectious viral nucleic acid is finally left to form a droplet nucleus, which can float to a distance in the form of aerosol , Causing long-distance transmission, which is also the cause of aerosol transmission in infectious diseases that everyone is currently worried about. 

How far is the aerosol from us? 

Aerosol transmission is a way of airborne transmission. People are immersed in aerosol all the time.

For example, people talk face to face, sing songs or look at each other in a crowded, confined space. Everyone inhales the aerosol particles exhaled by the other person.

Even in a closed space without gas flow, such as indoors and corridors, aerosols will still float in the air for a long time with the help of the Brownian motion characteristics of particles.

The significance of epidemiology is that people who are susceptible to infection may be infected by inhaling virus-containing aerosol particles suspended in the air without meeting the sick person. 

Know that aerosols are important, but don’t talk about aerosol discoloration!

Don't panic! Although aerosol is easy to form, it is not easy to infect people

Since the general aerosol particles are relatively large, the ones larger than 10 micrometers and 50 micrometers are the most, and general medical masks can block them. Very small aerosol particles (with a radius of less than 0.1 micron), light weight, and mainly distributed in high altitude (from the soil close to the ground), they will drift away with the wind, and the possibility of being breathed by people is unlikely.

The farther away from the source of the disease, the virus concentration will continue to drop

In addition, the virus aerosol will also "inactivate" in the air. When the virus leaves the body fluid and floats in the air, the living environment changes and it is more likely to die. In addition, there are ultraviolet rays and free radicals in the air, which can kill viruses or reduce toxicity. For example, in an open space, even if someone expels a lot of viruses in one breath, they are easily diluted in the air, and the virus concentration will be reduced to a safe limit, making it difficult to infect people.

And as early as 2009, after the H1N1 influenza A outbreak in the United States, some researchers conducted a detailed analysis of the aerosol transmission of influenza viruses, and finally proved that: for influenza viruses, the probability of aerosol infection is much lower than the probability of direct infection. Please don't panic too much.

In other words:

As long as the location where the aerosol itself is relatively low (the smog is lighter), it is relatively safe.

As long as there is no epidemic virus in the aerosol, it is relatively safe.

As long as the place is located, the concentration of the epidemic virus in the aerosol is relatively low and relatively safe.

So, when should we be wary of aerosol transmission?

In an unventilated environment, aerosols containing viruses will stay in the air for a long time. For example, after a patient takes an elevator, there will be aerosols of the virus in the elevator, and due to poor air circulation, if a healthy person subsequently enters the elevator, the risk of infection will increase. 

In addition, virus-containing aerosols may enter the room along relatively closed circulation systems such as central air-conditioning systems and sewer systems. Special attention should be paid to the central air conditioner of the all-air system. The air in different rooms will cross flow, which is easy to cause cross-contamination. 

During the epidemic, how should we protect ourselves?

After the above introduction, I believe that everyone also has a deeper understanding of aerosols. Please don't panic too much, but you can't take it lightly. [Baiqing Editor] I would like to remind everyone to take the following protections during the epidemic:

　　 1. Cancel gathering activities and avoid going to confined places for activities.

　　2. Open more windows for natural ventilation.

　　 3. The elevator room has poor ventilation and a small space. Be sure to wear a mask in the elevator and touch it carefully.

　　4. Wash your hands frequently, scrub frequently, and keep away from others.

　　 5. Pay more attention to the bathroom. When flushing the toilet, close the toilet lid and flush again. During the epidemic, pay attention to the dredging and disinfection of sewers.

　　 6. Don't spit on the ground, let alone tramp on the sputum on the ground with your feet.